Endocrinology, Vol 114, 618-623, Copyright © 1984 by Endocrine Society

ARTICLES

Relationship of prolactin release in lactating rats to milk ejection, sleep state, and ultrasonic vocalization by the pups

LM Voloschin and JH Tramezzani

PRL release, milk ejection, and electroencephalographic states of sleep were monitored in conscious, lactating Holtzman rats. Plasma PRL levels were low in rats separated from their litters, but they increased when pups were returned to the cage, attached to the nipples of the mother, and suckled. The pups emitted ultrasonic vocalizations upon their return to the cage and before their attachment to the nipples. Exposure of mothers to the vocalizations of pups, whereas nipple attachment was prevented, failed to increase PRL release. In confirmation of previous work, milk ejection did not occur until the suckled mother exhibited electroencephalographic signs of sleep, and milk ejection could be inhibited if sleep was prevented. In contrast, sleep was not a prerequisite for PRL release and sleep deprivation of suckled mothers could not inhibit release of PRL. In summary, suckling-induced release of PRL was followed by an increased incidence of sleep and then by milk ejection. It is hypothesized that the rise in plasma PRL induces the sleep necessary for the reflex release of oxytocin required for milk ejection.

This article has been cited by other articles:

				M. E. Freeman, B. Kanyicska, A. Lerant, and G. Nagy Prolactin: Structure, Function, and Regulation of Secretion Physiol Rev, October 1, 2000; 80(4): 1523 - 1631. [Abstract] [Full Text] [PDF]

				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]