Both pregnancy and lactation are associated with
hyperphagia, and circulating
leptin levels are elevated during pregnancy but decreased during lactation in Brandt's voles, Lasiopodomys brandtii. Previous findings suggest that impaired
leptin sensitivity contributes to
hyperphagia during pregnancy. The present study aimed to examine whether the decreased circulating
leptin level and/or hypothalamic
leptin sensitivity contributed to the
hyperphagia during lactation in Brandt's voles. The serum
leptin level and
mRNA expression of the long form of the
leptin receptor (Ob-Rb), suppressor-of-cytokine-signalling-3 (SOCS-3),
neuropeptide Y (NPY),
agouti-related protein (AgRP),
pro-opiomelanocortin (
POMC) and
cocaine- and
amphetamine-regulated transcript (CART) in the hypothalamus were examined on dioestrous, day 5, day 17 of lactation and day 27 (1 week after weaning) in Brandt's voles. Compared with controls, hypothalamic Ob-Rb and SOCS-3
mRNA expression was not significantly changed during lactation. The serum
leptin level was significantly lower in lactating females than in the non-reproductive group. Hypothalamic NPY and AgRP
mRNA expression significantly increased whereas
POMC mRNA expression was significantly decreased during lactation compared with controls. However, there were no significant changes in hypothalamic CART
mRNA expression. Food intake was positively correlated with NPY and AgRP
mRNA expression but negatively correlated with
POMC mRNA expression during lactation. These data suggest that
hyperphagia during lactation was associated with low
leptin levels, but not impaired
leptin sensitivity, and that the hypothalamic
neuropeptides NPY, AgRP and
POMC are involved in mediating the role of
leptin in food intake regulation in lactating Brandt's voles.