Central noradrenergic neurones concentrate 3H-oestradiol.

Central catecholamines play an important part in the regulation of hormone secretion from the pituitary gland and in the mediation of male and female sexual behaviour. Noradrenaline has been shown to stimulate the release of luteinizing hormone (LH) probably by influencing the secretion of LH-releasing hormone (LHRH). The medial preoptic and hypothalamic areas, including the median eminence, contain noradrenaline-containing terminals which originate from discrete noradrenaline-containing cell groups in the lower brain stem. These cell groups have been identified in the pons and the medulla oblongata by histochemical methods and pharmacological experiments. Recent studies with antiserum to dopamine-beta-hydroxylase (DBH), the enzyme that converts dopamine to noradrenaline, provided evidence for the existence of noradrenergic cells. These include the locus coeruleus (group A6), a ventrally located more diffuse but continuous subcoeruleus group (group A5), a cell group located dorsal to the nucleus (n.) dorsalis motorius nervi vagi (group A2) and a cell group in or near the nucleus reticularis lateralis (group A1). Using the thaw-mount autoradiographic technique, oestradiol-concentrating neurones have been localized in many areas of the lower brain stem, including the locus coeruleus, n. tractus solitarii, n. dorsalis motorius nervi vagi, and reticular formation where catecholamine-containing neurones exist. We report here the simultaneous localization, in the same histological section, of 3H-oestradiol and the enzyme dopamine-beta-hydroxylase in neurones of the rat lower brain stem with a combined technique of thaw-mount autoradiography and immunohistochemistry, demonstrating that noradrenaline- or adrenaline-containing neurones are oestradiol target cells.