Angiotensin II-induced thirst, but not sodium appetite, via AT1 receptors in organum cavum prelamina terminalis.

The angiotensin receptor specificity, with respect to fluid intake, of the organum cavum prelamina terminalis (OCPLT), a recently discovered discrete forebrain structure with high sensitivity to angiotensin II (ANG II), was investigated. ANG II (10 ng) microinjected into the OCPLT significantly increased water consumption but did not induce intake of a hypertonic (3%) NaCl solution. Losartan, an ANG II type 1 (AT1) receptor-specific antagonist, produced dose-related (1-100 ng) inhibition of ANG II-induced drinking. The ANG II type 2 receptor-specific antagonist CGP-42112A was ineffective. Intake of the 3% NaCl solution in response to microinjection of either of the antagonists into the OCPLT was never observed. These findings suggest that water intake produced by microinjection of ANG II into the OCPLT is mediated by AT1 receptors uniquely and that, in contrast to other regions of the brain, these receptors do not induce salt intake when stimulated by ANG II.