Increase in arcuate Kiss1 and Pdyn expressions may trigger the puberty onset in female rats

抄録

The timing of puberty onset is largely dependent on body weight rather than chronological age. To clarify the mechanism underlying the puberty onset, the present study examined the effects of food restriction and subsequent relief from the restriction on Kiss1 (kisspeptin gene), Tac3 (neurokinin B gene) and Pdyn (Dynorphine A gene) expressions in the arcuate nucleus (ARC) and puberty onset in rats, because the ARC kisspeptin neurons are considered to be responsible for GnRH/gonadotropin pulse generation. Female rats weaned on postnatal day (PND) 20 were ad lib-fed by the day when their body weight (BW) reached 75 g, and they were subjected to a restricted feeding to keep their BW at 70–80 g by PND 49. Then, half of the animals were subjected to ad libitum feeding on PDN 49 for 24 h and 48 h. The growth-restricted rats never showed pubertal sign during the experimental period. On the other hand, ad lib-fed animals showed catch-up BW growth and the pubertal sign. Animals that underwent catch-up growth showed apparent LH pulses on PND 50 and a LH surge and vaginal proestrus on PND 51, whereas growth-restricted rats showed suppressed LH release and vaginal diestrus on both days. The numbers of ARC Kiss1- and Pdyn-expressing cells were significantly higher in the ad lib-fed rats than growth-restricted controls on PNDs 50 and 51. No significant difference was found in the number of Tac3-expressing cells between groups. These results suggest that increases in kisspeptin and dynorphin A expressions in the ARC might be required for function of GnRH/gonadotropin pulse generator and that the increase may trigger the puberty onset via an increase in pulsatile GnRH/gonadotropin release in female rats.