Degeneration of monoamine nerves in anterior byssus retractor muscle of Mytilus induced by 5,6-dihydroxytryptamine.

Preliminary ultrastructural studies on the effects of 5,6-Dihydroxytryptamine (5,6-DHT) on the anterior byssus retractor muscle (ABRM) of Mytilus show degeneration of 2 types of monoaminergic nerves after 10 days of drug treatment. One type contained large granular vesicles (560-1,680 A) possibly represent serotonergic and dopaminergic nerves, thought to innervate this muscle. Two other types of profiles seemed to be unaffected by the drug. One conforms to cholinergic nerves while the other has a predominance of large opaque vesicles (1,200-2,500 A). The significance of these findings is discussed in the light of recent observations on the neurotoxic effects of 5,6-DHT on vertebrate and molluscan nerves.