Losartan influences behavioural effects of angiotensin II in rats

The role of the angiotensin AT1 receptors in certain behavioural effects of angiotensin II (Ang II), using their selective antagonist losartan (DuP 753), was assessed. Ang II, given intracerebroventricularly (ICV) at the dose of 1 nmole, significantly improved object recognition, learning of conditioned avoidance responses (CARs), and recall of a passive avoidance behaviour. Losartan alone (1 microgram) was ineffective in any test except for the elevated 'plus' maze measuring anxiety which was diminished by the drug, both in peptide treated and in control rats. Losartan, given 5 min before Ang II, abolished improved after the peptide recall of the passive avoidance and object recognition. Losartan did not influence increased after Ang II rate of CARs acquisition. None of the treatments significantly changed behaviour of rats in the open field. The results point to the considerable involvement of the AT1 angiotensin receptors in the cognition improving effects of Ang II. However, unspecific psychoactivity of losartan should also be taken into account.