| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Sleep and Cognitive Neuroscience Laboratory, Department of Psychiatry, Boston University School of Medicine, Boston, Massachusetts
Submitted 8 March 2007; accepted in final form 3 April 2007
 |
ABSTRACT |
|---|
|
183 min; however, the suppression of REM sleep by baclofen was prevented by a subsequent microinjection of SpCAMPS. These results provide evidence that the activation of cAMP-PKA within the PPT can successfully block the GABAB receptor activation–mediated REM sleep suppression effect. These findings suggest that the PPT GABAB receptor activation–mediated REM sleep regulating mechanism involves inactivation of cAMP-PKA signaling in the freely moving rat. |
|
INTRODUCTION |
|---|
|
; Deurveilher and Hennevin 2001; Garcia-Rill 1997; Kobayashi et al. 2004a,b; Zhang et al. 2005). The PPT, situated in the dorsolateral mesopontine tegmentum, contains a prominent group of cholinergic and some noncholinergic neurons, which project widely throughout the brain stem and forebrain (for reviews, see Datta 1995; Garcia-Rill 1991; Jia et al. 2003; Jones 2004; Lai et al. 1993). Single cell recordings from the PPT/LDT of behaving cats and rats have identified several different types of cells whose firing rates correlate with both wakefulness and REM sleep (Datta 1995; Datta and Siwek 2002; El-Mansari et al. 1989; Steriade et al. 1990; Thakkar et al. 1998). Some of the recent pharmacological studies in cats and rats have shown that the activation of PPT kainate type glutamate receptors induces REM sleep (Datta 2002; Datta and Siwek 2002; Datta et al. 2002). Other studies have shown that the activation of PPT GABAB receptors inhibit PPT REM-ON cells activity and suppresses REM sleep (Datta et al. 2003; Ulloor et al. 2004). Despite tremendous progress in the identification of specific neurotransmitters and receptors involved in the regulation of the PPT cells neuronal activity and REM sleep, very few attempts have been made to study the possible intracellular signal transduction mechanisms of the PPT that may be involved in the regulation of REM sleep.
It is known that the GABAB receptors couple to Gi/Go G proteins (Couve et al. 2000; Kerr and Ong 1995; Mody et al. 1994; Robbins et al. 2001; Sivilotti and Nistri 1991; Takahashi et al. 1998; Thompson 1994). It is also known that Gi/Go G proteins inhibit adenylyl cyclase (AC) and inhibition of AC prevents activation of the cAMP-protein kinase A (PKA) signal transduction pathway (Gilman 1987; Marinissen and Gutkind 2001). Because it has been shown that the activation of GABAB receptors within the PPT suppresses activity of REM-ON cells and REM sleep in the freely moving rat (Ulloor et al. 2004), it is reasonable to suggest that the PPT GABAB receptor activation–induced suppression of REM sleep may have been caused by the inhibition of AC that ultimately prevented activation of cAMP-PKA. In support of this suggestion, two recent studies have shown that the local application of drugs that inhibit AC activity and cAMP-PKA activation in the PPT suppress REM sleep (Bandyopadhya et al. 2006; Datta and Prutzman 2005). Although these two studies have shown that the inhibitions of both AC and cAMP-PKA activation in the in the PPT suppresses REM sleep (Bandyopadhya et al. 2006; Datta and Prutzman 2005), no studies have shown that the activation of either AC or cAMP-PKA in the PPT could increase REM sleep. It has also not been shown that the GABAB receptor activation–mediated REM sleep suppression effect could be rescued and/or bypassed by the activation of intracellular cAMP-PKA.
In this study, I examined the changes in sleep-wake behavior of freely moving rats after activation of cAMP-PKA, GABAB receptor, or both cAMP-PKA and GABAB receptor within the PPT. Our results show that the activation of PPT cAMP-PKA induces REM sleep. Although activation of PPT GABAB receptors suppresses REM sleep, these results also show that the activation of cAMP-PKA could rescue REM sleep from the GABAB receptor activation–induced suppression. The results of these experiments indicate that, in the PPT, GABAB receptor activation–mediated REM sleep regulation involves inactivation of the cAMP-PKA system.
|
|
METHODS |
|---|
|
Experiments were performed on 28 adult male Sprague-Dawley rats (Charles River, Wilmington, MA) weighing between 250 and 350 g. The rats were housed individually at 24°C with food and water provided ad libitum with lights on from 7:00 AM to 7:00 PM (light cycle) and off from 7:00 PM to 7:00 AM (dark cycle). The principles for the care and use of laboratory animals in research, as outlined by the National Institutes of Health Publication no. 85–23 (1985), were strictly followed.
Drug and vehicle for microinjections
In this study, GABAB receptors in the PPT were activated by a GABAB receptor–specific agonist, baclofen hydrochloride (baclofen; molecular weight: 250.13), purchased from Sigma Chemicals (St. Louis, MO). The selection of baclofen was based on the selective agonistic effects on GABAB receptors (Bowery 1993; Enna and Maggi 1979; Falch et al. 1986; Fromm et al. 1990; Hill and Bowery 1981; Hong and Henry 1991; Kerr and Ong 1995; Misgeld et al. 1995; Paredes and Agmo 1989; Ulloor et al. 2004). In addition to specificity, the above studies have shown that baclofen is readily soluble in water and accessible to extracellular receptors. Baclofen was dissolved in 0.9% saline to make 1.5 nmol/100 nl dose. The optimum dose of baclofen (1.5 nmol/100 nl) was predetermined from an earlier dose-response study (Ulloor et al. 2004). Another drug used in this study was an activator of cAMP-PKA activity, Sp-cAMPS triethylamine (SpCAMPS; molecular weight 446.46), also purchased from Sigma Chemicals. The selection of this drug was based on the selective activation effect on intracellular cAMP-PKA activity (Capece and Lydic 1997; Cook et al. 1995; Punch et al. 1997; Wang et al. 1991). In addition to the selectivity, SpCAMPS was suitable for this study because these studies have shown that it is water soluble, cell membrane permeable, has reversible effects, and has been used successfully in microinjection studies in behaving animals (Capece and Lydic 1997; Cook et al. 1995; Punch et al. 1997; Wang et al. 1991,1993). SpCAMPS was dissolved in 0.9% saline to make 1.5 nmol/100 nl dose. This 0.9% saline (100 nl) was also used for the vehicle control microinjection. Control saline and drug solutions were freshly prepared under sterile conditions before each use.
