Brain Research, 420 (1987)375-379 375 Elsevier BRE 22486 Angiotensin receptor binding in human hypothalamus: autoradiographic localization M.J. McKinley 1, A.M. Allen 2, J. Clevers 1, G. Paxinos 3 and F.A.O. Mendelsohn 2 1Howard Florey Institute of Experimental Physiology and Medicine, University of Melbourne, Parkville, Vic. (Australia), 2Department of Medicine, University of Melbourne, Austin Hospital, Heidelberg, Vic. (Australia) and 3School of Psychology, University of New South Wales, Kensington, N.S. W. (Australia) (Accepted 9 June 1987) Key words: AngiotensinII binding; Human brain; Lamina terminalis; Receptor; Diencephalon Binding of 125I-[Sara,IleS]angiotensin II in the human hypothalamus was mapped by in vitro autoradiographycarried out on frozen sections of hypothalamus from two human brains. Regions showingthe greatest specificbinding of this radioligand were the organum vasculosum of the lamina terminalis, median preoptic nucleus, subfornicalorgan, median eminence, arcuate nucleus and paraventric- ular nucleus. These regions may be sites of angiotensin II receptors involvedin the regulation of blood pressure, fluid balance and pitu- itary hormone secretion. Investigations in several animal species suggest that the octapeptide angiotensin II (AII) is an impor- tant neuroactive agent in the brain. Physiological studies have entailed examination of the effects of both peripherally and centrally administered All or its antagonists, and the effects of ablation of partic- ular sites in the brain involved in AII action 3,1°'a3,23, while biochemical and immunocytochemical investi- gations have resulted in the identification of compo- nents of the renin-angiotensin system in the central nervous system (CNS) 4'5'12'18. The results support the view that circulating AII acting on receptors within circumventricular organs (CVOs), and All gener- ated in the brain, have a role in the regulation of arte- rial blood pressure, fluid and electrolyte balance and secretion of hormones from both the anterior and posterior pituitary gland 3,11A7,21,22,25. Recently, we 1, 14,a5 and others 6'8,9,24 have mapped putative receptor sites for AII in the brains of laboratory animals by in vitro autoradiography. However, there is no evi- dence regarding the possible receptor sites for AII in the human CNS and the aim of the present study was to map the distribution of binding of a radiolabelled analog of AII to the human diencephalon. This re- gion of the brain was selected because (a) it includes structures which consistently show high All receptor binding in animal species 6'8'14'15'24, and (b) this region has the highest concentration of immunoreactive All fibers in the human brain 24. Blocks of hypothalamic tissue were obtained 6 h after death from a 71-year-old male who died of bronchopneumonia and adenocarcinoma, and from a 67-year-old female who died of disseminated carci- noma of the breast and obstructive renal failure. There was no clinical or pathological evidence of in- volvement of the CNS in either case. The hypotha- lamic block was frozen by contact with dry-ice, em- bedded in OCT compound (Tissue-Tek, Miles Labs., Napperville, IL) and immersed in a liquid hexane/ dry-ice freezing bath at -80 °C. Serial sections were cut on a cryostat at -14 °C in the coronal plane and thaw mounted onto gelatin-coated slides. The sec- tions were dehydrated at reduced pressure in a dessi- cator at 4 °C for 24 h, then stored at -20 °C. Adja- cent or near-adjacent sections were stained with Cre- syl violet and Luxol fast blue. For autoradiography, the sections were preincu- bated for 15 min as previously described 14A5 in 10 ml Correspondence: M.J. McKinley, Howard Florey Institute, Universityof Melbourne, Parkville, Vic. 3052, Australia. 0006-8993/87/$03.50 © 1987Elsevier SciencePublishers B.V. (BiomedicalDivision)