The anteroventral area of the rat brain third ventricle (AV3V) was stimulated by stereotaxically placed microinjections (1 µl) of hypertonic 1.5 mol/l NaCl and the responses of mean arterial pressure (MAP) and heart rate (HR) were recorded. Previous injection of terazosin or propranolol (5.0 µg) into AV3V, 15 min before 1.5 mol/l NaCl microinjection, did not alter the cardiovascular response pattern induced by 1.5 mol/l NaCl. Prior AV3V treatment with ketanserin (1.0 µg) significantly reduced (p < 0.01) the MAP and HR increase induced by 1.0 µl of 1.5 mol/l NaCl without changing basal cardiovascular parameters. Prior AV3V treatment with losartan (10.0 µg) significantly reduced (p < 0.01) the hypertension and tachycardia induced by hypertonic NaCl administration. Thus, AV3V serotonin and angiotensin II-sensitive neurons may exert an excitatory role on blood pressure and HR involved with the sympathetic discharge produced by hypertonic NaCl stimulation.

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