Effects of ovarian hormones on levels of luteinizing hormone in plasma and on serotonin concentrations in discrete brain nuclei.

Levels of serotonin were measureed in microdissected, individual brain nuclei in ovariectomized rats after treatment with ovarian hormones. Regions sampled included nuclei in the forebrain, rostral and medial hypothalamus, and midbrain tegmentum. Estradiol benzoate decreased levels of luteinizing hormone in plasma but did not affect serotonin levels in any region. Progesterone alone elevated serotonin content in the nucleus tractus diagonalis and ventral tegmental area. The combined estrogen plus progesterone regime produced a surge in plasma luteinizing hormone and also markedly elevated serotonin in the median eminence. These results may be of significance for ovarian hormonal regulation of gonadotropin secretion and reproductive behavior.