Surgical procedures and implantation of electrodes
Treatment of the animals and surgical procedures were in accordance with an approved institutional animal welfare protocol (AN-14084). Efforts were made to minimize the number of animals used and their suffering. Rats were anesthetized with pentobarbital sodium (40 mg/kg, ip), placed in the stereotaxic apparatus, and secured using blunt rodent ear bars (Paxinos and Watson 1997). With the use of sterile procedures, cortical EEG, dorsal neck muscle EMG, and hippocampal EEG (to record theta waves) recording electrodes were chronically implanted, as described elsewhere (Datta 2000). In addition, a stainless steel guide tube (26 gauge), with an equal-length stylett inside, was stereotaxically implanted 2 mm above the PPT (in relation to sterotaxic "0": anterior, 1.0 mm; lateral, 1.8 mm; and horizontal, 3.0 mm) as described previously (Datta 2002; Datta et al. 2002).
Intracerebral microinjections and experimental design
After the adaptation recording sessions, microinjection sessions began. During experimental sessions, animals were connected to the polygraphic recording system 15 min before the first microinjection into the PPT. The microinjection system consisted of a 32-gauge stainless steel injector cannula with a 26-gauge collar that extended 2.0 mm beyond the implanted guide tube. The collar was connected to a 1.0-µl motor-driven Hamilton microsyringe with PE 20 tubing. In this study, a double-microinjection protocol was adopted as described earlier (Datta 2002; Datta et al. 1993). Briefly, each microinjection session consisted of two injections in the same site with a 15-min interval between the first and second injections. While the animal was connected to the recording system, the stylett was removed, and a control vehicle-filled (100 nl volume of 0.9% saline) or any one of the two drug-filled (1.5 nmol in 100 nl, SpCAMPS or Baclofen) injectors were introduced through the guide tube for the first injection. One minute after the insertion of the injector cannulae, 100 nl of control saline or any one of the two drugs was microinjected over a 60-s period (Pump II Pico Plus, Harvard Apparatus, Holliston, MA). The cannula was gently withdrawn 2 min after the injection, and the stylett was reintroduced inside the guide tube. For the second injection, control saline or SpCAMPS was injected into the same site using the same injector system as described for the first injection. During the microinjections, the animals were free to move around the cage with the cannulae in place. Because of the extended tubing, the injections could be made without restraining mobility of the animal. Immediately after completion of the microinjection procedure, polygraphic variables were recorded continuously for 6 h (between 10:00 AM and 4:00 PM), when rats would normally be sleeping (Datta 2000). Each of these rats received a total of two microinjections (100 nl each) into the PPT (left or right side) in a single experimental recording session. None of the rats were used for more than one microinjection recording session.
The injection protocol was designed so that 28 rats were divided equally into four groups (n = 7 rats/group). The first group received saline + saline injections (control group) into the PPT. The second group received baclofen + saline injections (GABAB receptor activation group) into the PPT. The third group received baclofen + SpCAMPS injections (GABAB receptor + PKA activation group) into the PPT. The fourth group received SpCAMPS + saline injections (PKA activation group) into the PPT. At the end of experimental session and before perfusion, with the use of same injector used for saline or drugs, 100 nl of black ink was microinjected 1 mm dorsal to each injection site for localizing the injection sites as described earlier (Datta 2002; Datta et al. 2001a).
Determination of behavioral states and data analysis
For the purpose of determining possible effects on sleep and wakefulness, polygraphic data were captured on-line in a computer using "Gamma" software (Grass Product Group, Astro-Med, West Warwick, RI). From this captured data, three behavioral states were distinguished and scored visually using "Rodent Sleep Stager" software (Grass Product Group, Astro-Med) as described earlier (Datta 2002; Datta et al. 2004). The behavioral states of wakefulness (W), slow-wave sleep (SWS), and REM sleep were scored in successive 10-s epochs. The polygraphic measures provided the following dependent variables, which were quantified for each recording session: 1) percentage of recording time spent in W, SWS, and REM sleep; 2) latency to onset of the first episode of REM sleep after the onset of recordings; 3) total number of REM sleep episodes; and 4) mean duration of REM sleep episodes. The effects of the four different treatments (saline + saline; baclofen + saline; baclofen + SpCAMPS; SpCAMPS + saline) on the percentages of W, SWS, and REM sleep were statistically analyzed using a two-way ANOVA with time as a repeated-measure variable (6 levels corresponding to 6 1-h epochs after injections) and treatment as a between-group variable (4 levels corresponding to the 4 different treatment groups). After a two-way ANOVA, post hoc Scheffe F tests were done to determine the individual levels of significant difference between the control (saline + saline) and the three different drug treatment protocols at six individual data points. Individual post hoc tests were also done to compare between three different drug treatment protocols. The latency, number, and duration of REM sleep episodes were analyzed using a one-factor ANOVA followed by post hoc Scheffe F tests. Statistical analyses (2-way ANOVA, 1-factor ANOVA, and Scheffe F test) were performed with the use of StatView statistical software (Abacus Concepts, Berkeley, CA).
Histological localization of injection site
At the conclusion of the microinjection experiments, rats were deeply reanesthetized with pentobarbital sodium (60 mg/kg, ip) and perfused transcardially with heparinized cold phosphate buffer (0.1 M, pH 7.4) followed by 4% paraformaldehyde in 0.1 M phosphate buffer. The brains were removed and processed for NADPH-diaphorase staining and histological localization of injection sites as described earlier (Datta 2002; Datta et al. 2001a). This NADPH-diaphorase staining was done to identify the cholinergic cell compartment of the PPT (Bredt and Snyder 1992; Bredt et al. 1991; Datta 2002; Datta et al. 1997; Hope et al. 1991; Vincent et al. 1983).
|
|
RESULTS |
|---|
|
|
|
The changes in the percentage of time spent in W after microinjections are summarized in Fig. 3. Two-way ANOVA indicated a significant main effect of treatment (df = 3, F = 9.32, P < 0.001), time (df = 5, F = 19.24, P < 0.001), and a significant treatment x time interaction (df = 15, F = 5.62, P < 0.001) on the total percentage of time spent in W. The results of post hoc analysis (Scheffe F tests) on total percentage of time spent in W are presented in Fig. 3. Post hoc analysis indicated that the microinjections of baclofen + saline and baclofen + SpCAMPS reduced total percentages of W significantly (F = 44.40 and 17.89; P < 0.001) compared with the microinjections of saline + saline (control group), only during the first hour. During the second hour, baclofen + saline and baclofen + SpCAMPS microinjected groups total percentages of W were less compared with saline control microinjections, but this reduction did not reach significance. Next, the total percentages of W in the baclofen + SpCAMPS and SpCAMPS + saline microinjection groups were compared (Scheffe F test) with the baclofen + saline microinjection group. This test revealed that the total percentage of W in the baclofen + SpCAMPS group was significantly higher only in the first hour (F = 5.99; P < 0.01), but in the SpCAMPS + saline group, total percentages of wakefulness were significantly higher in the first (F = 35.04; P < 0.001) and second hour (F = 3.12; P < 0.05). Similar post hoc tests between SpCAMPS + baclofen and SpCAMPS + saline groups revealed that the total percentages of W in the SpCAMPS + saline group were significantly higher in the first (F = 12.15; P < 0.001) and second hour (F = 4.16; P < 0.05). These results show that the application of baclofen into the PPT causes reduction in the total percentage of W. These results also showed that the application of SpCAMPS into the baclofen microinjection site attenuates baclofen-induced W-reducing effect.
