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Electrophysiological evidence that noradrenergic neurons of the rat locus coeruleus are tonically inhibited by GABA during sleep
Author(s) -
Gervasoni D.,
Darracq L.,
Fort P.,
Soulière F.,
Chouvet G.,
Luppi PH.
Publication year - 1998
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.1998.00106.x
Subject(s) - locus coeruleus , bicuculline , gabaergic , wakefulness , neuroscience , microdialysis , inhibitory postsynaptic potential , electrophysiology , tonic (physiology) , slice preparation , chemistry , premovement neuronal activity , slow wave sleep , efferent , antagonist , medicine , psychology , electroencephalography , receptor , central nervous system , afferent
Abstract It is well known that noradrenergic locus coeruleus (LC) neurons decrease their activity during slow wave sleep (SWS) and are virtually quiescent during paradoxical sleep (PS). It has been proposed that a GABAergic input could be directly responsible for this sleep‐dependent neuronal inactivation. To test this hypothesis, we used a new method combining polygraphic recordings, microiontophoresis and single‐unit extracellular recordings in unanaesthetized head‐restrained rats. We found that iontophoretic application of bicuculline, a specific GABA A ‐receptor antagonist, during PS and SWS restore a tonic firing in the LC noradrenergic neurons. We further observed that the application of bicuculline during wakefulness (W) induced an increase of the discharge rate. Of particular importance for the interpretation of these results, using the microdialysis technique, Nitz and Siegel ( Neuroscience 1997; 78 : 795) recently found an increase of the GABA release in the cat LC during SWS and PS as compared with waking values. Based on these and our results, we therefore propose that during W, the LC cells are under a GABAergic inhibitory tone which progressively increases at the entrance and during SWS and PS and is responsible for the inactivation of these neurons during these states.