Mechanism of action of Jameson's mamba venom on the superior cervical ganglion of cat

Abstract

Dendroaspis jamesoni snake venom administered intra-arterially into the superior cervical ganglion, inhibits contraction of the cat nictitating membrane to supramaximal electrical stimulation of preganglionic nerve, when given in large doses, and facilitates it if administered in small doses. The block is at the superior cervical ganglion. The venom did not block the contraction of nictitating membrane to intra-arterial injections of direct depolarizers of the ganglion (1,1-dimethyl-4-phenylpiperazinium, methacholine, potassium chloride) whereas it blocked the contraction of the nictitating membrane to indirect depolarizers of the ganglion (acetylcholine, carbachol) and electrical stimulation of the preganglionic nerve followed by injection of neostigmine intra-arterially during stimulation. Radioactive studies with 45Ca showed that the percentage of injected radioactivity in the first effluent blood sample (1 min) was greater in cats treated with venom (74%) than in control cats (35%). The venom blocks the process, probably involving calcium, concerned in the release of acetylcholine. The venom itself, as judged by chromatographic separation and guinea pig ileal testing, contains acetylcholine or an acetylcholine-like material