|
The changes in the percentage of time spent in SWS after microinjections into the PPT are summarized in Fig. 4. A two-way ANOVA indicated a significant main effect of treatment (df = 3, F = 32.57, P < 0.001), time (df = 5, F = 14.19, P < 0.001), and a significant treatment x time interaction (df = 15, F = 3.61, P < 0.001) for total percentage of time spent in SWS. The results of post hoc analysis (Scheffe F test) for the total percentage of time spent in SWS are presented in Fig. 4. Post hoc analysis indicated that, after microinjections of baclofen + saline, the total percentages of SWS were significantly increased during the first (F = 41.81; P < 0.001), second (F = 5.0; P < 0.01), and third (F = 11.12; P < 0.001) hours of the postinjection period compared with after control saline + saline microinjections. Similar comparisons revealed that, after baclofen + SpCAMPS microinjections, total percentage of SWS increased significantly (F = 9.25; P < 0.001) only during the first hour compared with after saline + saline microinjections. The next set of post hoc tests (Scheffe F test) compared total percentages of SWS in the baclofen + SpCAMPS and SpCAMPS + saline microinjection groups with the baclofen + saline microinjection group. This test revealed that the total percentages of SWS in the baclofen + SpCAMPS and SpCAMPS + saline groups were significantly less during the first (F = 11.78; P < 0.001 and F = 53.15; P < 0.001), second (F = 3.26; P < 0.05 and F = 6.84; P < 0.01), and third (F = 18.89; P < 0.001 and F = 6.11; P < 0.001, respectively) hours of the postinjection period. A similar post hoc test between the baclofen + SpCAMPS and SpCAMPS + saline groups revealed that the total percentages of SWS in the SpCAMPS + saline group were significantly less in the first (F = 14.89; P <0.001) hour. These results show that the application of baclofen into the PPT increases SWS. These results also show that the application of SpCAMPS into the baclofen microinjection site attenuates baclofen-induced SWS increase.
|
The changes in the percentage of time spent in REM sleep after microinjections into the PPT are summarized in Fig. 5. A two-way ANOVA indicated a significant main effect of treatment (df = 3, F = 75.94, P < 0.001), time (df = 5, F = 44.92, P < 0.001), and treatment x time interaction (df = 15, F = 11.81, P < 0.001) on total percentage of time spent in REM sleep. The results of post hoc analysis (Scheffe F test) on total percentage of time spent in REM sleep are presented in Fig. 5. Microinjections of baclofen + saline into the PPT suppressed REM sleep completely for the first 3 h of the postinjection period. During the fourth hour after injection, REM sleep began to reappear, but the total percentages of REM sleep were significantly less both during the fourth (F = 21.05, P < 0.001) and fifth (F = 3.82, P < 0.05) hours compared with their saline + saline control values. On the contrary, in the first postinjection hour, the total percentages of REM sleep were significantly higher in the baclofen + SpCAMPS (F = 17.72, P < 0.001) and SpCAMPS + saline (F = 26.5, P < 0.001) groups compared with after microinjections of the control saline + saline group. Similar comparisons after baclofen + saline microinjection revealed that the total percentages of REM sleep after microinjections of both baclofen + SpCAMPS and SpCAMPS + saline were significantly higher during postinjection hours 1–5. The total percentages of REM sleep were not significantly different between the baclofen + SpCAMPS and SpCAMPS + saline microinjection groups. These results indicate that the microinjection of baclofen into the PPT suppress REM sleep, and this baclofen-induced REM sleep–suppressing effect could be eliminated by the subsequent application of SpCAMPS.
|
|
|
|
DISCUSSION |
|---|
|
Neurotransmitter receptor activation–mediated excitation and inhibition of PPT cells are important processes for the regulation of REM sleep (Datta 1995). For the excitation process, pharmacological and single-cell recording studies have shown that the activation of PPT kainate type glutamate receptors induces REM sleep (Datta 2002; Datta and Siwek 2002; Datta et al. 2002). For the inhibition process, studies have shown inhibitory neurotransmitter GABA activates GABAB receptors and suppresses REM sleep through inhibition of PPT REM-ON cells (Datta et al. 2003; Ulloor et al. 2004). In this study, I showed that the local application of GABAB receptor selective agonist suppresses REM sleep. These results are in agreement with the idea that the GABAergic system in the PPT is involved in the regulation of REM sleep by inhibiting PPT cells. Other studies have consistently shown that the activation of PPT cells increases wakefulness and/or REM sleep (Datta 2002; Datta and Siwek 1997; Datta et al. 2001a,b, 2002; Garcia-Rill 1991; Garcia-Rill et al. 1990, 2001; Radulovacki et al. 2004). Thus the activation or inhibition of PPT cells correspondingly increases or decreases REM sleep. In addition to the suppression of REM sleep, our results showed that the activation of GABAB receptors in the PPT reduces the total percentages of wakefulness. This observation is also consistent with the observation of another study that has shown the intracerebroventricular application of GABAB receptor antagonist increases wakefulness and REM sleep in the rat (Gauthier et al. 1997). Anatomical studies demonstrating that the PPT receives GABAergic inputs from many parts of the brain, including the substantia nigra and local neurons, further support the suggestion that the GABAergic system could modulate the physiological acitvity of PPT cells as well as behavioral states of wakefulness and REM sleep. (Beckstead 1983; Carpenter et al. 1981; Jackson and Crossman 1981; Jia et al. 2003; Moon-Edley and Graybiel 1983; Reese et al. 1995; Scarnati and Florio 1997; Scarnati et al. 1988; Steininger et al. 1992). The possibility that endogenous GABAergic neurotransmission in the PPT may modulate PPT cell activity is also supported by the presence of different types of GABA receptors and GABAergic fibers in the PPT (Bowery et al. 1987; Chu et al. 1990; Kosaka et al. 1987; Mugnaini and Oertel 1985). Collectively, the results of this study and results of earlier studies discussed above provide conclusive evidence to support that the endogenous GABA released in the PPT regulates physiological REM sleep and wakefulness by activating GABAB receptors.
