The effects of atrial natriuretic peptide on the open-field activity of rats. The role of neurotransmitters.

In the present study, four doses (50, 100, 200 or 500 ng per animal) of rat atrial natriuretic peptide (rANP1-28) were tested on the open-field activity of rats following i.c.v. application of the peptide. ANP in doses of 200 ng or 500 ng/rat significantly increased the ambulation activity 15 min after the treatment. However, the effect was transitory; 30 min after application it was no longer observed. When the experimental animals were pretreated with different receptor blockers in doses which per se could not affect the behavioral paradigm, the effect of ANP was completely blocked by haloperidol (a dopaminergic blocking agent), phenoxybenzamine (an alpha-adrenergic blocker) and propranolol (a beta-adrenergic blocker). Atropine, naloxone, bicuculline and methysergide were ineffective. These results suggest that dopaminergic and adrenergic transmitter systems are involved in the ANP-induced locomotor activity of rats.