Catecholamines and 5-hydroxytryptamine in photophores of Porichthys notatus. Radioenzymatic detection and radioautographic localization.

Radioenzymatic assays and light microscope radioautographic studies performed on photophores of Porichthys notatus demonstrated (1) significant amounts of catecholamines (dopamine, noradrenaline, adrenaline) and 5-hydroxytryptamine (serotonin) in these organs; (2) selective uptake and storage of [3H]noradrenaline ([3H]NA) by axon terminals innervating the photocytes, and (3) strong accumulation of [3H]5-hydroxytryptamine ([3H]5-HT) within the photocytes. Uptake and storage of [3H]NA in the nerve fibers were seemingly unaffected by the addition of ten-fold molar concentrations of unlabelled serotonin. Accumulation of [3H]5-HT by the photocytes was dose-dependent and diminished markedly in the presence of ten-fold molar concentrations of non-radioactive noradrenaline. Neither neuronal uptake of [3H]5-HT or [3H]A, nor photocytic accumulation of [3H]A were detectable under the conditions of the present experiments. This information should provide a framework for further investigations of the regulation of photophore luminescence by the biogenic amines.