Differential effects of hypothalamic deafferentation upon luteinizing hormone-releasing hormone in the median eminence and organum vasculosum of the lamina terminalis.

Complete deafferentation of the medial basal hypothalamus (MBH) was performed in male rats to ascertain the location of the cell bodies of nerve terminals containing luteinizing hormone-releasing hormone (LH-RH) in the external layer of the median eminence and the organum vasculosum of the lamina terminalis (OVLT). Radioimmunoassayable LH-RH in the MBH decreased to one-fourth of the control value 10 days after complete deafferentation, whereas, no change was observed in an area coextensive with the OVLT. Immunohistochemical staining of LH-RH appeared less intense within the median eminence of deafferented animals but was normal in the OVLT. These results suggest that the cell bodies of neurons producing LH-RH found in terminals in the OVLT lie outside the MBH. The possible explanations for the decreased LH-RH content in the median eminence are discussed.