THE effect on sleep organization of carbachol microinjected into diffe
rent amygdaloid nuclei was analysed in 12 cats. Single carbachol doses
of 8 mu g in 0.50 mu l saline were delivered unilaterally or bilatera
lly into the central, basal, lateral or basolateral amygdaloid nucleus
. Carbachol administration into the central nucleus induced a prolonge
d (5 days) enhancement of both REM sleep and its preceding slow wave s
leep episodes with PGO waves (sommeil phasique a ondes lentes, SPHOL),
which was more pronounced following bilateral than unilateral carbach
ol administration. However. neither SPHOL nor REM sleep changes were p
roduced by administration of carbachol into the other amygdaloid nucle
i. We conclude that cholinergic activation of the central amygdaloid n
ucleus produces a long-term facilitation of REM sleep occurrence.