Biology of Reproduction, Vol 29, 400-411, Copyright © 1983 by Society for the Study of Reproduction

ARTICLES

Role of pup age, estradiol-17 beta and pituitary responsiveness in the differences in the suckling-induced prolactin response during early and late lactation

M Selmanoff and C Selmanoff

The suckling-induced prolactin (Prl) response was studied in 10- and 20- day postpartum female rats. The response in 20-day postpartum mothers has a slower onset, has markedly reduced peak values and returns to baseline somewhat sooner than the response in 10-day postpartum mothers. The blunted response of late lactation was seen in mothers suckled for 30 min and was maintained over a longer interval in mothers continuously suckled for 120 min. This refractory phenomenon was not due to decreased suckling intensity provided by 20-day relative to 10- day-old pups. Pituitary gland Prl release in response to thyrotropin releasing hormone (TRH) and haloperidol challenges also did not distinguish 10- from 20-day postpartum mothers. Significantly higher estradiol-17 beta levels were found in 20-day compared with 10-day postpartum mothers, a finding which cannot account for the blunted response. Pup separation from 10-day postpartum mothers for 4, 24, 48 or 72 h did not produce a blunted response like that seen in late lactation. It is suggested that the hypothalamic mechanism mediating suckling-induced Prl release becomes refractory to the suckling stimulus during the preweaning period.

This article has been cited by other articles:

				L. M. Voloschin, M. G.P. Gallardo, and J. H. Tramezzani Suckling-Induced Serum Prolactin Levels Are Modified by Interference with Milk Ejection in Lactating Rats Biol Reprod, July 1, 1998; 59(1): 182 - 189. [Abstract] [Full Text]