Lactation effect on the mRNAs expression of RFRP-3 and KiSS-1 in dorsomedial and arcuate nuclei of the rat hypothalamus

Arginine-phenylalanine-amide-related peptide-3 (RFRP-3) and kisspeptin are believed to be inhibitor and stimulator of gonadotropin releasing hormone (GnRH) secretion, respectively. The aim of the present study was to compare the effect of lactation on the expression of RFRP-3 mRNA in dorsomedial hypothalamic nucleus (DMH) and KiSS-1 mRNA in arcuate nucleus (ARC) of hypothalamus in lactating and non-lactating rats. Fourteen rats of the Sprague-Dawley strain were randomly allocated into three groups. The non-lactating rats (n=5) were separated from their pups immediately upon parturition. The lactating rats were allowed to suckle five pups for eight days (the period of increasing of lactation). Relative expressions of RFRP-3 and KiSS-1 mRNAs compared to the control group were determined in DMH and ARC of hypothalamus, respectively, by using real-time PCR. Mean of relative expression of RFRP-3 mRNA in DMH in the lactating group was higher than that of the non-lactating rats (P=0.001). Relative expression of KiSS-1 mRNA in ARC did not show any difference between the lactating and the non-lactating rats (P=0.4). Increase of RFRP-3 mRNA expression in DMH of hypothalamus during the increase of milk production in rat may be the inhibitory factor for GnRH secretion. Whereas, no change in KiSS-1 mRNA expression in the ARC of the same rats may indicate the lower activity of this nucleus in the expression of the gene in both groups postpartum.