Thus, an age-related decline in the ovarian follicular pool is associated with alterations in the pattern of follicular development and steroidogenesis, with potential impacts upon neuroendocrine function and oocyte quality. In light of these previous observations, it is conceivable that there is a functional correlation between the dramatic effects of P4 implant treatments on the maintenance of regular estrous cyclicity and on the conservation of the ovarian follicular reserve during aging. buy ampicillin
Little is known regarding the factors that may regulate the rate at which primordial follicles are recruited from the resting pool for development. It has been reported that hy-pophysectomy delays the rate at which ovarian follicles are lost during aging, suggesting a role of gonadotropins or other hypophysial factors in regulating follicular recruitment. In the present study, chronically elevated circulating P4 levels in P4-treated rats prevented cyclic increases in both FSH and LH secretion, although basal levels of gonadotropins were similar to that seen during the es-trous cycle. In addition, elevated circulating P4 levels were associated with the absence of cyclic rises in ovarian E2, presumably resulting from inhibitory effects of P4 on FSH-induced aromatase activity or prevention of cyclic increases in FSH release during implant treatment. Under this hormonal environment, follicular recruitment was apparently decreased, such that at 8 mo of age the P4-implanted rats had a follicular reserve three times greater than that of cyclic control females. Further studies are required to determine whether the marked effects of P4-implant treatments on follicular recruitment are directly due to the effects of elevated P4, the absence of cyclic increases in E2 and gonadotropins, or some combination thereof.