Treatment of castrated rats with gonadal steroids raises the lutenizing hormone releasing hormone (LHRH) stores in the hypothalmus. We are currently exploring various aspects of the mechanism of this central action of steroids. Primary emphasis is placed on identification of effective steroids, localization of the diencephalic site of action, the time course required for elevating LHRH stores, the possible involvement of catecholamines as neurotransmitters and the role of hypothalmic LHRH degrading enzymes. The second project deals with the study of several factors which may be involved in maintaining the observed circadian rhythmicities in serum levels of gondal steroids. Since these fluctuations were not correlated with serum gonadotropin levels we are investigating a direct interrelationship in the secretoy patterns of testicular and adrenal steroids. The possibility of modulating influences by the pineal, hypothalmus and prolactin are also being considered.