Estrogen and Progesterone Affect Electrically Induced Release of Luteinizing Hormone and Prolactin in Macaques 1

Abstract

We studied the effects of quasiphysiological regimens of estradiol-17β (E) and progesterone (P) on luteinizing hormone (LH) and prolactin release induced by electrical stimulation (ES) of the mediobasal hypothalamus (MBH) in ovariectomized monkeys. Monkeys with electrodes implanted in the MBH were treated with Silastic implants containing no steroid, E, or E plus P at 6, 24, or 30 hr prior to ES of the MBH. The following combinations were tested: 2E implants for 24 hr, 2E plus P for 24 hr, 1E for 30 hr, 1E plus P for 30 hr, 1E for 30 hr plus P for 6 hr, 2E for 30 hr, 2E for 30 hr plus P for 6 hr, empty implants. Blood was collected immediately before, during, and after stimulation. The serum was assayed for E, P, LH, and prolactin. With empty implants, the mean serum E concentration was 14 ± 2 pg/ml. This rose to 116 ± 14 for one E implant and to 224 ± 2.3 for two. One P implant raised the mean serum P concentrations from 0.30 ± 0.03 to 3.08 ± 0.21 ng/ml. The effect of E on serum LH varied among regiments—either no significant effect or reduction before, during, and after ES. Progesterone treatment significantly elevated LH concentrations before, during, and after ES. Prior to ES, serum prolactin concentrations of controls and E-treated animals were not significantly different. During ES the pattern of prolactin release was related to E dose. After ES, estrogen significantly affected both the mean concentration and rate of decline of serum prolactin. Progesterone had no significant effect on prolactin concentrations. These data show that, in the presence of E, P can facilitate LH release under both basal conditions and during ES.