At 43 days of age, only 5 of 8 leptin-treated animals had shown VO, and 4 of 8 showed first estrus, whereas all ad lib-fed animals and no pair-fed animals had experienced these events. Thus, artificially elevated leptin levels may be insufficient to reverse the delay of pubertal onset that comes with food deprivation—ggugg thatleptin by itself cannot trigger the changes in GnRH secretion required to initiate puberty. buy ventolin inhalers
The ability of leptin to reverse the effects of reduced food intake on sexual maturation appears to reflect an action on the brain. In a severe food restriction paradigm, Gruaz et al. fed female rats at 36% of ad lib levels starting at postnatal Day 25, delaying the normal timing of VO. On Day 53, the animals received infusions of either saline or leptin (10 ^g/day) into the lateral ventricle. By Day 63, 8 of 9 animals receiving leptin had experienced VO, whereas all of the saline-treated animals remained in an arrested state. The authors also performed an experiment similar in design to that of Cheung et al., giving ventricular infusions of leptin (which reduced food intake to 63% of ad lib levels) starting at Day 29 and monitoring VO. As was the case with peripheral leptin injections, central delivery of leptin (at the dose used) was only partially able to rescue pubertal development, as by Day 38, 4 of 9 leptin-treated rats had showed VO compared with only 1 of 8 pair-fed animals.