Immunohistochemical localization of luteinizing hormone-releasing hormone (LH-RH) and somatostatin in the organum vasculosum of the lamina terminalis of the rat.

The role of the organum vasculosum of the lamina terminalis (OVLT) is almost completely unknown. In order to identify the content of the nervous structures present in this organ, we have localized by immunohistochemistry at both light and electron microscope levels two hypothalamic regulatory hormones: luteinizing hormone-releasing hormone (LH-RH) and somatostatin. It has been found that both LH-RH and somatostatin are localized in the nerve endings located at the proximity of the capillaries of the organum vasculosum. The two hormones are likely contained in different categories of nerve endings. The physiological importance of this organ still remains to be elucidated.