title: Stimulation of prolactin secretion by neuroleptics in rats with medial basal hypothalamic lesions.
abstract: The ability of dopamine receptor antagonists to stimulate prolactin release in rats with medial basal hypothalamic lesions was investigated. Starting levels of prolactin were elevated to approximately 400 ng/ml in animals in which the tuberoinfundibular dopaminergic neurons were completely destroyed by the lesion. In lesioned animals, chlorpromazine administration at doses of 0.1 and 5 mg/kg induced a further 2- to 3-fold significant increase in plasma prolactin levels. the incubation of anterior pituitaries from lesioned animals with 10(6) M chlorpromazine had no effect on prolactin secretion, thereby eliminating the possibility that chlorpromazine itself stimulates prolactin release from the anterior pituitary. A similar increase in plasma prolactin in lesioned rats was also observed with the potent dopamine antagonist d-butaclamol (1 mg/kg). The effect was stereospecific since the inactive isomer l-butaclamol did not produce any change in the circulating levels of prolactin. Pimozide, another dopaminergic antagonist, was ineffective in inducing a further increase in prolactin in lesioned rats when 0.63 mg/kg was used. However, at a 10-fold lower concentration (0.63 mg/kg), pimozide stimulated a significant increase in prolactin in lesioned rats. The involvement of an alpha-adrenergic mechanism was ruled out by the inability of phentolamine (2.5 mg/kg) to increase prolactin secretion. These data suggest that dopaminergic antagonists can further increase prolactin levels in medial basal hypothalamus-lesioned rats possibly by blocking the inhibitory action of dopamine from nonhypothalamic sources, or by releasing a substance which possesses prolactin-releasing activity.
mesh_terms: D000818:Animals; D014150:Antipsychotic Agents / Q000494:pharmacology*; D002069:Butaclamol / Q000494:pharmacology; D002746:Chlorpromazine / Q000494:pharmacology; D005260:Female; D007031:Hypothalamus / Q000502:physiology*; D007033:Hypothalamus, Middle / Q000502:physiology*; D010646:Phentolamine / Q000494:pharmacology; D010868:Pimozide / Q000494:pharmacology; D011388:Prolactin / Q000097:blood*; D051381:Rats
chemical_list: D014150:Antipsychotic Agents; D010868:Pimozide; D011388:Prolactin; D002069:Butaclamol; D002746:Chlorpromazine; D010646:Phentolamine