The effects of peptide and nonpeptide angiotensin II-receptor ligands on the activity of brain monoamine oxidase in water-repleted rats.

The effects of i.c.v. administered peptide and nonpeptide ANG II-receptor ligands (losartan, EXP 3174, saralasin and sarmesin) on monoamine oxidase A (MAO-A) and MAO-B activities in the frontal cortex, striatum, hypothalamus and hippocampus of water-repleted rats were investigated. Alterations in MAO-A and MAO-B activities were found in different rat brain regions after ANG II which depended on the isoenzyme type and brain structure. MAO-A activity significantly increased in the frontal cortex and hypothalamus, brain regions containing AT1 receptors, mainly. MAO-A and MAO-B activities were affected differently by all studied ANG II-receptor ligands, which in most cases antagonized the effect of ANG II (losartan, an AT1-nonpeptide receptor antagonist being the most effective). There was no clearcut relationship between the inhibition of ANG II-induced water intake and the changes of MAO-A and MAO-B activities under the effect of the ANG II-receptor antagonists studied.