The central theme of our Program Project continues to be elucidation of the mechanisms regulating the synthesis and secretion of FSH by the hypothalamic-pituitary axis and the gonadal actions of FSH. In this competitive renewal application we target three exciting areas of our central theme in projects designed (1) to elucidate the mechanisms which regulate hypothalamic production of GnRH leading to differential synthesis and release of FSH and LH by the pituitary at the times of the mid-cycle primary and secondary FSH surges in rats and of photic-dependent gonadal recovery in hamsters, (2) to elucidate the cellular mechanisms regulating inhibin production and actions, and (3) to investigate how cAMP orchestrates follicular development, resulting in the activation of select genes of immature granulosa cells and the inactivation of some of the same genes in mature granulosa cells. The six research projects and supporting cores which address these areas of FSH control and actions are: "Mechanisms Underlying Photoperiodic Regulation of Pituitary FSH and LH release", Dr. Fred Turek, PI; "Role of SF-1 and DAX-1 in Ovarian Function", Dr. J. Larry Jameson, PI; "Regulation of Ovarian Inhibin and Activin Subunit Gene Expression", Dr. Kelly E. Mayo, PI; Core B. "Molecular Technology Core", Dr. Kelly Mayo, Director, Core C. "Ligand Assay Core", Dr. Jon Levine, Director; Core D. "Inhibin and Activin Protein Production Core", Dr. Teresa Woodruff, Director. The issues addressed in this Program Project underlie the essence of the regulation of cyclicity, pregnancy,, and seasonal breeding. Our strengths include the expertise and enthusiasm of established reproductive scientists, our multi-disciplinary approach, overlapping co-investigators and the emphasis on collaborative endeavors with supporting cores and shared resources. By our united efforts we can optimize progress on each project to better understand the control and actions of FSH.