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1Institute of Neurophysiology and 2Center of Molecular Medicine Cologne, University of Cologne, Cologne, Germany
Submitted 10 November 2006; accepted in final form 13 March 2007
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ABSTRACT |
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INTRODUCTION |
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; McKeown et al. 2006; Remy and Beck 2006). Interestingly, only a restricted number of these channels has been directly associated with epileptic disorders in humans and animal models so far, including Cav2.1 and Cav3.2 (Khosravani and Zamponi 2006). Recently, however, it turned out that the Cav2.3 E/R-type VGCC also harbors a potential proictogenic/proepileptogenic capacity that has been underestimated for a long time (Tai et al. 2006; Weiergräber et al. 2006a,b). Being resistant to most other VGCC antagonists, such as dihydropyridines (DHPs), 
-conotoxin GVIA, -conotoxin MVIIC, and -agatoxin IVA (Catterall et al. 2005), Cav2.3 E/R-type VGCCs exhibit a significant sensitivity toward Ni2+ (IC50 = 30 µM) (Schneider et al. 1994; Tottene et al. 2000) and the tarantula toxin SNX-482 (IC50 = 15–30 nM) (Newcomb et al. 1998).
Recent findings in hippocampal CA1 neurons elucidated that R-type channels can trigger epileptiform activity by contributing to plateau potentials after cholinergic stimulation (Kuzmiski et al. 2005; Tai et al. 2006). Muscarinic activation by M1/M3-cholinergic receptors was shown to enhance both Cav2.3 and R-type currents (Bannister et al. 2004; Melliti et al. 2000; Meza et al. 1999), but not T-type Ca2+ currents in rat hippocampal CA1 pyramidal neurons after P/Q-, N-, and L-type Ca2+ currents were selectively blocked (Tai et al. 2006). This muscarinic stimulation (e.g., using carbachol) is capable of inducing plateau potentials on the cellular level by G
q/11 and protein kinase C (PKC) but also theta bursts in extracellular recordings from the CA1 region (Tai et al. 2006). The epileptogenic capacity of Cav2.3 in triggering hippocampal seizure activity is further supported by the observation that M1 receptor knockout mice exhibit decreased seizure susceptibility after pilocarpine administration (Hamilton et al. 1997).
Interestingly, R-type Ca2+ channels exhibit a complex functional modulation based on internal Ca2+ levels and PKC-mediated phosphorylation. At lower cytosolic Ca2+ concentrations, a positive feedback mechanism, which includes activation through PKC, slows down inactivation and speeds up recovery from short-term inactivation (Klöckner et al. 2004; Leroy et al. 2003). Also, the pattern of Cav2.3 splice variant distribution in different brain regions is important for neuronal mechanisms underlying ictogenesis, seizure propagation, but also neuroprotection (Weiergräber et al. 2006a). In concordance with these findings, recent electroencephalographic characterization of Cav2.3-inactivated mice exhibited no indications of spontaneous epileptiform graphoelements. In contrast, pentylenetetrazol (PTZ)-seizure susceptibility was reduced and seizure architecture exhibited appreciable alterations in Cav2.3–/– mice compared with controls, supporting a proconvulsive capacity of Cav2.3 (Weiergräber et al. 2006a,b).
Given its contribution to plateau potential generation in CA1 hippocampal neurons capable of triggering epileptiform activity, we investigated the role of Cav2.3 in hippocampal seizure susceptibility and seizure architecture by means of electroencephalography (EEG) and behavioral analysis in both Cav2.3+/+ and Cav2.3–/– mice using kainic acid (KA) and N-methyl-D-aspartate (NMDA). We further performed histological analysis to unravel differences in hippocampal excitotoxicity. Our results demonstrate that Cav2.3–/– mice exhibit a pronounced resistance to hippocampal seizures and reduced excitotoxicity.
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METHODS |
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Generation of the Cav2.3 null mutant, which was backcrossed into C57Bl/6, was previously described in detail (Pereverzev et al. 2002; Weiergräber et al. 2006a). Cav2.3-deficient and control mice (with identical genetic backgrounds) from both genders were used in this study. Mice were housed in makrolon cages type II and maintained on a conventional 12-h light/dark cycle with food and water available without restriction. All animal experimentation was approved by the local institutional committee on animal care.
