title: Increased dopaminergic inhibition of prolactin in the hypoprolactinaemic IPL nude rat.
abstract: In this study, aimed at investigating whether dopaminergic regulation of prolactin could be implicated in the hypoprolactinaemia observed in the IPL nude rat, dopaminergic inhibition of prolactin was suppressed using a catecholamine synthesis inhibitor alpha-methyltyrosine (MT) and a dopaminergic antagonist sulpiride. Adult male rats (IPL nude and normal) were injected through implanted atrial cannulae with either MT (250 mg/kg) or physiological saline (control). Rats were decapitated 2 h after the injection. Plasma prolactin levels, compared with basal values, increased by 15.6 +/- 1.9 (S.E.M.)- and 5.89 +/- 0.6-fold in IPL nude and normal rats respectively. This difference was highly significant. The pituitary prolactin content was decreased in both groups. In a second experiment, adult male IPL nude or normal rats were injected with either sulpiride (1 mg/kg) or saline and decapitated 2, 4, 8, 12, 14 and 24 h later. Plasma prolactin levels, compared with basal values, were increased in rats injected with sulpiride by 9.2 +/- 1.8 and 3.4 +/- 0.7-fold in IPL nude and normal rats respectively. The pituitary prolactin content was reduced more in IPL nude than in normal sulpiride-injected rats. These data suggest that prolactin secretion, as well as synthesis, is under an increased dopaminergic inhibition in the male IPL nude rat.
mesh_terms: D000818:Animals; D004298:Dopamine / Q000502:physiology*; D008297:Male; D008781:Methyltyrosines / Q000494:pharmacology; D010902:Pituitary Gland / Q000378:metabolism; D011388:Prolactin / Q000097:blood* / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D011922:Rats, Mutant Strains; D013469:Sulpiride / Q000494:pharmacology
chemical_list: D008781:Methyltyrosines; C022260:alpha-methyltyrosine methyl ester; D013469:Sulpiride; D011388:Prolactin; D004298:Dopamine