Abstract
Effects of dopamine, N-methyl-, ethyl and propyl-derivatives of dopamine, and alpha and beta-adrenoceptor stimulants on catch contraction of anterior byssus retractor muscle of Mytilus edulis were tested. The test drugs except the beta-adrenoceptor stimulants relaxed catch contraction. Dopamine was most active and substitution of amino group in dopamine with ethyl and propyl decreased activity considerably. The concentration-action curves of dopamine, its derivatives and norepinephrine shifted in parallel with application of haloperidol but were not influenced by the alpha and beta-adrenoceptor antagonists. These results suggest that relaxation of catch contraction by catecholamines is mediated through a dopamine receptor. This muscle is considered to be suitable for a study of the dopamine receptor.