Hippocampal seizure-susceptibility testing: experimental design
Kainic acid (KA) and NMDA (both from Sigma, Munich, Germany) were freshly dissolved in physiological 0.9% NaCl before injection. Each animal was isolated for 
30 min before administration of convulsants.
Kainic acid–induced hippocampal seizures
The non-NMDA receptor agonist KA was administered intraperitoneally (ip) to Cav2.3+/+ (n = 18; 24.0 ± 0.7 g; 16.1 ± 0.8 wk) and Cav2.3–/– mice (n = 18; 25.5 ± 1.1 g; 22.9 ± 1.5 wk) at a dose of 30 mg/kg. Genders were exactly balanced with nine 
and nine 
in each study group. After injection animals were immediately placed back into their home cage, observed, and videomonitored for 2 h. Administration of KA causes a well-characterized hippocampal seizure syndrome that was analyzed according to a slightly modified seizure score from Baran et al. 1994: stage 1, no behavioral change; stage 2, facial clonus; stage 3, forlimb clonus; stage 4, rearing; stage 5, falling; stage 6, status epilepticus; stage 7a, jumping, tonic seizure <30 s; stage 7b, jumping, tonic seizure 30–60 s; stage 8, maximum generalized seizure activity, respiratory arrest, and death.
NMDA-induced hippocampal seizures
Seizures were induced by ip administration of NMDA at a dose of 150 mg/kg. Twenty Cav2.3+/+ (21.7 ± 0.8 g; 18.1 ± 1.9 wk) and 20 Cav2.3–/– (23.4 ± 0.9 g; 16.4 ± 1.2 wk) mice were used in this study and videomonitored for 2 h after injection. Genders were again balanced with seven and 13 in each population. In NMDA-treated mice, seizures developed through a sequence of paroxysmal scratching, hypermotility and circling, tonic–clonic convulsions, and, occasionally, death. The following semiquantitative scale was used for the examination of seizure severity slightly modified according to Marganella et al. 2005: stage 0, no response; stage 1, excessive grooming and paroxysmal scratching; stage 2, mild hypermotility; stage 3, extensive hypermotility and circling; stage 4, forepaw clonus and tail hypertonus; stage 5, generalized tonic–clonic convulsions; stage 6, status epilepticus; stage 7, death.
Collecting data for seizure-susceptibility analysis
Latencies were calculated as the time from injection of KA and NMDA to the first observation of the individual seizure phase. If animals did not undergo a specific seizure phase during the observation period, it was assigned a latency of 120 min for both substances. In addition, the frequencies with which an animal entered the various phases during the observation period were also counted. Time points and frequencies were noted on-line and rechecked using mouse video recordings.
Telemetric surface and intrahippocampal EEG recordings
Both TA10ETA-F20 and TL11M2-F20-EET transmitters (DSI, St. Paul, MN) were used for electrocorticographic and deep intrahippocampal EEG recordings in Cav2.3+/+ and Cav2.3–/– mice. The telemetry system, implantation procedure, and postoperative treatment were previously described in detail (Weiergräber et al. 2005).
SURFACE ELECTRODE IMPLANTATION (ELECTROCORTICOGRAM, ECOG). Epidural leads were positioned at the border of primary to secondary motor cortex (M1/M2) at the following stereotaxic coordinates: (+)-lead, bregma +1 mm, lateral of bregma 1 mm (left hemisphere); (–)-lead, bregma +1 mm, lateral of bregma 1 mm (right hemisphere) and fixed at the neurocranium using dental cement.
INTRACEREBRAL ELECTRODE IMPLANTATION.
For deep intrahippocampal recordings targeting the CA1 region electrodes were positioned as follows: (+)-lead, bregma –2 mm, lateral of bregma 1.5 mm (left hemisphere), dorsoventral (depth) 1.3 mm; (–)-lead, bregma –2 mm, lateral of bregma 1.5 mm (right hemisphere); dorsoventral 1.3 mm. In total, nine Cav2.3+/+ (28.0 ± 0.8 g, 17.5 ± 1.7 wk, all ) and nine Cav2.3–/– mice (28.8 ± 1.2 g, 20.1 ± 1.6 wk, all ) were analyzed that did not belong to the behavioral study groups. After recovery (7–10 days post-implantation) animals were administered KA at 10 mg/kg ip (n = 3 for each genotype) and 30 mg/kg ip (n = 6 for each genotype) and EEGs recorded for 2 h. In addition, daily recordings (minimum 1 h) were carried out in controls for 1 wk after injection.
