Glucocorticoid receptors in LHRH neurons.

Luteinizing hormone-releasing hormone (LHRH)-producing neurons constitute the final pathway for regulation of reproductive endocrine function by the central nervous system. Chronically elevated levels of glucocorticoids exert an inhibitory effect on reproductive function. Although this is thought to be mediated in part via modulation of classical transmitters and peptides which regulate LHRH synthesis and release, it is also possible that glucocorticoids may regulate LHRH neurons directly. We localized glucocorticoid receptors (GR) in LHRH neurons in the rat central nervous system using immunocytochemistry. In males and randomly cycling females 10-24% of LHRH neurons in the medial septum-diagonal bands of Broca, and preoptic regions colocalized nuclear GR. Ovariectomy increased the percentage of GR/LHRH neurons at the level of the organum vasculosum of the lamina terminalis to 34%, half of which showed both nuclear and cytoplasmic GR. Treatment with estradiol reversed this effect. We suggest that the actions of glucocorticoids on reproductive endocrine function are mediated partly through direct modulation of LHRH gene expression and/or release by activated GR. Moreover, GR in LHRH neurons may provide a mechanism by which the gonadal steroid progesterone can affect LHRH neurons directly, despite a lack of progesterone receptors in these neurons.