Serotonin and MSH secretion: effect of parachlorophenylalanine on the pituitary cytology of the eel.
Parachlorophenylalanine (pCPA), an inhibitor of tryptophan hydroxylase which depletes brain serotonin in higher vertebrates, was injected into freshwater eels. After 4 or 6 injections (200 mg/kg/day) or 10 injections (100 and 140 mg/kg/day), the animals are paler, with a low melanophore index. In the pituitary gland, granules tend to accumulate in the basal part of the MSH cells and in the perinuclear area. Cells appear smaller with a decreased nuclear area (P less than 0.001). In the neurohypophysis, the amount of neurosecretory material is often reduced. Conversely, injections of 5-hydroxytryptophan induce a strong darkening, a result similar to that previously reported in some amphibian species and in one lacertilian species. These data substantiate the hypothesis of a stimulatory influence of 5-hydroxytryptamine on MSH release and possibly its synthesis in the eel and other lower vertebrates.
D006916:5-Hydroxytryptophan / Q000494:pharmacology; D000811:Anguilla / Q000502:physiology*; D000818:Animals; D010134:Fenclonine / Q000494:pharmacology*; D007030:Hypothalamo-Hypophyseal System / Q000378:metabolism; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000378:metabolism*; D008547:Melanophores / Q000187:drug effects; D010503:Periodic Acid-Schiff Reaction; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D012701:Serotonin / Q000502:physiology*
D012701:Serotonin; D009074:Melanocyte-Stimulating Hormones; D006916:5-Hydroxytryptophan; D010134:Fenclonine