Brain histology and histochemistry
Brains from KA (30 mg/kg ip) treated Cav2.3+/+ (n = 3, all ) and Cav2.3–/– (n = 3, all ) mice were exstirpated 7 days post-injection and fixed in 4% formaldehyde. Hippocampal sections (bregma: –1.7 mm) were analyzed for KA-induced excitotoxic effects using standard hematoxylin-eosin (HE) and Nissl-staining.
Statistical analysis
To acquire and analyze EEG data, the Dataquest A.R.T. 3.1 software (DSI) was used. EEG recordings were obtained as outlined earlier. In addition long-term deep intrahippocampal EEG recordings (>24 h) were performed 7–10 days post-surgery. EEG activity was sampled at 1,000 Hz with no filter cutoff. Absolute power spectrum density (PSD, mV2/Hz) was calculated from 5-min segments using the periodogram function (FFT based with Hanning windowing method). Frequency ranges were defined as follows: sub-
(0–1 Hz), (1–4 Hz), 
(4–8 Hz), (8–12 Hz), 
(12–32 Hz), 
(32–50 Hz). All data were calculated and displayed as the means ± SE. Statistical comparison of categorical variables (e.g., occurrence of seizure stages, lethality) was performed using Fisher's exact probability test (two-tailed), whereas continuous variables (e.g., seizure latencies, frequencies) were analyzed using the parametric Student's t-test, considering P < 0.05 as significant.
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RESULTS |
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Analysis of Cav2.3+/+ and Cav2.3–/– mice after KA administration revealed a complex alteration in behavioral seizure architecture with Cav2.3-deficient animals exhibiting pronounced seizure resistance (Table 1). The most prominent observation is that a significantly higher number of control mice exhibit severe status epilepticus (56.3 vs. 0%; P = 0.0017) and maximum generalized seizure activity associated with death (50 vs. 0%; P = 0.0010) compared with Cav2.3-deficient animals. This is concomitant with a significant reduction in stage 6 and stage 8 frequency and increase in latency for controls (Table 1A). Furthermore, stage 5 latency was significantly increased but frequency nonsignificantly reduced in Cav2.3–/– mice. No difference was observed between the two genotypes for both generalized seizure stages (stages 7a and 7b) characterized by jumping and tonic events except an increase in stage 7a frequency in Cav2.3–/– mice. Interestingly, some parameters of lower seizure severity (e.g., stage 2 and 3 frequency) were significantly increased in Cav2.3–/– mice similar to results obtained previously (Weiergräber et al. 2006a). However, similar to our prior studies using PTZ and 4-AP, KA-induced seizure severity is clearly reduced in Cav2.3-deficient mice (Table 1A). In particular, results from stages 6 and 8 point to a functional role of Cav2.3 in seizure perturbation and generalization.
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), although not reaching level of significance. Hippocampal NMDA seizure susceptibility in Cav2.3-deficient and control mice
NMDA seizure analysis of 20 controls and 20 Cav2.3–/– mice revealed a tendency similar to that observed for KA. Again, Cav2.3–/– mice exhibited reduced seizure susceptibility, particularly to stages of higher seizure severity. The survival rate of Cav2.3-deficient mice was 90%, but only 60% in control animals not reaching the level of significance (P = 0.0648). In addition, occurrence of generalized tonic–clonic convulsions and status epilepticus are also reduced in Cav2.3–/– mice close to the level of significance (Table 1B). Latency data for stages 5–7 are also increased in knockouts, although not significantly. It is also worthwhile to note that lethality in female Cav2.3+/+ mice was higher compared with males (46.2 vs. 28.6%), although not significant (P = 0.6424).
