DISTRIBUTION OF OXYTOCIN-BINDING AND VASOPRESSIN-BINDING SITES IN THERAT EXTENDED AMYGDALA - A HISTOAUTORADIOGRAPHIC STUDY

Radioligand receptor autoradiography has shown that oxytocin- and vaso pressin-binding sites exist in numerous rat brain regions, among which the amygdala and the bed nucleus of the stria terminalis (BST) are es pecially prominent. However, these descriptions did not take into acco unt the numerous subdivisions of the amygdala and the BST Thus, we hav e reinvestigated the distribution of these sites in the rat extended a mygdala, which is formed by a continuum of structures stretching from the BST to the centromedial amygdala, including pacts of the accumbens nucleus, substantia innominata, and transition areas between the amyg dala and the striatum. For this purpose, histoautoradiography was used to detect binding sites at the cellular level, and anatomical boundar ies were defined on the basis of acetylcholinesterase histochemistry a nd tyrosine-hydroxylase immunohistochemistry. Oxytocin- and vasopressi n-binding sites were detected in well-defined subdivisions of both med ial and central parts of the extended amygdala, but they almost never coexisted in the same region. Compared with previously reported distri butions, our reinvestigation describes novel oxytocin- and vasopressin -binding sites in the lateral and supracapsular BST, in the sublenticu lar extended amygdala, in the interstitial nucleus of the posterior li mb of the anterior commissure, in the marginal zone, in the central am ygdaloid nucleus, and in the anterior amygdaloid area. These results i ndicate that oxytocin- and vasopressin-binding sites represent an impo rtant feature of the extended amygdala and may participate in the larg e variety of functions that characterize this area, including reproduc tive and ingestive behaviors, conditioned fear and autonomic regulatio n. (C) 1997 Wiley-Liss, Inc.