GABA IN LOCUS-COERULEUS REGULATES SPONTANEOUS RAPID EYE-MOVEMENT SLEEP BY ACTING ON GABA(A) RECEPTORS IN FREELY MOVING RATS

The aminergic neurons in the locus coeruleus are known to cease firing during rapid eye movement sleep. Since electrical stimulation of locu s coeruleus reduced, while carbachol stimulation increased rapid eye m ovement sleep and gamma-aminobutyric acid (GABA) neurons as well as te rminals are present in the locus coeruleus, we hypothesized that GABA may be involved for cessation of locus coeruleus neuronal firing durin g rapid eye movement sleep. Under surgical anaesthesia male Wistar rat s (250-300 g) with bilateral guide cannulae targeting locus coeruleus were prepared for chronic sleep-wakefulness recording. Electroencephal ogram (EEG), electrooculogram (EGG), electromyogram (EMG) were recorde d in normal, after 250 nl saline and after picrotoxin (250 ng in 250 n l) injection bilaterally into the locus coeruleus. The results showed that mean duration per episode of rapid eye movement sleep was signifi cantly reduced, although its frequency of generation/h was not signifi cantly affected. This study suggests that GABA in locus coeruleus is i nvolved in tonic regulation of rapid eye movement sleep and the action is mediated through GABAA receptor. (C) 1997 Elsevier Science Ireland Ltd.