EFFECT OF A NONPEPTIDE ANGIOTENSIN RECEPTOR ANTAGONIST ON WATER-INTAKE CAUSED BY CENTRALLY ADMINISTERED CARBACHOL IN THE RAT

Angiotensin II (ANG II) administered centrally produces drinking by ac ting on subtype 1 ANG II (AT1) receptors, Carbachol, a cholinergic rec eptor agonist, also induces drinking behavior by a central action. In the present study we determined whether the response to carbachol also involves AT1 receptors. Male Holtzman rats (250-300 g) with stainless steel cannula implanted into the lateral ventricle (LV) were used. Wa ter intake after injection of 0.15 M NaCl (1.0 mu l) into the LV was 0 .2 +/- 0.01 ml/h (N = 8). The AT1 receptor antagonist DUP-753 (50 nmol /mu l) injected into the LV reduced water intake induced by ANG II (10 nmol/mu l) from 9.2 +/- 1.4 to 0.4 +/- 0.1 ml/h (N = 8), and water in take induced by carbachol (2 nmol/mu l) from 9.8 +/- 1.4 ml/h to 3.7 /- 0.8 ml/h (N = 8), These results suggest that AT1 receptors play a r ole in the drinking behavior observed after central cholinergic stimul ation in rats.