This study showed that the activation of PPT cAMP-PKA by local application of SpCAMPS, an activator of cAMP-PKA activation, increases REM sleep. This result suggests that the activation of PPT cAMP-PKA is involved in the generation of REM sleep. Because earlier studies have shown that the inhibition of AC (Datta and Prutzman 2005) and cAMP-PKA (Bandyopadhya et al. 2006) in the PPT suppresses REM sleep, it is reasonable to suggest that the cAMP-PKA intracellular signaling system in the PPT is critically involved in the regulation of PPT cell activity and REM sleep. Besides these studies, a number of other studies in behaving cats and rats have looked at the involvement of signal transduction pathways in the pontine reticular formation (PRF), another site known to be involved in the regulation of REM sleep (Capece and Lydic 1997; Marks and Birabil 2000; Shuman et al. 1995). These studies have indicated that the signal transduction pathway activated by muscarinic cholinergic receptors involves a pertussis toxin–sensitive G protein, AC, cAMP, and PKA. In the rat, this signal transduction pathway in the PRF is also shown to be involved in spontaneous REM sleep (Marks and Birabil 2000). Thus it is reasonable to conclude that, depending on the anatomical site and involved neurotransmitter receptors, activation of the intracellular cAMP-PKA signaling system is excited and/or inhibited for the regulation of REM sleep.
The results of this study also showed that the local activation of intracellular cAMP-PKA blocked PPT GABAB receptor activation–induced REM sleep suppression. It is known that the activation of GABAB receptors is capable of inhibiting AC (Couve et al. 2000; Kerr and Ong 1995; Mody et al. 1994; Robbins et al. 2001; Sivilotti and Nistri 1991; Takahashi et al. 1998; Thompson 1994), and inhibition of AC prevents activation of the cAMP-PKA signal transduction pathway (Gilman 1987; Marinissen and Gutkind 2001). Thus it is logical to suggest that the PPT GABAB receptor activation–mediated REM sleep suppression effect may have been caused by the inhibition of cAMP-PKA signal transduction pathway. Earlier studies have shown that the inhibition of both AC and cAMP-PKA in the PPT suppresses REM sleep (Bandyopadhya et al. 2006; Datta and Prutzman 2005).
The results of this study are particularly valuable given recent evidence from studies in both academic and industrial settings indicating that novel compounds designed to modify intracellular signaling molecules have promising therapeutic potential for the treatment of neurodegenerative disorders, endogenous depression, and other psychiatric disorders (Coyle and Duman 2003; Gould and Manji 2002; Gunawardena and Goldstein 2004; Paez-Pereda 2005; Tortora and Ciardiello 2002). Because the phenomenology and neurotransmitters involved in narcolepsy, cataplexy, hypnogogic hallucinations, depression, and other major psychiatric and neurological disorders are closely related to those of normal REM sleep (Garcia-Rill 1997; Garcia-Rill et al. 2003; Rye 1997), there may be a convergence of mechanisms at the level of the brain stem. Therefore the results of these experiments will be important in developing rational schematics of pharmacological therapies for these persistent and debilitating disorders.
I chose to study chronically implanted freely moving rats because this preparation provides the most physiological approach to a longitudinal analysis of the behavioral and electrographic events related to the wake-sleep cycle (Datta and Siwek 2002; Datta et al. 2002; Ulloor et al. 2004). After the adaptation period of each experimental condition, the rats showed regular values of wake and sleep stages. Thus the microinjections of a pharmacologically active selective signal transduction-altering activator that affected electrographic signs of wake-sleep patterns could be evaluated accurately (Capece and Lydic 1997; Marks and Birabil 2000). Moreover, understanding the role of the intracellular signal transduction pathway in a behaviorally active living organism is a vital step toward creating ways to converge functional biochemistry and integrative physiology. However, a major limitation of the microinjection method relates to the diversity in the neurochemical and functional nature of the neuronal population affected by the drug application. In this study, a GABAB receptor selective antagonist, baclofen, and a selective activator of cAMP-PKA, SpCAMPS, were microinjected into the PPT. I injected these drugs into the part of the PPT (pars compacta) where most cells are known to be cholinergic (Mesulam et al. 1983; Rye et al. 1987) and express REM-ON type of activity (Datta and Siwek 2002). Nonetheless, I acknowledge that if there are noncholinergic and REM-OFF cells located within the targeted site, they will also be affected by the application of these drugs. Another limitation of the microinjection method is the extent of diffusion of injected materials. In recent years, several laboratories, including our own, have improved this technique tremendously in many different ways. Recent microinjection studies have shown that a major advantage of the microinjection technique is its ability to stimulate a relatively circumscribed neuronal pool (Bandyopadhya et al. 2006; Capece and Lydic 1997; Datta et al. 2001a,b, 2003; Marks and Birabil 2000). This view is supported by biophysical studies of drug diffusion (Nicholson 1985), and distribution kinetics (Herz and Teschemacher 1971; Martin 1991). Diffusion data obtained from radiolabeled drug studies have shown that 30 min after brain microinjections of 500-nl volumes, 72% of the drug remained within a radius of 0.75 mm (Yaksh and Rudy 1978). In this study, the target area of the 100-nl drug solutions injected into the PPT (approximate size: length: 1.0; height: 1.0; and width: 0.8 mm), were well within the diffusion limit of this small volume. Moreover, in our recent microinjection mapping study in the PPT, it was shown that 100 nl of glutamate with drug concentrations similar to those used in this proposal were ineffective when injections were 0.5 mm away from the center of the PPT site (Datta 2002; Datta et al. 2001a,b). Additionally, using a similar microinjection technique, I showed that ibotenic microinjection-induced cell loss in the brain stem of rats was limited to a maximum radius of 0.35 mm. Other sleep-wake–related structures that are close to the PPT microinjection sites are the LDT and subcoeruleus nucleus. These two structures are 1 mm away from the PPT microinjection sites. Thus it is highly improbable that microinjected drugs used in this study (100 nl volume and 1.5 nmol dose) diffused into the LDT and subcoeruleus nucleus.
The results of this study also confirm a well-established fact that the activation of PPT is positively involved in the regulation of REM sleep (for reviews, see Datta 1995; McCarley 2004). Contrasting this view, a recent publication claimed that the total amount of REM sleep increases in the rat after PPT lesion (Lu et al. 2006). This study also claimed that lesioning the subcoeruleus alpha [labeled as sublaterodorsal nucleus (SLD)] suppressed REM sleep (Lu et al. 2006). However, numerous previous PPT lesion studies in both cats (Shouse and Siegel 1992; Webster and Jones 1988) and rats (Deurveilher and Hennevin 2001) have shown that the elimination PPT cholinergic cells suppressed physiological REM sleep. Moreover, one study has shown that rats with inbred cholinergic hyperfunction have excess REM sleep (Shiromani et al. 1988). More recently, it has also been shown that, in the animal model of Alzheimer's, impaired REM sleep is caused by the reduction of cholinergic cells in the PPT (Zhang et al. 2005). Collectively, these lesion studies provided much stronger and definitive evidence to indicate that the intact PPT cholinergic cells are critical for the generation of REM sleep.
