Dopaminergic regulation of gonadotropin levels and pulsatility in normal women.

This study was done to define the concentration of dopamine (DA) that inhibits gonadotropin secretion and to study the effect of DA D-2 receptor blockade during the infusions. Normal women received 5-hour infusions of either glucose (n = 14) or DA at rates of 0.04 (n = 6), 0.4 (n = 6), and 4.0  μ g/kg · minute (n = 9). After 3 hours, metoclopramide (MTC) was administered. Mean serum luteinizing hormone (LH) concentration declined during 0.4 ( P μ g/kg · minute ( P P  > 0.05) antagonized by MTC. Six women received DA (4.0  μ g/kg · minute) or glucose for 18 hours. After 17 hours, MTC was given. Blood samples were collected every 10 minutes during the last 8 hours. No significant effect on LH pulse frequency and pulse amplitude was observed ( P  > 0.05). A marked ( P