FOREBRAIN ANGIOTENSIN TYPE-1 RECEPTORS AND PARABRACHIAL SEROTONIN IN THE CONTROL OF NACL AND WATER-INTAKE

This study investigated the roles of serotonin (5-HT) receptors in the lateral parabrachial nucleus (LPBN), and brain angiotensin type 1 (AT (1)) receptors in the intake of 0.3 M NaCl and water induced by angiot ensin II (ANG II). Rats were implanted with stainless steel cannulas f or injections into tho subfornical organ (SFO) and into the LPBN. Bila teral LPBN pretreatment with the nonselective serotonergic 5-HT1/5-HT2 receptor antagonist methysergide (4 mu g/200 nl) markedly enhanced 0. 3 M NaCl intake induced by injections of ANG II (20 ng/200 nl) into th e SFO. Pretreatment of the SFO with the AT(1) receptor antagonist losa rtan (1 mu g/200 nl) blocked the intake of 0.3 M NaCl induced by ANG I I in combination with LPBN methysergide injections. These results sugg est that serotonergic mechanisms associated with the LPBN inhibit the expression of salt appetite induced by ANG II injections into Ihs SFO. In addition, the results indicate that the enhanced NaCl intake gener ated by central administration of ANG II in the presence of LPBN 5-HT blockade is mediated bg brain ATI receptors.