Abstract: Objective To study the role of cholinergic receptors and their subtypes involved in the effects of acetylcholine (ACh) on the electric discharge of pain-excited neurons (PEN) in caudate nucleus of rat brain. Methods Trains of the electric impulses were applied to the left sciatic nerve as noxious stimulus ,the electric activities of PEN in caudate nucleus were recorded by extracelluar recording method with glass microelectrode after intracerebroventricular (i. c. v.) injection of ACh and muscarinic1 (M1) ,muscarinic3 (M3), muscarinic4 (M4) receptor antagonists and nAch-receptor antagonist. Results (1) I.c.v injection of ACh (20μg/10μl) showed the inhibitory effect of discharge of the PEN, resulted in the net-increased value (NIV) of frequency of induced discharge of the PEN decreased and the latency of the PEN lengthened. (2) This inhibition could be blocked by nAch-receptor antagonist (tubocurare ,0.8μg/10μl) and M1 receptor antagonist (pirenzepine,10μg/10μl). (3) This inhibition could not be blocked by M3 receptor antagonist (4-DAMP,10μg/10μl) and M4 receptor antagonist（tropicamide, 10μg/10μl）. Conclusions The results suggested that it was maybe mediated mainly by nAch-receptor and M1 receptor that ACh produced the analgesic effects in caudate nucleus of rat brain.