Serotonin and dopamine as neurotransmitters in mytilus: block of serotonin receptors by an organic mercurial.

The effects of mersalyl, bromo-LSD (BOL) and methysergide (UML) on the relaxation of catch by certain indole and catechol derivatives were studied in the anterior byssus retractor muscle of Mytilus. Mersalyl antagonized relaxation in response to serotonin whereas BOL and UML were less effective. Two other indole derivatives, ergotamine and gramine, were also blocked by mersalyl; BOL and UML antagonized relaxation in response to dopamine more effectively than did mersalyl.