Involvement of neurotransmitters in the 'anxiolytic-like' action of atrial natriuretic peptide in rats.
Effects of centrally administered rat atrial natriuretic peptide (ANP1-28) in different doses (50, 100, 150, 200, 500 or 1000 ng) were examined in rats with respect to anxiolytic properties in an elevated plus-maze model. In doses of 100, 150 and 200 ng, ANP1-28 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 rANP1-28 produced no behavioral effects in the elevated plus-maze model. Pretreatment with a dopaminergic blocker, an alpha-adrenoreceptor or a beta-adrenoreceptor antagonist antagonized the effect of 200 ng ANP1-28 in the elevated plus-maze test. A muscarinergic cholinergic blocker, a GABA receptor antagonist, a 5-HT receptor antagonist and an opiate antagonist were not able to modulate the 'anxiolytic-like' effects of ANP1-28. These results suggest that a multiple neurotransmitter system activation might be responsible for the ANP1-28-induced 'anxiolytic-like' activity.