The ability of the hypothalamus, pituitary, and ovaries to function as an integrated unit is essential for the reproductive success of every species. The primary aim of the proposed research is to arrive at a comprehensive picture of the development of the functional integration of the hypothalamus, pituitary, and ovaries. The domestic fowl (Gallus domesticus) will be used as the research animal, partly because the prolific reproductive capability of the hen makes it an excellent model with which to examine the development of reproduction, and partly because so little is known about the ontogeny of the hypothalami-pituitary-ovarian axis in any species, but particularly any avian species. There are 2 specific aims to the proposed research. Specific Aim #1 is to examine the development of the regulation of ovarian steroidogenesis by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Experiments are proposed that will utilize short-term incubations of dispersed ovarian cells and subsequent analysis of avarian steroid production by radioimmunoassay and high-performance liquid chromatography (HPLC). Specific Aim #2 is to investigate the development of the responsiveness of the hypothalamic-pituitary system to gonadal hormones. This will be done by measurement of plasma LH levels following In Vivo administration of estrogen and progesterone, and by examination of the In vitro production of LH by dispersed pituitary cells in response to LH-releasing hormone stimulation. A sensitive bioassay based on progesterone production by chicken granulosa cells will be used to measure LH. Fulfillment of these aims will contribute to our general knowledge of the interrelationship of the hypothalamus, pituitary, and ovaries during stages of sexual maturation and in the longer term will improve our understanding of the mechanisms underlying the regulation of female reproductive development and puberty. In addition, the proposed research will have value in terms of the comparative endocrinology of reproduction.