title: Plasma luteinizing hormone and prolactin levels and hypothalamic catecholamine synthesis in steroid-treated ovariectomized rats.
abstract: The effects of estrogen (E) and progesterone (P) on synthesis rates and endogenous levels of hypothalamic norepinephrine (NE) and dopamine (DA) were determined in individual ovariectomized (OVX) rats. 3H-tyrosine (3H-T) was injected intra-arterially and the rate of its incorporation into 3H-DA and 3H-NE was determined at 10, 15, 30, and 45 min. Steroid treatment for 2 days effectively decreased plasma LH levels and elevated plasma prolactin (Prl) levels while endogenous levels of NE and DA were not affected. NE synthesis was not affected by steroid treatment. A significant increase in DA synthesis was correlated with low plasma LH levels, suggesting that DA inhibits LH release. The elevated plasma Prl levels seen in steroid-treated rats were correlated with increased DA synthesis in the hypothalamus. This may indicate that elevated plasma Prl levels stimulate dopaminergic neurons in a short-loop negative feedback fashion.
mesh_terms: D000818:Animals; D002369:Castration; D002395:Catecholamines / Q000096:biosynthesis*; D004298:Dopamine / Q000096:biosynthesis / Q000502:physiology; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000037:antagonists & inhibitors / Q000097:blood*; D009638:Norepinephrine / Q000096:biosynthesis; D011374:Progesterone / Q000494:pharmacology*; D011388:Prolactin / Q000097:blood* / Q000502:physiology; D051381:Rats; D011954:Receptors, Dopamine / Q000502:physiology; D014443:Tyrosine / Q000378:metabolism
chemical_list: D002395:Catecholamines; D004967:Estrogens; D011954:Receptors, Dopamine; D014443:Tyrosine; D011374:Progesterone; D011388:Prolactin; D007986:Luteinizing Hormone; D004298:Dopamine; D009638:Norepinephrine