Assuming PPT cholinergic cells are necessary for the generation of REM sleep, a careful analysis of previous studies reveals a potential oversight in the study of Lu et al. (2006). Stimulation studies have shown that the electrical and chemical stimulation of the PPT increases active wakefulness in rats and cats (Datta and Siwek 1997; Datta et al. 2001b; Garcia-Rill 1991; Garcia-Rill et al. 1987). On the other hand, using an excitotoxin lesion technique, studies have shown that the elimination of PPT cells suppresses motivational behaviors (Bechara and van der Kooy 1989, 1992; Olmstead and Franklin 1994); and consequently PPT lesioned rats spend more time in quiet wakefulness by reducing active wakefulness. Cortical EEG waves amplitudes and frequencies are very similar during quiet wakefulness and REM sleep (Datta and Hobson 2000). During quiet wakefulness, EMG sign of muscle tone in the rat is also very low, especially in PPT-lesioned rats. Thus it is possible that while identifying sleep-wake states, Lu et al. (2006) might have misidentified some quiet wake episodes as REM sleep episodes. It is also known that the lesion of nucleus subcoeruleus alpha suppresses REM sleep muscle atonia (Hendricks et al. 1982; Sakai 1980; Sanford et al. 2001; Shouse and Siegel 1992). Despite a reduction in REM sleep muscle atonia in these lesioned animals, the total amount of REM sleep is relatively unchanged. Similar to REM sleep muscle atonia, it has also been shown that the lesion of P-wave (one of the cardinal features of REM sleep) generator suppresses P-wave activity in the rat and cat during REM sleep (Datta and Hobson 1995; Mavanji et al. 2004). In these P-wave generator–lesioned rats and cats, the total amount of wakefulness, SWS, and REM sleep remains relatively unchanged. Therefore in these REM sleep sign generator–lesioned animals, identification of REM sleep is relatively more challenging than the identification of sleep-wake states in normal animals. It is likely that the SLD-lesioned rats of Lu et al. (2006) also exhibited some REM sleep episodes without muscle atonia. Therefore they might have failed to identify some of those dissociated REM sleep episodes. This could explain why the study of Lu et al. (2006) presents paradoxical results, such as reduced REM sleep accompanying an SLD lesion. Indeed, lesion of subcoeruleus nucleus (part of SLD) does not change total amount of REM sleep or wakefulness (Mavanji et al. 2004; Sanford et al. 1994).
In conclusion, this study showed that the inactivation of cAMP-PKA in the PPT is a critical step for the GABAB receptor activation–mediated regulation of REM sleep. The results also suggest that the activation of cAMP-PKA in the PPT is an important step to induce REM sleep. These data provide a novel perspective on the regulatory aspect of PPT cell activity in the regulation of REM sleep. These novel findings are critical for our complete understanding of the basic mechanisms in REM sleep regulation.
|
|
GRANTS |
|---|
|
|
|
ACKNOWLEDGMENTS |
|---|
|
|
|
FOOTNOTES |
|---|
Address for reprint requests and other correspondence: S. Datta, Sleep and Cognitive Neuroscience Lab., Dept. of Psychiatry, Boston Univ. School of Medicine, M-902, 715 Albany St., Boston, MA 02118 (E-mail: SUBIMAL{at}BU.EDU)
|
|
REFERENCES |
|---|
|
Bechara A, van der Kooy D. The tegmental pedunculopontine nucleus: a brainstem output of the limbic system critical for the conditioned place preference produced by morphine and amphetamine. J Neurosci 9: 3400–3409, 1989.[Abstract]
Bechara A, van der Kooy D. A single brain stem substrate mediates the motivational effects of both opiates and food in nondeprived rats but not in deprived rats. Behav Neurosci 106: 351–356, 1992.[CrossRef][Web of Science][Medline]
Beckstead RM. Long collateral branches of substantia nigra pars reticulata axons to the thalamus, superior colliculus and reticular formation in monkey and cat: multiple retrograde neuronal labeling with fluorescent dyes. Neuroscience 10: 767–779, 1983.[CrossRef][Web of Science][Medline]
Bowery NG. GABAB receptor pharmacology. Annu Rev Pharmacol Toxicol 33: 109–147, 1993.[Web of Science][Medline]
Bowery NG, Hudson AL, Price GW. GABA-A and GABAB receptor site distribution in the rat central nervous system. Neurosci 20: 365–383, 1987.[CrossRef][Web of Science][Medline]
Bredt DS, Glatt CE, Hwang PM, Fotuhi M, Dawson TM, Snyder SH. Nitric oxide synthase protein and mRNA are discretely localized in neuronal populations of the mammalian CNS together with NADPH diaphorase. Neuron 7: 615–624, 1991.[CrossRef][Web of Science][Medline]
Bredt DS, Snyder SH. Nitric oxide, a novel neuronal messenger. Neuron 8: 3–11, 1992.[CrossRef][Web of Science][Medline]
Capece ML, Lydic R. cAMP and protein kinase A modulate cholinergic rapid eye movement sleep generation. Am J Physiol (Regulatory Integrative Comp Physiol) 273: R1430–R1440, 1997.
Carpenter MB, Carleton SC, Keller JT, Conte P. Connections of the subthalamic nucleus in the monkey. Brain Res 224: 1–29, 1981.[CrossRef][Web of Science][Medline]
Chu DCM, Albin RL, Young AB, Penney JB. Distribution and kinetics of GABAB binding sites in rat central nervous system: a quantitative autoradiographic study. Neuroscience 34: 341–357, 1990.[CrossRef][Web of Science][Medline]
Cook SA, Welch SP, Lichtman AH, Martin BR. Evaluation of cAMP involvement in cannabinoid-induced antinociception. Life Sci 56: 2049–2056, 1995.[CrossRef][Web of Science][Medline]
Couve A, Moss SJ, Pangalos MN. GABAB receptors: a new paradigm in G protein signaling. Mol Cell Neurosci 16: 296–312, 2000.[CrossRef][Web of Science][Medline]
Coyle JT, Duman RS. Finding the intracellular signaling pathways affected by mood disorder treatments. Neuron 38: 157–160, 2003.[CrossRef][Web of Science][Medline]
Datta S. Neuronal activity in the peribrachial area: relationship to behavioral state control. Neurosci Biobehav Rev 19: 67–84, 1995.[CrossRef][Web of Science][Medline]
Datta S. Avoidance task training potentiates phasic pontine-wave density in the rat: a mechanism for sleep-dependent plasticity. J Neurosci 20: 8607–8613, 2000.
Datta S. Evidence that REM sleep is controlled by the activation of brainstem pedunculopontine tegmental kainate receptors. J Neurophysiol 87: 1790–1798, 2002.
