INTRAVENOUS LOSARTAN INHIBITS THE INCREASE IN PLASMA LUTEINIZING-HORMONE AND WATER-INTAKE PRODUCED BY INTRAVENTRICULAR ANGIOTENSIN-11

In the presence of sex hormones, intraventricular injection of angiote nsin II in female rats increases luteinizing hormone (LH) secretion, a nd this response is blocked by intraventricular losartan. There is evi dence that in doses of 3 mg/kg or more systemically administered losar tan blocks brain as well as peripheral AT(1) angiotensin II receptors. Therefore, we tested the effect of intravenous losartan, 1 and 10 mg/ kg, on the LH response to intraventricular angiotensin II in ovariecto mized rats treated with estrogen and progesterone. The larger dose of losartan abolished the LH response. It also produced a marked reductio n in the drinking response to intraventricular angiotensin II. The dat a provide additional evidence that in larger doses, peripherally admin istered losartan can penetrate the brain, and support the hypothesis t hat in female rats, the brain renin-angiotensin system plays an excita tory role in the regulation of LH secretion.