LOCALIZATION OF CHANGES IN IMMEDIATE-EARLY GENES IN BRAIN IN RELATIONTO HYDROMINERAL BALANCE - INTRAVENOUS ANGIOTENSIN-II

Immediate early genes, detected by Fos- and Jun-like immunoreactivity (FLI, JLI), were induced in discrete regions of the rat brain by intra venous infusion of angiotensin II (Ang II) at dipsogenic doses. The re gions included subfornical organ (SFO), organum vasculosum laminae ter minalis (OVLT), median preoptic nucleus (MnPO), supraoptic nucleus (SO N), and the magnocellular part of the paraventricular hypothalamus (PV H). These responses were sustained for up to 6 h of infusion. In SFO, FLI was induced preferentially in the posterior part, while JLI occurr ed in more central regions. Cerebroventricular (ICV) injection of the Ang II type 1 receptor (AT-1) antagonist, losartan potassium, complete ly prevented the FLI induced by Ang II in these brain regions. ICV inj ection of the Ang II type 2 receptor (AT-2) antagonist, PD 123319, did not reduce Ang II-induced FLI in SFO, OVLT and MnPO, but markedly att enuated the activation in SON and PVH. To determine whether SFO is the primary site for transduction of the circulating Ang II signal, elect rolytic lesions were made in or rostral to the SFO. Rats with complete lesions showed a complete absence of Ang-induced FLI in SON and PVH. The data are discussed in terms of functional mapping of the brain reg ions activated by circulating Ang II and neural circuitry for water in take, including the possible role of AT-2 receptors in PVH and SON.