Lateral hypothalamic region excites the activity of vasopressin neurons in the supraoptic nucleus through subfornical organ neurons

Abstract

In urethane-anesthetized male rats, microinjection of angiotensin II into the lateral hypothalamic area excited the activity of about half ( N = 7) of subfornical organ neurons ( N = 15) antidromically identified as projecting to the hypothalamic supraoptic nucleus. Microinjection of angiotensin II also excited the activity of approximately one-quarter ( N = 8) of putative vasopressin-secreting neurons ( N = 28) in the hypothalamic supraoptic nucleus and these excitatory responses of putative vasopressin-secreting neurons were blocked ( N = 3) or attenuated ( N = 3) by pretreatment with the angiotensin II antagonist saralasin, but not by isotonic saline ( N = 2), in the subfornical organ.