Food restriction during lactation suppresses Kiss1 mRNA expression and kisspeptin-stimulated LH release in rats.

Among the numerous physiological changes that accompany lactation is the suppression of the reproductive axis. The aim of this study was to investigate a possible role for the kisspeptin system in the restoration of the hypothalamic-pituitary-gonadal axis during late lactation in rats using a food restriction model that allows manipulation of the duration of lactational anovulation. Kiss1 mRNA expression and kisspeptin-immunoreactive cell counts were examined in both food-restricted dams and ad libitum (AL)-fed dams across late lactation when LH concentrations begin to increase. In the arcuate nucleus, Kiss1 mRNA expression and kisspeptin-positive cell counts were suppressed during late lactation. In the anteroventral periventricular (AVPV), day 15 food-restricted dams had significantly lower AVPV Kiss1 mRNA expression and a decreased LH response to exogenous kisspeptin compared with the AL-fed dams. Following 5 days of ad libitum food intake, these values were restored to levels similar to those in dams that had been fed ad libitum throughout lactation. In conclusion, this study shows that delayed restoration of the reproductive axis due to food restriction is associated with a decrease in kisspeptin sensitivity and low AVPV Kiss1 mRNA in late lactation.