Abstract: Xylazine induced sedation in mice was observed as a kind of inhibition of exploratory activity. The reversible cholinesterase inhibitor cui xing ning (0. 25～1.0 mg. kg^-1), the preeusor of acetylcholine, choline bromide (100～300 mg. kg^-1 ), and the M-receptor agonist arecoline ( 1.0～5.0 mg. kg^-1 ) were shown to significantly antagonize xylazine (5. 0 mg. kg^-1 ) induced sedation. While cui xing ning (0. 25 mg. kg^-1) shifted the dose-response curve of xylazine induced sedation to the right, hemicholinum-3 (3 μg icv ), which inhibits the synthesis of acetylcholine, shifted the dose-response curve to the left. These results suggest that the xylazine induced sedation may be partly due to a reduced central cholinergic function. Cui xing ning may have some value in the treatment of xylazine overdose and antagonize the anesthesia induced by anesthetics combined with xyiazine.