Progesterone administration to ovariectomized rats reduces water and salt intake induced by central administration of angiotensin II

ABSTRACT

We tested the effects of estradiol, progesterone and testosterone on water and salt intake induced by angiotensin II (ANG II) injected into the third ventricle of female Holtzman rats weighing 250-300 g. The water and salt ingestion observed after 120 min in the control experiments (injection of 0.5µl of 0.15 M NaCl into the third ventricle) was 1.6 ñ 0.3 ml (N = 10) and 0,3 ñ 0.1 ml (N = 8) in intact rats, respectively, and 1.4 ñ 0.3 ml (N = 10) and 0.2 ñ 0.1 (N = 8) in ovariectomized rats, respectively. ANG II injected in intact rats (4, 6, 12, 25, and 50 ng, icv, in 0,5 µl saline) induced an increase in water intake (4.3 ñ 0.6, 5.4 ñ 0.7, 7.8 ñ 0.8, 10.4 ñ 1.2, 11.2 ñ 1.4 ml/120 min, respectively) ( N = 43). The same doses of icv ANG II in intact increased the 3 per cent NaCl intake (0.9 ñ 0,2, 1.4 ñ 0,3, 2,3 ñ 0.4, 2,2 ñ 0,3, and 2.5 ñ 0.4 ml/120 min, respectively) (N = 42). When administered to ovariectomized rats ANG II induced comparable amounts of water intake (4.0 ñ 0.5, 4.8 ñ 0.6 ñ 0.7, 9.6 ñ 0.8, and 10.9 ñ 1.2 ml/120 min, respectively (