Effects of drugs that modify brain monoamine concentrations on plasma gonadotropin and prolactin levels in the rat.

Abstract

DL-α-Methyltyrosine (α-MT), which blocks catecholamine biosynthesis, produced a dramatic rise in plasma prolactin within 30 min of ip injection in castrated rats and treatment with α-MT for 4 days resulted in continued high levels of plasma prolactin and an elevation of pituitary prolactin concentration and content. Plasma FSH and LH were not significantly altered by α-MT. Selective blockade of norepinephrine (NE) biosynthesis with diethyldithiocarbamate (DDC) failed to alter prolactin levels but did lower plasma LH. Blockade of serotonin biosynthesis with p-chlorophenylalanine (p-CPA) failed to modify plasma levels of any of the 3 pituitary hormones measured and did not alter the elevation in plasma prolactin produced by concomitant administration of α-MT. When L-dihydroxphenylalanine (L-DOPA) was administered to elevate brain catecholamines, it lowered plasma prolactin but failed to alter FSH and LH levels. This lowering of piolactin by L-DOPA still occurred if conversion of dopamine (DA) to NE was bloc...