| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
EDITORIAL FOCUS
). Notably, Cx 36 expression decreased from postnatal days 7 to 17 to adult, paralleling the known developmental decrease in REM sleep in rats (Jouvet-Mounier et al. 1970). Additional slice electrophysiological findings demonstrate that SubC neurons exhibited a characteristic signature of electrical synapses, "spikelets," spontaneously or in response to the cholinergic receptor agonist carbachol. The spikelets were abolished by carbenoxolone, an inhibitor of gap junctions. Additional studies are needed to directly confirm that pairs of SubC neurons electrically communicate with one another as found for their cousins in the adjacent noradrenergic nucleus locus coeruleus (Christie et al. 1989).
Electrical synapses are known to contribute to synchrony in CNS neuronal networks. The best-studied electrical synapses in the CNS are in the inferior olive, where the oscillatory properties of single neurons endow the system with important dynamics; however, it is the gap junctions that are needed for synchronized neuronal ensemble activity (Leznik and Llinas 2005). Phasic activation of a group of SubC neurons is known to generate prominent field potentials called ponto-geniculo-occipital (PGO) waves, or P-waves in the rat, that are a cardinal sign of REM sleep (Datta et al. 1998). The findings of Heister et al. provide novel and exciting new avenues for the understanding sleep-wake control as well as for the treatment of sleep and arousal disorders. For example, Cx36-dependent neuronal gap junctions in the cortex may modulate synchronization of gamma oscillations (Traub et al. 2001). Cells in the reticular nucleus of the thalamus are known to be electrically coupled and to be responsible for the induction of network oscillations during slow wave sleep (Landisman et al. 2002). The presence of electrical coupling in the SubC described by Heister et al. may participate in the induction of network oscillations during REM sleep, and this result also introduces the possibility that electrotonic coupling may be involved in the process of sleep-dependent memory processing by providing oscillatory physiological activation necessary for long-term neuronal plasticity and memory formation (Datta 2006). Taken together, these findings provide exciting new possibilities for the modulation of sleep and arousal states, attentional processes, and even learning and memory by agents that control gap junctions and electrical coupling. Moreover, the potential roles of gap junction-dependent aberrant network oscillations in such disorders as narcolepsy, restless legs syndrome and insomnia are yet to be explored, but these seminal studies certainly point the way.
1Department of Anatomy and Neurobiology, University of Tennessee Health Center, Memphis, Tennessee; and 2Department of Psychiatry and Behavioral Neuroscience, Boston University School of Medicine, Boston, Massachusetts
Address for reprints and other correspondence: M. Ennis, Dept. of Anatomy and Neurobiology, Univ of Tennessee Health Center, Memphis, TN (E-mail: mennis{at}utmen.edu)
REFERENCES
Christie MJ, Williams JT, North RA. Electrical coupling synchronizes subthreshold activity in locus coeruleus neurons in vitro from neonatal rats. J Neurosci 10: 3584–3589, 1989.
Datta S. Activation of phasic pontine-wave generator: a mechanism for sleep-dependent memory processing. Sleep Biol Rhythms 4: 16–26, 2006.[CrossRef]
Datta S, Siwek DF, Patterson EH, Cipolloni PB. Localization of pontine PGO wave generation sites and their anatomical projections in the rat. Synapse 30: 409–423, 1998.[CrossRef][ISI][Medline]
Heister DS, Hayar A, Charlesworth A, Yates C, Zhou Y-H, Garcia-Rill E. Evidence for electrical coupling in the subCoeruleus (SubC) nucleus. J Neurophysiol 97: 3142–3147, 2007.
Jouvet-Mounier D, Astic L, Lacote D. Ontogenesis of the states of sleep in rat, cat, and guinea pig during the first postnatal month. Dev Psychobiol 2: 216–239, 1970.[Medline]
Landisman CE, Long MA, Beierlein M, Deans MR, Paul DL, Connors BW. Electrical synapses in the thalamic reticular nucleus. J Neurosci 22: 1002–1009, 2002.
Leznik E, Llinas R. Role of gap junctions in synchronized neuronal oscillations in the inferior olive. J Neurophysiol 94: 2447–2456, 2005.
Rash JE, Yasumura T, Dudek FE, Nagy JI. Cell-specific expression of connexins and evidence of restricted gap junctional coupling between glial cells and between neurons. J Neurosci 21: 1983–2000, 2001.
Traub RD, Kopell N, Bibbig A, Buhl EH, LeBeau FEN, Whittington MA. Gap junctions between interneuron dendrites can enhance synchrony of gamma oscillations in distributed networks. J Neurosci 21: 9476–9486, 2001.
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Visit Other APS Journals Online |