Datta S, Hobson JA. Suppression of ponto-geniculo-occipital waves by neurotoxic lesions of pontine caudo-lateral peribrachial cells. Neuroscience 67: 703–712, 1995.[CrossRef][Web of Science][Medline]
Datta S, Hobson JA. The rat as an experimental model for sleep neurophysiology. Behav Neurosci 114: 1239–1244, 2000.[CrossRef][Web of Science][Medline]
Datta S, Mavanji V, Patterson EH, Ulloor J. Regulation of rapid eye movement sleep in the freely moving rat: local microinjection of serotonin, norepinephrine, and adenosine into the brainstem. Sleep 26: 513–520, 2003.[Web of Science][Medline]
Datta S, Mavanji V, Ulloor J, Patterson EH. Activation of phasic pontine-wave generator prevents rapid eye movement sleep deprivation-induced learning impairment in the rat: a mechanism for sleep-dependent plasticity. J Neurosci 24: 1416–1427, 2004.
Datta S, Patterson EH, Siwek DF. Endogenous and exogenous nitric oxide in the pedunculopontine tegmentum induces sleep. Synapse 27: 69–78, 1997.[CrossRef][Web of Science][Medline]
Datta S, Patterson EH, Spoley EE. Excitation of the pedunculopontine tegmental NMDA receptors induces wakefulness and cortical activation in the rat. J Neurosci Res 66: 109–116, 2001a.[CrossRef][Web of Science][Medline]
Datta S, Prutzman SL. Novel role of brain stem pedunculopontine tegmental adenylyl cyclase in the regulation of spontaneous REM sleep in the freely moving rat. J Neurophysiol 94: 1928–1937, 2005.
Datta S, Quattrochi JJ, Hobson JA. Effect of specific muscarinic M2 receptor antagonist on carbachol induced long-term REM sleep. Sleep 16: 8–14, 1993.[Web of Science][Medline]
Datta S, Siwek DF. Excitation of the brainstem pedunculopontine tegmentum cholinergic cells induces wakefulness and REM sleep. J Neurophysiol 77: 2975–2988, 1997.
Datta S, Siwek DF. Single cell activity patterns of pedunculopontine tegmentum neurons across the sleep-wake cycle in the freely moving rats. J Neurosci Res 70: 611–621, 2002.[CrossRef][Web of Science][Medline]
Datta S, Spoley EE, Mavanji VK, Patterson EH. A novel action of pedunculopontine tegmental kainate receptors: a mechanism of REM sleep generation in the rat. Neuroscience 114: 157–164, 2002.[CrossRef][Web of Science][Medline]
Datta S, Spoley EE, Patterson EH. Microinjection of glutamate into the pedunculopontine tegmentum induces REM sleep and wakefulness in the rat. Am J Physiol 280: R752–R759, 2001b.[Web of Science]
Deurveilher S, Hennevin E. Lesions of the pedunculopontine tegmental nucleus reduce paradoxical sleep (PS) propensity: evidence from a short-term PS deprivation study in rats. Eur J Neurosci 13: 1963–1976, 2001.[CrossRef][Web of Science][Medline]
El-Mansari M, Sakai K, Jouvet M. Unitary characteristics of presumptive cholinergic tegmental neurons during the sleep-waking cycle in freely moving cats. Exp Brain Res 76: 519–529, 1989.[CrossRef][Web of Science][Medline]
Enna SJ, Maggi A. Biochemical pharmacology of GABA-ergic agonists. Life Sci 24: 1727–1737, 1979.[CrossRef][Web of Science][Medline]
Falch E, Hedegaard A, Nielsen L, Jensen BR, Hjeds H, Krogsgaard-Larsen P. Comparative stereostructure-activity studies on GABA-A and GABAB receptor sites and GABA uptake using rat brain membrane preparations. J Neurochem 47: 898–903, 1986.[Web of Science][Medline]
Fromm GH, Shibuya T, Nakata M, Terrence CF. Effects of D-Baclofen and L-Baclofen on the trigeminal nucleus. Neuropharmacology 29: 249–254, 1990.[CrossRef][Web of Science][Medline]
Garcia-Rill E. The pedunculopontine nucleus. Prog Neurobiol 36: 363–389, 1991.[CrossRef][Web of Science][Medline]
Garcia-Rill E. Disorders of reticular activating system. Med Hypotheses 49: 379–387, 1997.[CrossRef][Web of Science][Medline]
Garcia-Rill E, Houser CR, Skinner RD, Smith W, Woodward DJ. Locomotion-inducing sites in the vicinity of the pedunculopontine nucleus. Brain Res Bull 18: 731–738, 1987.[CrossRef][Web of Science][Medline]
Garcia-Rill E, Kinjo N, Atsuta Y, Ishikawa Y, Webber M, Skinner RD. Posterior midbrain-induced locomotion. Brain Res Bull 24: 499–508, 1990.[CrossRef][Web of Science][Medline]
Garcia-Rill E, Kobayashi T, Good C. The developmental decrease in REM sleep. Thalamus and Related System 2: 115–131, 2003.
Garcia-Rill E, Skinner RD, Miyazato H, Homma Y. Pedunculopontine stimulation induces prolonged activation of pontine reticular neurons. Neuroscience 104: 455–465, 2001.[CrossRef][Web of Science][Medline]
Gauthier P, Arnaud C, Gottesmann C. Influence of a GABAB receptor antagonist on sleep-waking cycle in the rat. Brain Res 773: 8–14, 1997.[CrossRef][Web of Science][Medline]
Gilman AG. G proteins: transducers of receptor-generated signals. Ann Rev Biochem 56: 615–649, 1987.[CrossRef][Web of Science][Medline]
Gould TD, Manji HK. Signaling networks in the pathophysiology and treatment of mood disorders. J Psychosom Res 53: 687–697, 2002.[CrossRef][Web of Science][Medline]
Gunawardena S, Goldstein LS. Cargo-carrying motor vehicles on the neuronal highway: transport pathways and neurodegenerative disease. J Neurobiol 58: 258–271, 2004.[CrossRef][Web of Science][Medline]
Hendricks JC, Morrison AR, Mann GL. Different behaviors during paradoxical sleep without atonia depend on pontine lesion site. Brain Res 239: 81–105, 1982.[CrossRef][Web of Science][Medline]
Herz A, Teschemacher HJ. Activities and sites of antinociceptive action of morphine-like analgesics and kinetics of distribution following intravenous, intracerebral and intraventricular application. Adv Drug Delivery Res 6: 79–119, 1971.
Hill DR, Bowery NG. 3H-Baclofen and 3H-GABA bind to bicuculine insensitive GABAB sites in rat brain. Nature 290: 149–152, 1981.[CrossRef][Medline]
Hong YG, Henry JL. Effects of phaclofen and the enantiomers of Baclofen on cardiovascular responses to intrathecal administration of L- and D-Baclofen in the rat. Eur J Pharmacol 196: 267–275, 1991.[CrossRef][Web of Science][Medline]
Hope BT, Michael GJ, Knigge KM, Vincent SR. Neuronal NADPH diaphorase is a nitric oxide synthase. Proc Natl Acad Sci USA 88: 2811–2814, 1991.