Electrocorticogram (ECoG) and deep intracerebral EEG recordings after KA administration
Analysis of deep intrahippocampal long-term EEG recordings from the CA1 region of both Cav2.3+/+ and Cav2.3–/– mice did not reveal any spontaneous ictal-like discharges that are indicative of limbic seizure activity (Fig. 1, A and B). Because seizure-susceptibility studies (see above) were carried out at 30 mg/kg to obtain behavioral phenomena, subsequent EEG recordings were also performed at that dosage (Figs. 1, C–F and 2, A and B). Initially, pilot studies were carried out to validate that intrahippocampal EEG recordings can be reliably distinguished from cortical EEG activity after KA administration by simultaneous recordings from the CA1 and M1/M2 region using a TL11M2-F20-EET transmitter (Fig. 2B). Unlike PTZ-induced seizure activity (Weiergräber et al. 2006a), we did not observe any indications of altered KA-induced seizure architecture. Analysis of ictal episode duration in Cav2.3+/+ (7.1 ± 2.3 min, n = 6) and Cav2.3–/– mice (6.5 ± 1.6 min, P = 0.8174, n = 6) did not reveal any difference (Fig. 3A) and similar results were obtained for interictal phases (3.9 ± 0.4 vs. 2.5 ± 0.7 min, P = 0.0868, n = 6, Fig. 3B). As depicted in Fig. 2, A and B both controls and Cav2.3-deficient mice exhibit contiguous spike and spike-wave activity throughout the 2-h observation period. This epileptic activity is within the delta- and theta-wave range (1–8 Hz), as confirmed by power spectrum analysis. At 30 and 10 mg/kg KA, no major differences in hippocampal seizure activity could be detected between both genotypes (Figs. 2 and 3). PSD analysis of ictal episodes (30 s) did not reveal any differences between both genotypes (Fig. 3C). Although analysis of the entire 2-h EEG recording period after KA (30 mg/kg) administration revealed a more rapid onset of theta, delta, and particularly subdelta activity in controls compared with Cav2.3–/– mice (Fig. 3D), these differences did not reach the level of significance. In addition, latency to first onset of exacerbating EEG seizure activity did not differ significantly between Cav2.3+/+ and Cav2.3–/– mice (7.2 ± 1.6 vs. 7.0 ± 2.7 min; P = 0.9351) and no alteration in latencies to peak PSD values for the individual frequency ranges could be detected (Fig. 3E). Thus hippocampal EEG seizure activity does not vary between Cav2.3+/+ and Cav2.3–/– mice at 30 mg/kg KA. Even at 10 mg/kg mice from both genders appeared to be behaviorally normal, although exhibiting a hippocampal status (Fig. 2, C and D). Thus both dosages turned out to be far beyond hippocampal seizure threshold in either genotype.
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Kainic acid–induced hippocampal excitotoxicity in Cav2.3+/+ and Cav2.3–/– mice
To unravel the role of Cav2.3 in modulating excitotoxic cell death we performed histochemical analysis of brains derived from Cav2.3–/– and Cav2.3+/+ mice 1 wk after ip administration of KA (30 mg/kg). In rodents, peripheral injections of KA result in recurrent seizures and subsequent degeneration of selected populations of neurons within the hippocampus. EEG recordings for a 1-wk period after KA administration revealed that, although decreasing, hippocampal seizure activity still persists (Fig. 1, C–F). This leads to a time-dependent, hyperexcitability-mediated neuronal degeneration within the hippocampus, particularly CA3, paving the way for further excitotoxic damage. Both Nissl and HE staining exhibit prominent neuronal cell loss and neurodegeneration in the CA3 region of Cav2.3+/+ mice but not in Cav2.3-deficient animals (Fig. 4, A–D). In Cav2.3+/+ mice, only 11% of neurons within the stratum pyramidale (CA3) exhibit an intact morphology after Nissl or HE staining (Fig. 4C). However in Cav2.3–/– mice, 89 and 90% of neurons reveal an intact cell shape after Nissl and HE staining, respectively. In addition, the number of countable (intact and degenerating) cells is reduced by 13.4% in Cav2.3+/+ mice compared with Cav2.3–/– mice. Note also the fading appearance of condensed chromatin in Cav2.3+/+ CA3 pyramidal neurons compared with Cav2.3-deficient animals (Fig. 4C, two left panels vs. right panels). As hippocampal seizure activity emerged to be similar in both genotypes at 30 mg/kg, reduced excitotoxicity in Cav2.3–/– mice also points to an intriguing role of Cav2.3 in neuronal cell degeneration and apoptosis.
