title: Uptake and release of [3H]-serotonin in photophores of the midshipman fish, Porichthys notatus.
abstract: A kinetic analysis of [3H]-5-HT uptake in the photocytes of the photophores of Porichthys notatus revealed a high affinity (Km: 1.71 X 10(-7] and low affinity component (Km: 1.10 X 10(-5) M). The high affinity uptake was sodium- and potassium-dependent but largely insensitive to temperatures between 0 and 20 C. Ouabain (5 X 10(-3) M) and dinitrophenol (10(-3) M) reduced uptake significantly. DMI, imipramine and fluoxetine, in that order of potency, greatly inhibited [3H]-5-HT uptake. Noradrenaline and adrenaline reduced uptake in a non-competitive manner, while dopamine, tryptophan, 5-hydroxytryptophan and Cypridina luciferin had little or not effect on uptake. Non-facilitated luminescent responses to electrical stimulation were accompanied by release of [3H]-5-HT accumulated in the photocytes. Facilitatory luminescence excitation consistently failed to induce the release of [3H]-5-HT. Electrical and adrenaline (10(-5) M) stimulation of photophores after [3H]-5-HT release has occurred, failed to elicit any additional luminescent response. The photophores were responsive to KCN (10(-3) M) under these conditions. The results indicate that a specific carrier-mediated transport system is responsible for photocytic [3H]-5-HT uptake, and that release of photocytic [3H]-5-HT is stringently regulated and followed by inhibition of luminescence excitability.
mesh_terms: D000818:Animals; D005399:Fishes / Q000378:metabolism*; D066298:In Vitro Techniques; D007700:Kinetics; D010646:Phentolamine / Q000494:pharmacology; D010786:Photoreceptor Cells / Q000187:drug effects / Q000378:metabolism*; D011433:Propranolol / Q000494:pharmacology; D012701:Serotonin / Q000378:metabolism* / Q000494:pharmacology; D012867:Skin / Q000378:metabolism; D014364:Tryptophan / Q000378:metabolism
chemical_list: D012701:Serotonin; D014364:Tryptophan; D011433:Propranolol; D010646:Phentolamine