Jackson A, Crossman AR. Basal ganglia and other afferent projections to the peribrachial region in the rat: a study using retrograde and anterograde transport of horseradish peroxidase. Neuroscience 6: 1537–1549, 1981.[CrossRef][Web of Science][Medline]
Jia H-G, Yamuy J, Sampogna S, Morales FR, Chase MH. Colocalization of 
-aminobutyric acid and acetylcholine neurons in the laterodorsal and pedunculopontine tegmental nuclei in the cat: a light and electron microscopic study. Brain Res 992: 205–219, 2003.[CrossRef][Web of Science][Medline]
Jones BE. Paradoxical REM sleep promoting and permitting neuronal networks. Arch Ital Biol 142: 379–396, 2004.[Web of Science][Medline]
Kerr DI, Ong J. GABAB receptors. Pharmacol Ther 67: 187–246, 1995.[CrossRef][Web of Science][Medline]
Kobayashi T, Good C, Biedermann J, Barnes C, Skinner RD, Garcia-Rill E. Developmental changes in pedunculopontine nucleus (PPN) neurons. J Neurophysiol 91: 1470–1481, 2004a.
Kobayashi T, Good C, Mamiya K, Skinner RD, Garcia-Rill E. Development of REM sleep drive and clinical implications. J Appl Physiol 96: 735–746, 2004b.
Kosaka T, Kosaka K, Hataguchi Y, Nagatsu I, Wu J, Ottersen OP, Storm-Mathisen J, Hama K. Catecholaminergic neurons containing GABA-like and/or glutamic acid decarboxylase-like immunoreactivities in various brain regions of the rat. Exp Brain Res 66: 191–210, 1987.[Web of Science][Medline]
Lai YY, Clements JR, Siegel JM. Glutamatergic and cholinergic projections to the pontine inhibitory area identified with horseradish peroxidase retrograde transport and immunohistochemistry. J Comp Neurol 336: 321–330, 1993.[CrossRef][Web of Science][Medline]
Lu J, Sherman D, Devor M, Saper CB. A putative flip-flop switch for control of REM sleep. Nature 441: 589–594, 2006.[CrossRef][Medline]
Marinissen MJ, Gutkind JS. G-protein coupled receptors and signaling networks: emerging paradigms. Trends Pharmacol Sci 22: 368–376, 2001.[CrossRef][Medline]
Marks GA, Birabil CG. Infusion of adenylyl cyclase inhibitor SQ22, 536 into the medial pontine reticular formation of rats enhances rapid eye movement sleep. Neuroscience 98: 311–315, 2000.[CrossRef][Web of Science][Medline]
Martin JH. Autoradiographic estimation of the extent of reversible inactivation produced by microinjection of lidocaine and muscimol in the rat. Neurosci Lett 127: 160–164, 1991.[CrossRef][Web of Science][Medline]
Mavanji V, Ulloor J, Saha S, Datta S. Neurotoxic lesions of phasic pontine-wave generator cells impair retention of 2-way active avoidance memory. Sleep 27: 1282–1292, 2004.[Web of Science][Medline]
McCarley RW. Mechanisms and models of REM sleep control. Arch Ital de Biol 142: 429–467, 2004.
Mesulam M-M, Mufson EJ, Wainer BH, Levey AI. Central cholinergic pathways in the rat: an overview based on an alternative nomenclature (Ch1-Ch6). Neuroscience 10: 1185–1201, 1983.[CrossRef][Web of Science][Medline]
Misgeld U, Bijak M, Jarolimek W. A physiological role of GABAB receptors and the effects of Baclofen in the mammalian central nervous system. Prog Neurobiol 46: 423–462, 1995.[CrossRef][Web of Science][Medline]
Mody I, De Koninck Y, Otis TS, Soltesz I. Bridging the cleft at GABA synapses in the brain. Trends Neurosci 17: 517–525, 1994.[CrossRef][Web of Science][Medline]
Moon-Edley S, Graybiel AM. The afferent and efferent connections of the feline nucleus tegmenti pedunculopontinus, pars compacta. J Comp Neurol 217: 187–215, 1983.[CrossRef][Web of Science][Medline]
Mugnaini E, Oertel WH. An atlas of the distribution of GABAergic neurons and terminals in the rat CNS as revealed by GAD immunohistochemistry. GABA and Neuropeptides in the CNS, Part I. In: Handbook of Chemical Neuroanatomy, edited by Bjorklund A and Hokfelt T. Amsterdam: Elsevier, 1985, vol. 4, p. 436–622.
Nicholson C. Diffusion of an injected volume of a substance in brain tissue with arbitrary volume fraction and tortuosity. Brain Res 333: 325–329, 1985.[CrossRef][Web of Science][Medline]
Olmstead MC, Franklin KB. Lesions of the pedunculopontine tegmental nucleus abolish catalepsy and locomotor depression induced by morphine. Brain Res 31: 134–140, 1994.
Paez-Pereda M. New drug targets in the signaling pathways activated by antidepressants. Prog Neuropsychopharmacol Biol Psychiatry 29: 1010–1016, 2005.
Paredes R, Agmo A. Stereospecific actions of Baclofen on sociosexual behavior, locomotor activity and motor execution. Psychopharmacology 97: 358–364, 1989.[CrossRef][Medline]
Paxinos G, Watson C. The Rat Brain in Stereotaxic Coordinates. San Diego, CA: Academic Press, 1997.
Punch LJ, Self DW, Nestler EJ, Taylor JR. Opposite modulation of opiate withdrawal behaviors on microinjection of a protein kinase-A inhibitor versus activator into the locus coeruleus or periaqueductal gray. J Neurosci 17: 8520–8527, 1997.
Radulovacki M, Pavlovic S, Saponjic J, Carley DW. Modulation of reflex and sleep related apnea by pedunculopontine tegmental and intertrigeminal neurons. Resp Physiol Neurobiol 143: 293–306, 2004.[CrossRef]
Reese NB, Garcia-Rill E, Skinner RD. The pedunculopontine nucleus-auditory input, arousal and pathophysiology. Prog Neurobiol 47: 105–133, 1995.[CrossRef][Web of Science][Medline]
Robbins MJ, Calver AR, Filippov AK, Hirst WD, Russell RB, Wood MD, Nasir S, Couve A, Brown DA, Moss SJ, Pangalos MN. GABAB2 is essential for G-protein coupling of the GABAB receptor heterodimer. J Neurosci 21: 8043–8052, 2001.
