Multiplicity of chemical mechanisms of regulation of muscle contractions in Lymnaea stagnalis L.

Abstract

Effects of acetylcholine, octopamine, and their antagonists, as well as of glutamic acid were studied on contractions of dorsal longitudinal muscle of the mollusc Lymnaea stagnalis L., evoked by electrical stimulation of n. cervicalis inferior. Acetylcholine and octopamine increased amplitude of contractions evoked by applications at concentrations about 10−8 M and decreased at concentrations higher than 10−7 M. Glutamic acid produced only inhibitory effect on the contraction amplitude, which appeared at concentrations beginning from 10−9 M and higher. The acetylcholine antagonists atropine and d-tubocurarine also decreased amplitude of evoked contractions. Their blocking effect rose with increase of their concentrations in the range from 10−9 M to 10−5 M. Specificity of the effect of the studied substances was established in experiments with a combined application of the transmitters and their antagonists. The obtained results indicate multiplicity of chemical mechanisms of regulation of contractions of the dorsal longitudinal muscle in L. stagnalis.