Characterization and autoradiographic localization of LHRH receptors in the rat brain

Luteinizing-hormone-releasing hormone (LHRH) is distributed in several extrahypothalamic areas, suggesting that it might act as a neurotransmitter or neuromodulator in the central nervous system. This study was undertaken to characterize and localize LHRH receptors in the rat brain by using slide-mounted frozen sections. The radioligand used was an iodinated stable LHRH agonist, [D-Ser(TBU)6, des-Gly-NH2(10)]LHRH ethylamide. It was clearly established that LHRH receptors with characteristics similar to those of pituitary LHRH receptors were present in the brain. They were found in high concentrations in the dorsal hippocampus, amygdala, septum, and subiculum and in very low amounts in the hypothalamus. Generally, a good correlation could be observed between receptor distribution and immunohistologically localized LHRH. These results strongly suggest that LHRH has multiple sites of action in the rat brain and reinforce the hypothesis that the peptide could act as a neurotransmitter/neuromodulator in the central nervous system.