CARBACHOL INHIBITS BASAL AND FORSKOLIN-EVOKED ADULT-RAT STRIATAL ACETYLCHOLINE-RELEASE

ACUTELY dissociated adult rat striatal cholinergic neurons labeled wit h [H-3]choline were used ina perifusion system muscarine regulation of basal and forskolin-stimulated fractional [H-3]acetylcholine ([H-3]AC h) efflux in the absence of synaptic modulation. Carbachol inhibited b asal (40% maximal inhibition; IC50 similar to 0.7 mu M) and forskolin- evoked release (75% inhibition; IC50 similar to 0.05 mu M) in a concen tration-dependent manner, and both carbachol actions were abolished wi th atropine. Thus, activation of striatal muscarinic cholinergic autor eceptors potently inhibits basal and adenylate cyclase-stimulated ACh release. Tonic inhibitory control of cholinergic activity by functiona l striatal circuitry apparently prevents detection of these important physiological interactions in slices or in situ.