Abstract

Objetives: Previously, we observed that the injection of glutamate antagonists injected within the Nucleus Accumbens Septi(NAS) produced an anxiolytic-like effect in the elevated plus maze (EPM) test in basal non-disturbed state rats. The effect of metoprolol, a specific Beta-1 Adrenoreceptor antagonist in the EPM, was studied previously in a resting condition in male rats bilaterally cannulated in the NAS. Methods: Rats were previously submitted to restrain stress and divided into four groups. They received bilaterally 1 μl injections of saline (n=13) or atenolol in different doses within the NAS: 0.75 (n=15), 1 (n=13) and 2μg/1 μl (n=13), 15 min before testing. Rats were maintained under restrain between injection and test. Results: Time Spent in the Open Arm (TSOA) was modified by treatment (F = 4.239, p = 0.0096, df = 3) and increased by the medium dose group when it was compared with the saline group (p<0.05) and the lowest dose group (p<0.01). Open arms entries (OAE) were modified by treatment (F = 3.461, p = 0.0231, df = 3). This parameter was increased by the medium dose of atenolol (p<0.05) when compared to saline andthe lowest dose. No significant differences were observed in other parameters studied. Conclusion: We conclude that atenolol beta-1 receptor blockade within the NAS after restraint leads to an anxiolytic-like effect related to an increase in the Time Spent in the Open Arm (TSOA), and behavioural disinhibition, evidenced in the increase in the Open Arm Entries (OAE), showing a specific behavioural pattern.