The effects of 5-hydroxytryptamine depletors and monoamine oxidase inhibitors on color changes of the fiddler crab, Uca Pugilator: Further evidence in support of the hypothesis that 5-hydroxytryptamine controls the release of red pigment-dispersing hormone

Abstract

1. The monoamine oxidase (MAO) inhibitors, iproniazid and nialamide, produced acceleration of the red pigment dispersion which occurs after intact crabs are transferred from a white to a black background but caused a decrease in the rate of red pigment concentration which occurs following transfer of intact crabs from a black to a white background.2. In contrast, the 5-HT depletors, p-chlorophenylalanine and reserpine, produced effects opposite to those observed with the MAO inhibitors on the rates of migration of the red chromatophoric pigment in response to background changes.3. These drugs do not have a direct effect on the red chromatophores. The drugs used did not produce either concentration or dispersion of the pigment in the red chromatophores of isolated legs.4. The results obtained with these drugs which are known to alter the level of 5-HT in nerve tissue are consistent with the hypothesis that 5-HT controls the release of red pigment-dispersing hormone.