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Chapter 10
Beyond the GnRH Axis: Kisspeptin
Regulation of the Oxytocin System
in Pregnancy and Lactation
Victoria Scott and Colin H. Brown
Abstract
Circulating oxytocin is critical for normal birth and lactation. Oxytocin
is synthesised by hypothalamic supraoptic and paraventricular neurons and is
released from the posterior pituitary gland into the circulation. Oxytocin secretion
depends on action potentials initiated at the cell body, and we have shown that
intravenous (IV) administration of kisspeptin-10 transiently increases the fi ring rate
of supraoptic nucleus oxytocin neurons in anaesthetised, non-pregnant, pregnant
and lactating rats. This peripheral effect is likely via vagal afferent input, because
disruption of vagal afferents prevented the excitation. In our initial studies,
intracerebroventricular (icv) administration of kisspeptin-10 did not alter the fi ring
rate of oxytocin neurons in non-pregnant rats. Remarkably, we have now gathered
unpublished observations showing that icv kisspeptin-10 transiently excites oxyto-
cin neurons in late pregnancy and during lactation, suggesting that a central kiss-
peptin excitation of oxytocin neurons emerges at the end of pregnancy, when
increased oxytocin secretion is required for delivery of the fetus and for milk let-
down after delivery.
Introduction
This chapter considers a newly emerging area of investigation in the kisspeptin
fi eld: the effects of kisspeptin on reproduction outside the hypothalamic-pituitary-
gonadal axis. When the endogenous ligand for the orphan GPR54 receptor (now
commonly known as Kiss1r in rodents and KISS1R in humans) was identifi ed as
kisspeptin, its possible role in modulating secretion of the hormone oxytocin was
V. Scott (
*
) • C. H. Brown
Centre for Neuroendocrinology and Department of Physiology,
University of Otago , PO Box 913 , Dunedin , 9054 , New Zealand
e-mail: victoria.scott@otago.ac.nz
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