LOSARTAN INFLUENCES BEHAVIORAL-EFFECTS OF ANGIOTENSIN-II IN RATS

The role of the angiotensin AT(1) receptors in certain behavioural eff ects of angiotensin II (Ang II), using their selective antagonist losa rtan (DuP 753), was assesssed. Ang II, given intracerebroventricularly (ICV) at the dose of 1 nmole, significantly improved object recogniti on, learning of conditioned avoidance responses (CARs), and recall of a passive avoidance behaviour. Losartan alone (1 mu g) was ineffective in any test except for the elevated 'plus' maze measuring anxiety whi ch was diminished by the drug, both in peptide treated and in control rats. Losartan, given 5 min before Ang II, abolished improved after th e peptide recall of the passive avoidance and object recognition. Losa rtan did not influence increased after Ang II rate of CARs acquisition . None of the treatments significantly changed behaviour of rats in th e open field. The results point to the considerable involvement of the AT(1) angiotensin receptors in the cognition improving effects of Ang II. However, unspecific psychoactivity of losartan should also be tak en into account. (C) 1996 The Italian Pharmacological Society.