Two areas of research are being pursued by Dr. Plant. The first is directed at elucidating the neurobiological mechanisms that govern the ontogeny of pulsatile GnRH secretion throughout development in the monkey, and that therefore dictate the timing of the onset of puberty in this species. Currently, the notion that the pubertal reinitiation of pulsatile GnRH release involves an increase in GnRH gene expression and a structural and molecular reorganization of the afferent neural network governing release of this neuropeptide is being pursued. The finding that GnRH containing areas of the primate hypothalamus express embryonic neural cell adhesion molecule (PSA-NCAM) supports this idea. Attempts are being made to describe structural and molecular plasticity in the hypothalamus at puberty, and examine the consequence on sexual development of blocking hypothalamic remodeling at puberty. The second interest of this laboratory concerns the operation of the negative feedback loop governing spermatogenesis in the monkey. The molecular biology of inhibin's feedback action to inhibit FSHß gene expression and FSH secretion, the cell biology underlying the mechanism whereby FSH enhances the survival of germ cells indirectly via an action on the Sertoli cell, and the ontogeny of stem cells and undifferentiated spermatogonia in the monkey testis are also being studied.