ROLE OF ALPHA(1)-ADRENOCEPTERS AND ALPHA(2)-ADRENOCEPTORS OF THE LATERAL HYPOTHALAMIC AREA ON URINARY-EXCRETION CAUSED BY CENTRALLY ADMINISTERED ANGIOTENSIN-II

To determine whether central alpha(1) and alpha(2)-adrenergic mechanis ms are involved in urinary sodium and potassium excretion and urine vo lume induced by angiotensin II (ANGII), these renal parameters were me asured in volume-expanded Holtzman rats with cannulas implanted into l ateral ventricle (LV) and lateral hypothalamus (LH). The injection of ANGII into LV in rats with volume expansion reduced the sodium, potass ium and urine excretion in comparison to the control injections of iso tonic saline, whereas prazosin (alpha(1) antagonist) potentiated these effects. Clonidine (alpha(2) agonist) and yohimbine (alpha(2) antagon ist) injected into LH previous to injection of ANGII into LV also abol ished the inhibitory effect of ANGII. These results suggest that the d ischarge of central alpha-adrenergic receptors has dual inhibitory and excitatory effect on antinatriuretic, antikaliuretic and antidiuretic effect induced by central ANGII in volume-expanded rats.