Role of prolactin and gonadal steroids in regulation of oxytocin
mrna during lactation.
Ghosh, Rita, and Celia D. Sladek.
Department of Physiology and Biophysics, University of Health
Sciences/The Chicago Medical School, North Chicago, IL 60064
APStracts 2:0044E, 1995.
The role of suckling, prolactin, and gonadal steroids in regulating
hypothalamic oxytocin (OT) mRNA content during the first and second
week of lactation was evaluated. On Day 4 of lactation, OT mRNA
content decreased in rats removed from their litter for 24 hours
compared to suckled controls. Either suckling (in the absence of
prolactin release) or prolactin (in the absence of suckling)
maintained OT mRNA content at this stage of lactation. In contrast,
at Day 11 of lactation, OT mRNA content remained unchanged in rats
deprived of pups for 24 hours. Ovariectomy did not compromise the
ability of Day 11, non-suckled rats to maintain OT mRNA content,
however, the increased water intake, plasma prolactin, plasma
vasopressin (VP), plasma renin concentration, and hypothalamic VP
mRNA content at Day 11 compared to Day 4 suggests a role for fluid
balance in determining OT mRNA content during the second week of
lactation. Thus, at Day 4, suckling is a major determinant of OT mRNA
content both as a result of direct activation of neuronal afferents
to the OT neurons and as a result of stimulation of prolactin
release. This is in contrast to Day 11 when fluid balance may
predominate in regulation of OT mRNA.
Received 1 September 1994; accepted in final form 24 February
1995.
APS Manuscript Number E357-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 10 March 1995.