Rye DB. Contributions of the pedunculopontine tegmental region to normal and altered REM sleep. Sleep 20: 757–788, 1997.[Web of Science][Medline]
Rye DB, Saper CB, Lee HJ, Wainer BH. Pedunculopontine tegmental nucleus of the rat: cytoarchitecture, cytochemistry, and some extrapyramidal connections of the mesopontine tegmentum. J Comp Neurol 259: 483–528, 1987.[CrossRef][Web of Science][Medline]
Sakai K. Some anatomical and physiological properties of ponto-mesencephalic tegmental neurons with speciual reference to the PGO waves and postural atonia during paradoxical sleep in the cat. In: The Reticular Formation Revisited, edited by Hobson JA and Brazier MA. New York: Raven Press, 1980, p. 427–447.
Sanford LD, Cheng CS, Silvestri AJ, Tang X, Mann GL, Ross RJ, Morrison AR. Sleep and behavior in rats with pontine lesions producing REM without atonia. Sleep Res Online 4: 1–5, 2001.[Medline]
Sanford LD, Morrison AR, Mann GL, Harris JS, Yoo L, Ross RJ. Sleep patterning and behaviour in cats with pontine lesions creating REM without atonia. J Sleep Res 3: 233–240, 1994.[Web of Science][Medline]
Scarnati E, Florio T. The pedunculopontine nucleus and related structures. Adv Neurol 74: 97–110, 1997.[Web of Science][Medline]
Scarnati E, Hajdu F, Pacitti C, Tombol T. An EM and Golgi study on the connection between the nucleus tegmenti pedunculopontinus and the pars compacta of the substantia nigra in the rat. J Hirnforsch 29: 95–105, 1988.[Web of Science][Medline]
Shiromani PJ, Overstreet DL, Levy D, Goodrich CA, Campbell SS, Gillin JC. Increased REM sleep in rats selectively bred for cholinergic hyper activity. Neuropsychopharmacology 1: 127–133, 1988.[CrossRef][Web of Science][Medline]
Shouse MN, Siegel JM. Pontine regulation of REM sleep components in cats: integrity of the pedunculopontine tegmentum (PPT) is important for phasic events but unnecessary for atonia during REM sleep. Brain Res 571: 50–63, 1992.[CrossRef][Web of Science][Medline]
Shuman SL, Capece ML, Baghdoyan HA, Lydic R. Pertussis toxin-sensitive G proteins mediate carbachol-induced REM sleep and respiratory depression. Am J Physiol 269: R308–R317, 1995.[Web of Science][Medline]
Sivilotti L, Nistri A. GABA receptor mechanisms in the central nervous system. Prog Neurobiol 36: 35–92, 1991.[CrossRef][Web of Science][Medline]
Steininger TL, Rye DB, Wainer BH. Afferent projections to the cholinergic pedunculopontine tegmental nucleus and adjacent midbrain extrapyramidal area in the albino rat. I. Retrograde tracing studies. J Comp Neurol 321: 515–543, 1992.[CrossRef][Web of Science][Medline]
Steriade M, Datta S, Pare D, Oakson G, CurroDossi R. Neuronal activities in brain stem cholinergic nuclei related to tonic activation processes in thalamocortical systems. J Neurosci 10: 2541–2559, 1990.[Abstract]
Takahashi T, Kajikawa Y, Tsujimoto T. G-protein coupled modulation of presynaptic calcium currents and transmitter release by a GABAB receptor. J Neurosci 18: 3138–3146, 1998.
Thakkar MM, Strecker RE, McCarley RW. Behavioral state control through differential serotonergic inhibition in the mesopontine cholinergic nuclei: a simultaneous unit recording and microdialysis study. J Neurosci 18: 5490–5497, 1998.
Thompson SM. Modulation of inhibitory synaptic transmission in the hippocampus. Prog Neurobiol 42: 575–609, 1994.[CrossRef][Web of Science][Medline]
Tortora G, Ciardiello F. Protein kinase A as target for novel integrated strategies of cancer therapy. Ann NY Acad Sci 968: 139–147, 2002.[Web of Science][Medline]
Ulloor J, Mavanji V, Saha S, Siwek DF, Datta S. Spontaneous REM sleep is modulated by the activation of the pedunculopontine Tegmental GABAB receptors in the freely moving rat. J Neurophysiol 91: 1822–1831, 2004.
Vincent SR, Satoh K, Armstrong DM, Fibiger HC. NADPH-diaphorase: a selective histochemical marker for the cholinergic neurons of the pontine reticular formation. Neurosci Lett 43: 31–36, 1983.[CrossRef][Web of Science][Medline]
Wang L-Y, Salter MW, MacDonald JF. Regulation of kainate receptors by cAMP-dependent protein kinase and phosphatases. Science 253: 1132–1135, 1991.
Wang L-Y, Taverna FA, Huang X-P, MacDonald JF, Hampson DR. Phosphorylation and modulation of a kainate receptor (GluR6) by cAMP-dependent protein kainase. Science 259: 1173–1175, 1993.
Webster HH, Jones BE. Neurotoxic lesions of the dorsolateral pontomesencephalic tegmentum cholinergic area in the cat. II. Effects upon sleep-waking states. Brain Res 458: 285–302, 1988.[CrossRef][Web of Science][Medline]
Yaksh TL, Rudy TA. Narcotic analgesics: CNS sites and mechanisms of action as revealed by intracerebral injection techniques. Pain 4: 299–359, 1978.[CrossRef][Web of Science][Medline]
Zhang B, Veasey SC, Wood MA, Leng LZ, Kaminski C, Leight S, Abel T, Lee VMY, Trojanowski JQ. Impaired rapid eye movement sleep in the Tg2576 APP murine model of alzheimer's disease with injury to pedunculopontine cholinergic neurons. Am J Pathol 167: 1361–1369, 2005.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
TOP
ABSTRACT
INTRODUCTION
(n = 7), location of control saline + saline; 
(n = 7), location of baclofen + saline injection injector tips; 
(n = 7), baclofen + Sp-adenosine 3',5'-cyclic monophosphothioate triethylamine (SpCAMPS); 
(n = 7), location of SpCAMPS + saline injection injector tips. 4, trochlear nucleus; Aq, aqueduct; ATg, anterior tegmental nucleus; BIC, nucleus brachium inferior colliculus; CG, central gray; CnF, cuneiform nucleus; ctg, central tegmental tract; DR, dorsal raphe nucleus; dtg, dorsal tegmental bundle; IC, inferior colliculus; InCo, intercollicular nucleus; LL, lateral lemniscus; Me5, mesencephalic trigeminal tract/nucleus; MiTg, microcellular tegmental nucleus; Mlf, medial longitudinal fasciculus; Pa4, paratrochlear nucleus; PMR, paramedian raphe; PnO, pontine reticular nucleus, oral; PPT, pedunculopontine tegmental nucleus; RR, retrorubral nucleus; rs, tectospinal tract; scp, superior cerebellar peduncle; SPTg, subpeduncular tegmental nucleus; ts, tectospinal tract; VTg, ventral tegmental nucleus. Scale bar, 600 µm.
comparison with baclofen + saline, and #comparison with baclofen + SpCAMPS. 
