ANGIOTENSIN-III MODULATES NORADRENALINE UPTAKE AND RELEASE IN THE RATHYPOTHALAMUS

1 Effects of angiotensin III (A III) on H-3-noradrenaline (H-3-NA) tot al, neuronal and non-neuronal uptake, H-3 intracellular distribution a nd release were studied in vitro in the rat hypothalamus. 2 A III (1 m u M) decreased total, neuronal and non-neuronal H-3-NA uptake when hyp othalamic slices were incubated with H-3-NA for 30 min. A III effects on neuronal and non-neuronal H-3-NA uptake were determined in the pres ence of 100 mu M hydrocortisone or 10 mu M cocaine hydrochloride, resp ectively. The effect of A III on total H-3-NA uptake was blocked by 10 mu M Ile(7) angiotensin III (Ile(7) A III), an antagonist at A III re ceptors. In contrast, 100 nM A III had no effect on H-3-NA uptake. 3 T he study of the H-3-NA uptake time course showed that 1 mu M AIII decr eased NA uptake at 1, 3, 7, 15 and 30 min incubation. 4 In hypothalami c slices preloaded with H-3-NA for 30 min, 1 mu M AIII increased the H -3 content in the granular pool and decreased it in the cytosolic pool . 5 Spontaneous H-3 release was also modified by 1 mu M AIII when hypo thalami were preloaded with H-3-NA for 30 min. A III increased the spo ntaneous output of H-3. This effect was receptor-mediated since the ef fect of A III on H-3 release was antagonized by Ile(7) A III. 6 The pr esent results suggest that the effects of A III on NA neurotransmissio n, may be involved in the regulation of central angiotensin effects su ch as blood pressure control, hydrosaline balance and dipsogenesis, th rough modulation of central sympathetic activity.