Effect of pimozide on the cytology of the eel pituitary. I. Prolactin-secreting cells.
Pimozide, a specific blocker of dopaminergic receptors, was injected for 4 to 9 days in freshwater (FW) eels or eels acclimated to sea water (SW), for 10 to 30 days. The daily dose was 100 or 200 microgram/100 g. In FW, pimozide induces a nuclear hypertrophy in the prolactin (PRL) cells of eels; these elongated cells increase in height. The amount of erythrosinophilic granules in the cytoplasm, initially reduced, increases. Plasma electrolyte values are not modified: only the plasma sodium level slightly rises with the higher dose. In SW, PRL cells appear less active. After 10 days, this hypoactivity is not yet fully evident; pimozide stimulates PRL cells without affecting electrolyte values. After 1 month in SW, PRL cells are stimulated with pimozide and a slight regranulation may occasionally occur. The response in SW is never as marked as it is in FW; a high dose is not more effective than a low one. The higher dose significantly raises Na+, Ca2+ and Cl- plasma levels. These data suggest that prolactin synthesis and release increase with pimozide. They corroborate the hypothesis of a hypothalamic inhibitory control on PRL secretion mediated through dopaminergic fibers in the eel, but other factors may also be involved in this regulation in addition to the effect of salinity.
D000818:Animals; D002118:Calcium / Q000097:blood; D002712:Chlorides / Q000097:blood; D004524:Eels; D005618:Fresh Water; D008297:Male; D010868:Pimozide / Q000494:pharmacology*; D010902:Pituitary Gland / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D011388:Prolactin / Q000378:metabolism*; D012623:Seawater; D012964:Sodium / Q000097:blood; D014882:Water-Electrolyte Balance
D002712:Chlorides; D010868:Pimozide; D011388:Prolactin; D012964:Sodium; D002118:Calcium