Further Evidence that Central Neurotensin Inhibits Pituitary Prolactin Secretion by Stimulating Dopamine Release from the Hypothalamus 1

Abstract

Abstract

Intracerebroventricular (icv) injection of neurotensin (NT) (2 μg/rat) suppressed prolactin (PRL) release induced by L-5-hydroxytryptophan (1 mg/100 g body wt, iv), prostaglandin E₂ (1 μg/rat, icv), and FK33-824 (10 μg/100 g body wt, iv), a Met⁵-enkephalin analog, in urethane-anesthetized or conscious rats. In contrast, NT did not suppress elevated plasma PRL levels sustained by a large dose of domperidone (10 μg/100 g body wt, iv), a peripheral dopamine antagonist. In in vitro experiments, NT (10^-5 M) stimulated dopamine release from perifused rat hypothalamic fragments. These results suggest that central NT inhibits PRL secretion by stimulating dopamine release from the hypothalamus into hypophysical portal blood in the rat.