The effects of temperature acclimation on monoamine metabolism.

Serotonin and dopamine content in the central nervous system of Mytilus edulis (Bivalvia) was assayed fluorometrically. Acclimating the animals for 2 to 4 days at a constant temperature higher than the environmental temperatures produced substantial increases in endogenous central nervous system serotonin and decreases in dopamine. p-Chlorophenylalanine and alpha-propyldopacetamide not only prevented this increase but reduced serotonin levels below those of unacclimated animals. Cycloheximide decreased the magnitude of the serotonin rise due to acclimation. Endogenous gill serotonin after acclimation also was higher. Gill filaments closest to the visceral ganglia were the first to increase. The study shows that hydroxylation of tryptophan is a temperature-sensitive step and axonal transport of tryptophan hydroxylase to the periphery accounts for terminal serotonin synthesis. A central pool of serotonin distinct from the peripheral pool was demonstrated. The study supports previous evidence of dopamine exerting a regulatory influence on serotonin metabolism in M. edulis.