The role of hypothalamic biogenic amines in the "gonadostat theory of puberty" is being examined by: 1) characterizing the alterations that occur in hypothalamic biogenic amine content and turnover during normal sexual maturation in male and female rats; 2) determining the effect of gonadal secretion on these parameters by obtaining biogenic amine measurements in castrate animals of similar ages; and 3) testing the hypothesis that changing sensitivity of the hypothalamic-pituitary axis to the negative feedback effects of gonadal steroids is mediated through changes in hypothalamic neurotransmitter metabolism. Intact and castrate male and female rats are being sacrificed at various ages during sexual maturation. Other groups of male and female rats are being castrated and implanted with silastic capsules containing four increasing doses of testosterone and estradiol respectively. After 8 days, the animals are sacrificed. Serum is obtained for the determination of LH, FSH, estradiol and testosterone (by radioimmunoassay). Brains are being removed for measurement of norepinephrine and dopamine content and turnover. Turnover is being measured by the synthesis inhibition technique using alpha methyl-p-tyrosine. The biogenic amine measurements are being performed in four subdivisions of the hypothalamus: ventral anterior, dorsal anterior, medial basal and posterior. By this approach, the complex relationships between gonadal steroids, biogenic amines in specific hypothalamic areas and pituitary gonadotropin secretion during sexual maturation are being defined to gain insight into the role of these systems in the process of puberty.