[Angiotensin II and nigostriatal system (author's transl)]

The central renin-angiotensin system is implicated most importantly in the control of water balance, blood pressure and endocrine function (AVP and ACTH). Several central structures are sensitive to angiotensin II (A II), principally: the subfornical organ, the vascular organ of the lamina terminalis, the area postrema and the preoptic area. Furthermore, binding studies with radio-active ligands and also immunohistofluorescence have shown respectively the presence of A II receptors and immunoreactive material bound by A II antibodies in other central structures, and in particular parts of the motor system. In the present study, a double approach, both electrophysiological and biochemical, was used to investigate the possible role of the peptide A II in the neostriatum of the rat. 1 Microiontophoretic application of A II was shown to modify the spontaneous activity of some neurones (15/68) in the neostriatum. Generally, the action of A II was inhibitory and the inhibition was blocked by Sar1-Ileu8-A II, a specific A II antagonist. 2 Angiotensin II 10(-6) M; 10(-5) M; 5.10(-5) M) stimulated the spontaneous release of 3H-dopamine continuously synthetized from 3H-tyrosine in striatal slices of the rat. The A II-evoked release of 3H-dopamine was prevented when slices were superfused with a calcium-free medium containing EGTA. It was also suppressed in the presence of the specific antagonist Sar1-Ileu8-A II. 3 Kainic acid lesion of the intrastriatal cell bodies produced a moderate decrease of A II in the striatum (38%) whilst the activity of the converting enzyme decreased dramatically (-68%). These results suggest that there are angiotensin-containing nerve endings in the neostriatum, and that the cell bodies of such nerves are located outside this structure. Their functional role is discussed.