Levels of prolactin, LH and FSH in the serum of intact and pelvic-neurectomized rats.

Abstract

Bilateral resection of the pelvic nerve in rats prior to mating blocks pregnancy and pseudopregnancy by preventing sustained luteal function. Intact and pelvic-neurectomized (PN) females were guillotined between 0300 and 0700 hr on the AM of vaginal cornification. Subgroups included unmated animals and animals sacrificed 20 min, 8 hr, 24 hr and 48 hr after mating. Intact males were also sacrificed 20 min after mating and without mating. Changes in serum levels of prolactin, follicle stimulating hormone (FSH) and luteinizing hormone (LH) were measured by double antibody radioimmunoassay procedures. Serum levels of prolactin, LH and FSH were elevated significantly (p < 0.001) 20 min after mating in both intact and PN females, while none of the 3 hormones was increased in the serum of intact males 20 min after copulation. In intact females at 8 hr after mating, the mean prolactin serum level was increased markedly to 151 ng/ml serum, whereas in PN females the level of prolactin averaged only 26 ng/ml serum (p < 0.001). By 24 hr the level of prolactin had decreased in intact females to 49 ng/ml, which was still significantly higher (p <0.05) than the 19 ng/ml found in the serum of PN females. By 48 hr prolactin levels were not significantly different between intact and PN females (20 and 14 ng/ml, respectively, p > 0.05). Serum levels of FSH and LH were not different between intact and PN rats at the time intervals compared (p > 0.05). It is concluded that the elevation in serum FSH, LH and prolactin 20 min after mating in females is not associated with a neural stimulus of the pelvic nerve as these increases occurred in both intact and PN rats. Moreover, since luteal activation occurs in intact, but not PN, rats, the elevation in serum levels of these 3 hormones at 20 min post coitus is not important in initiation of corpora luteal function. In contrast, the marked increase in serum prolactin at 8–24 hr after mating in intact females may be of major importance in luteal activation. (Endocrinology88: 937, 1971)