Kisspeptin and Seasonality of Reproduction - Kisspeptin Signaling in Reproductive Biology - page 400

Chapter 19
Kisspeptin and Seasonality of Reproduction
Iain J. Clarke and Alain Caraty
Abstract Wild and domesticated species display seasonality in reproductive
function, controlled predominantly by photoperiod. Seasonal alterations in
breeding status are caused by changes in the secretion of gonadotropin-releasing
hormone (GnRH) that are mediated by upstream neuronal afferents that regulate
the GnRH cells. In particular, kisspeptin appears to play a major role in seasonal-
ity of reproduction, transducing the feedback effect of gonadal steroids as well as
having an independent (nonsteroid dependent) circannual rhythm. A substantial
body of data on this issue has been obtained from studies in sheep and hamsters
and this is reviewed here in detail. Kisspeptin function is upregulated during the
breeding season in sheep, stimulating reproductive function, but contradictory
data are found in Siberian and Syrian hamsters. The relative quiescence of kiss-
peptin cells in the nonbreeding season can be counteracted by administration of
the peptide, leading to activation of reproductive function. Although there is a
major role for melatonin in the transduction of photoperiod to the reproductive
system, kisspeptin cells do not appear to express the melatonin receptor, so the
means by which seasonality changes the level of kisspeptin activity remains
unknown.
I. J. Clarke ( * )
Department of Physiology, School of Biomedical Sciences, Monash University,
PO Box 13F , Clayton , VIC 3800 , Australia
e-mail: [e-mail]
A. Caraty
Unité Mixte de Recherche, Physiologie de la Reproduction et des Comportements,
Université de Tours/Haras Nationaux , Nouzilly , France