Serotonin and dopamine as regulators of adenylate cyclase and relaxation in a smooth muscle of the mussel Mytilus edulis.

Serotonin and dopamine show similar dose-response relationships when they relax tonically contracted intact muscle fibres of the anterior byssus retractor muscle of Mytilus edulis. In saponin-treated muscle fibers, only serotonin or high doses of dopamine relax tonic contraction. In a membrane fraction, enriched in adenylate cyclase activity, serotonin and dopamine increase the rate of cAMP production. Serotonin is a far more potent activator of adenylate cyclase than dopamine.