EVIDENCE FOR THE EXCITATORY CHOLINERGIC INNERVATION IN THE RABBIT PORTAL-VEIN

We examined the possible existence of excitatory cholinergic innervati on in isolated rabbit portal vein. Longitudinal strips of the vein in the presence of both phenoxybenzamine, an alpha-adrenoceptor antagonis t, and N-G-nitro-L-arginine, an inhibitor of nitric oxide synthase, ex hibited a small contraction in response to transmural electrical stimu lation (ES). The contractile response to ES was augmented by physostig mine, an anticholinesterase agent, and inhibited by atropine. These fi ndings indicate the existence of an excitatory cholinergic innervation in addition to the known adrenergic and non-adrenergic, non-cholinerg ic innervations in the rabbit portal vein.