In the present study, we investigated effects of intra-nucleus accumbens (intra-Nac) administrations of GABAA receptors agonist and antagonist, muscimol and bicuculline respectively, by themselves and their interaction with scopolamine on inhibitory avoidance (IA) memory consolidation and retrieval. This study used a step-through inhibitory avoidance task to assess memory in male Wistar rats. The results showed that post-training intra-NAc administrations of muscimol at doses of 0.01 and 0.02 µg/rat impaired IA memory consolidation, but bicuculline at different doses (0.1, 0.2 and 0.4 µg/rat) had no effect. Post-training inta-NAc injections of scopolamine at dose of 0.5 µg/rat not only impaired IA memory consolidation by itself but also in combination with an ineffective dose of muscimol showed an increase in impairing effect on IA memory consolidation. On the other hand, post-training intra-NAc injections of bicuculline fairly to completely prevented the impairing effect of higher doses of scopolamine on IA memory consolidation. In other sets of experiments, the results showed that pre-test intra-NAc administrations of not only muscimol (0.01 and 0.02 µg/rat), but also bicuculline (0.001, 0.01 and 0.1 µg/rat) impaired IA memory retrieval. The results also showed that pre-test intra-NAc administrations of scopolamine (0.25 and 0.5 µg/rat) impaired IA memory retrieval, and its co-administrations with an ineffective dose of muscimol (0.005 µg/rat) showed more impairing effect on IA memory retrieval. Pre-test intra-NAc administrations of bicuculline could not prevent the impairing effect of scopolamine on IA memory retrieval. Taken together, it can be concluded that the impairing effect of scopolamine on IA memory in the NAc is mediated, at least partly, via a GABAA system.
