OXYTOCIN AND VASOPRESSIN BINDING-SITES IN THE HYPOTHALAMUS OF THE RAT- HISTOAUTORADIOGRAPHIC DETECTION

Localization of oxytocin and vasopressin binding sites has so far been studied in the rat brain by means of film autoradiographs. The availa bility of selective iodinated ligands with high specific activity allo wed us to develop the histoautoradiographical technique and to reinves tigate at the microscopic scale the distribution of these sites in the hypothalamus. Most oxytocin binding sites were localized in delimited nuclei, e.g., the medial preoptic, the ventromedial, the ventral prem ammillary, the supramammillary, and the medial mammillary nuclei. In a ddition, a weak diffuse specific labeling occurred in the medial preop tic and the anterior hypothalamic areas. The vasopressin binding sites (of the V1 a type) were detected in delimited nuclei, e.g., the supra chiasmatic, the stigmoid, and the arcuate nuclei, but they were also d iffusely distributed in the lateral hypothalamic and the dorsochiasmat ic areas. The locations of neurohypophysial peptides binding sites det ected by light microscopy are compared with those previously obtained by film autoradiography.