Angiotensin II-binding sites in chicken brain and pituitary: autoradiographic localization

The distribution of binding sites for 125I-Val5-angiotensin II in the brain and the pituitary of control and dehydrated adult chickens of both sexes was determined by receptor autoradiography. Specific 125I-Val5-angiotensin II binding was mainly located in sensory areas, the limbic system and the hypothalamus including circumventricular organs and the nucleus paraventricularis. Since both the central angiotensin II system and the avian antidiuretic arginine-vasotocin system interact in osmoregulation, possible changes in angiotensin II binding intensities after dehydration were investigated in hypothalamic areas known to be involved in body-fluid homeostasis. There was an obvious increase in binding sites neither in areas where arginine-vasotocin synthesizing neurons were located, e.g. the nucleus paraventricularis and nucleus supraopticus, nor in other relevant areas for osmoregulation, e.g. the circumventricular organs of the hypothalamus. Furthermore, no sex difference in angiotensin II binding was observed.