Interestingly, the effect of neonatal TP treatment was clearly restricted to reproductive responses to SD. Neonatal TP strongly inhibited testicular growth in SD but had no effect on body weight. This suggests that SD may act independently on the reproductive axis and body weight, such that neonatal TP can enhance one effect but not the other. If so, then neonatal TP may act directly on photoresponsive elements of the reproductive axis. Alternatively, the mechanism by which neonatal TP enhances reproductive photoresponsiveness may be through a nonspecific enhancement of reproductive inhibition from any source (e.g., photoperiod, stress, or food). Our results do not allow us to distinguish between these possibilities. buy flovent inhaler
Neonatal androgens have powerful organizational effects on neural control of reproductive behavior and function. The enhancement of photoresponsiveness by exogenous androgen given neonatally is likely to be due to these organizational effects, but the mechanism is unknown. Neonatal androgens may enhance the sensitivity of the reproductive axis to feedback inhibition by androgens in adult life. F344 rats are known to be unusually sensitive to the effects of steroids and steroid negative feedback on the reproductive system. This suggests that the robust photoresponsiveness of F344 rats may be due to photoperiodic activation of a steroid negative feedback pathway acting on GnRH secretion.