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DISCUSSION |
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; Weiergräber et al. 2006b). Most studies in the past focused on Cav2.1 and Cav3.2 VGCCs. However, recent findings indicate that the Cav2.3 E/R-type Ca2+ channel can also serve as a proictogenic factor. Within the CNS Cav2.3 is widely distributed and preferentially localized either presynaptically or homogeneously on the soma and dendrites depending on the cell type (Weiergräber et al. 2006b; Westenbroek et al. 1995). Presynaptically, only a smaller fraction of Cav2.3 is restricted to the active zone of the vesicle fusion machinery and thus involved in neurotransmission (Wu et al. 1999), whereas a larger fraction is localized more distant in the synapse responsible for synaptic plasticity, e.g., long-term potentiation (LTP) (Breustedt et al. 2003; Dietrich et al. 2003). The somatic and dendritic expression of Cav2.3 is highly organized in space and contributes to the genesis of electrical phenomena resembling epileptiform activity (Magee 2000; McCormick and Contreras 2001; Williams and Kauer 1997). In addition, Cav2.3 is capable of inducing plateau potentials that underlie ictiform burst activity in various neuronal cell types (Kuzmiski et al. 2005; Tai et al. 2006). Its functional contribution to afterdepolarizations, which are also involved in epileptiform bursting, was previously reported (Metz et al. 2005) but remains controversial (Yue et al. 2005). In addition, Cav2.3 channels exhibit a complex regulation by G-protein–coupled signal transduction pathways, PKC, and internal Ca2+ levels, thus harboring remarkable but typical features of a seizure-susceptibility candidate (Weiergräber et al. 2006b).
We previously demonstrated that neither Cav2.3–/– mice nor control animals exhibit spontaneous epileptiform discharges in surface and deep intracerebral EEG recordings indicative of convulsive or nonconvulsive seizure activity. Interestingly, Cav2.3–/– mice turned out to be more resistant to PTZ-induced seizures, whereas 4-AP–induced seizure susceptibility remained unchanged (Weiergräber et al. 2006a). Based on recent electrophysiological studies in CA1 neurons pointing to a functional role of Cav2.3 in plateau potential generation in the hippocampus, we investigated the systemic effects of Cav2.3 ablation on hippocampal seizure activity using KA and NMDA. Behavioral analysis of 36 animals in total demonstrates that KA-induced seizure susceptibility (e.g., status epilepticus and lethality) is dramatically reduced in Cav2.3–/– versus control mice, supporting recent observations in CA1 neurons and validating the proconvulsive effect of Cav2.3 on the systemic, whole animal level. Similar findings were obtained for NMDA seizure susceptibility (40 animals in total), further strengthening the role of Cav2.3 in seizure initiation and generalization.
These results suggest that Cav2.3 acts solely as an electrophysiological regulator in triggering seizure initiation and propagation. However, studies by Suzuki et al. (2004) elucidated that Cav2.3 is likely to be involved in neuronal apoptotic processes related to excitotoxicity as well. Mutations in EFHC1, a novel interaction partner of the Cav2.3 VGCC, were reported to cause juvenile myoclonic epilepsy (JME) in humans. Normally, EFHC1 induces neuronal apoptosis by interaction with Cav2.3, whereas mutations in EFHC1 disrupt C-terminal binding and consequently result in lack of apoptosis and increased cell density, exhibiting hyperexcitable circuits as a result of altered neuronal connectivity (Suzuki et al. 2004). This functional role of Cav2.3 in neuronal degeneration is further supported by the observation that antiepileptic drugs (AEDs) known to block Cav2.3 (e.g., topiramate and lamotrigine) also exert strong neuroprotective effects (Caputi et al. 2001; Edmonds Jr et al. 2001; Hainsworth et al. 2003). Normal neuronal computation in the brain requires intense ongoing excitatory transmission. However, excessive excitatory activity results in neuronal damage and death, through a mechanism known as excitotoxicity (Ben Ari and Cossart 2000).
A major contributor to both hyperexcitability and excitotoxicity within the CNS is the glutamate system. Spreading of excessive glutamatergic neurotransmission eventually leads to sustained, paroxysmal network activity that can emerge into behaviorally observable symptoms. L-Glutamate is a neurotransmitter in a majority of excitatory synapses within the brain and acts on three classes of ionotropic receptors: NMDA, AMPA (-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid), and KA receptors. In excessive concentrations, glutamate has the potential to induce serious cell damage and even death to neurons, with NMDA and KA receptors located on neuronal cell bodies but also the pre- and postsynapse (Nicoll and Schmitz 2005). Kainic acid in particular is a well-characterized excitotoxin in the hippocampus and induces degeneration of cornu ammonis pyramidal neurons but also hyperexcitability in surviving CA neurons, provoking epileptiform activity and thereby serving as a model of complex partial seizure activity. Kainic acid–induced limbic seizure activity is initiated by paroxysmal discharges within the hippocampus and further spread to other limbic structures and finally to nonlimbic areas (Ben Ari 1985), resulting in various motor signs such as staring, head nodding, wet-dog shakes, recurrent limbic motor seizures, status epilepticus, and death. Both NMDA- and KA-receptor activation is associated with activation of VGCCs by prolonged depolarization and Ca2+-mediated excitotoxicity that might in part be responsible for neuronal cell death. However, the exact mechanisms yet have to be illuminated.
