INVOLVEMENT OF NEUROTRANSMITTERS IN THE ANXIOLYTIC-LIKE ACTION OF ATRIAL-NATRIURETIC-PEPTIDE IN RATS

Effects of centrally administered rat atrial natriuretic peptide (ANP( 1-28)) in different doses (50, 100, 150, 200, 500 or 1000 ng) were exa mined in rats with respect to anxiolytic properties in an elevated plu s-maze model. In doses of 100, 150 and 200 ng, ANP(1-28) abolished the normal preference for the closed arms of the maze, and increased the percentage of time spent on the open arms; this is consistent with an 'anxiolytic-like' effect. Doses of 50, 500 and 1000 ng of rANP(1-28) p roduced no behavioral effects in the elevated plus-maze model. Pretrea tment with a dopaminergic blocker, an alpha-adrenoreceptor or a beta-a drenoreceptor antagonist antagonized the effect of 200 ng ANP(1-28) in the elevated plus-maze test. A muscarinergic cholinergic blocker, a G ABA receptor antagonist, a 5-HT receptor antagonist and an opiate anta gonist were not able to modulate the 'anxiolytic like' effects of ANP( 1-28). These results suggest that a multiple neurotransmitter system a ctivation might be responsible for the ANP(1-28)-induced 'anxiolytic-l ike' activity.