Neural actions of luteinizing hormone and human chorionic gonadotropin.

Luteinizing hormone (LH) and its homologue, human chorionic gonadotropin (hCG), are able to elicit multiple effects in the central nervous system (CNS) through binding to their receptors. Specific receptors for LH/hCG have been identified in the hippocampus, dentate gyrus, hypothalamus, cortex, brain stem, area postrema, cerebellum, choroid plexus, ependymal cells, glial cells, neural retina, pituitary gland, and neuron processes of the spinal cord. Neurotropic effects of LH and hCG have been demonstrated in fetal rat brain, where the expression of LH/hCG receptors is developmentally regulated. Administration of hCG has been found to be beneficial in restoration of transected spinal cord function in rats. In adult rat brain, LH and hCG are involved in the feedback regulation of synthesis and secretion of gonadotropin-releasing hormone (GnRH) in the hypothalamus and LH in the pituitary gland. LH and hCG also induce several behavioral and other changes that are associated with the hippocampus, which contains the highest density of LH/hCG receptors. Many of the behavioral changes induced by hCG in rats parallel those in pregnant women. Some of these behavioral effects are correlated with changes of eicosanoid metabolism induced by LH and hCG in the brain. The LH/hCG receptors present in the choroid plexus, brain vessels, and perihypophyseal vascular complex may be involved in the modulation of transport of LH, hCG, and GnRH into the CNS. Thus, the CNS is one of the specific target tissues for LH and hCG, by which LH/hCG act as pleiotropic hormones that regulate several reproduction-related as well as reproduction-nonrelated functions in the CNS.