Interestingly, it was recently shown that KA receptors are expressed not only postsynaptically at the mossy fiber synapse, but also presynaptically together with Cav2.3 modulating neurotransmission in the CA3 region, probably related to the profound excitotoxic effects in this hippocampal region (Nicoll and Schmitz 2005). In addition, it turns out that more and more neuroprotectants and neurotransmitters that are upregulated after KA-induced seizures (Hunsberger et al. 2005) interact with or functionally modulate Cav2.3, e.g., hsp70 (Krieger et al. 2006) or neurokinin 1 (Meza et al. 2007).
Excitotoxic neurodegeneration clearly differs between the individual mouse strains. Studies by Schauwecker and Steward (1997) using 30 mg/kg KA revealed that 129/SvEMS and FVB/N mice exhibit excitotoxic cell death in the CA3 and CA1 regions of the hippocampus at lower doses. However, C57Bl/6 and BALB/c mice display neuronal cell death only at higher doses of KA in restricted areas (predominantly CA3), although the severity of seizures is comparable. Histochemical analysis of Cav2.3+/+ and Cav2.3–/– mice revealed clear indications of reduced excitotoxic cell death in the CA3 region of Cav2.3-deficient mice exhibiting a characteristic distribution pattern as reported previously (Schauwecker and Steward 1997). Because detailed analysis of hippocampal EEG seizure activity did not reveal differences between both genotypes at 30 mg/kg KA (Fig. 2, A and B), the explicit hippocampal invulnerability of Cav2.3–/– mice is likely to be a direct result of Cav2.3 ablation and not because of decreased limbic seizure intensity at that dosage. Given the complex distribution pattern of functionally divergent Cav2.3 splice variants in the CNS (Weiergräber et al. 2006) one can hypothesize that hyperexcitability and neuronal degeneration are mediated by different Cav2.3 splice entities in a direct or indirect way. Interestingly, the major, near-exclusive splice variant in hippocampus and neocortex corresponds to the Cav2.3c variant, which contains the exon 19 encoded insert 1 of the cytosolic II–III loop. This segment provides a novel Ca2+ and phorbolester sensitivity to Cav2.3c. Further, the II–III loop of Cav2.3 (with or without insert 1) represents the interaction site for the molecular chaperone hsp70 (Krieger et al. 2006). Hsp70 in particular was proved to be involved in neuroprotection. The investigation of disturbances of Cav2.3–hsp70 signaling may be an important target to understand neurodegeneration in epileptiform disorders.
Power spectrum density analysis did not reveal any differences in frequency distribution between both genotypes after KA administration (Fig. 3), particularly not in ictal discharges within the delta and theta range, which were reported to correlate with hippocampal atrophy and sclerosis in humans (Vossler et al. 1998).
This observation is of tremendous relevance because cell death associated with glutamate neurotoxicity contributes to the devastating secondary effects of epileptic disorders (Malva et al. 1998).
In summary, our recent findings point to a fascinating dual role of Cav2.3 in both ictogenesis and excitotoxicity. Electrophysiological studies on both the cellular and the systemic level of Cav2.3–/– mice strongly support a proictogenic capacity of the Cav2.3 VGCC. Moreover, the channel also mediates excitotoxic effects as first reported by Suzuki et al. (2004) in JME patients, now further validated by the observation of reduced KA excitotoxic susceptibility in Cav2.3–/– mice. Finally, Cav2.3 serves as a potent target for various AEDs, which exert neuroprotective effects. Clearly, these remarkable features bring the Cav2.3 VGCC into focus of pharmacotherapeutic research in epilepsy and neurodegeneration in the future.
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GRANTS |
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Address for reprint requests and other correspondence: M. Weiergräber, Institute of Neurophysiology and Center of Molecular Medicine Cologne (CMMC), Robert-Koch-Str. 39, D-50931 Cologne, Germany (E-mail: akp74{at}uni-koeln.de)
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ABSTRACT
INTRODUCTION
