Functional evidence that acetylcholine release from Auerbach's plexus of guinea-pig ileum is modulated by alpha 2A-adrenoceptor subtype.

The effects of alpha 2-adrenoceptor ligands on electrically stimulated [3H]acetylcholine release from longitudinal muscle strips of guinea-pig ileum were examined. Xylazine or oxymetazoline reduced the release of [3H]acetylcholine in a concentration-dependent manner, both these actions being antagonized by idazoxan, CH 38083, or WB 4101. Prazosin, considered as an alpha 2B-adrenoceptor antagonist, failed to modify the inhibitory effects of xylazine or oxymetazoline. It is concluded that the alpha 2-adrenoceptors involved in the modulation of acetylcholine release from cholinergic axon terminals of guinea-pig ileum are of the alpha 2A subtype.