بررسي اثر تزريق آكونيست و آنتاگونيست گلوكوكور تيكوييدي در ناحيه قشر اوربيتوفرونتال بر فرايند يادگيري و حافظه در موش بزرگ آزمايشگاهي

The effect of injection of glucocorticoid agonist and antagonist in the Orbitofrontal cortex on spatial memory of rats

Introduction: There is much evidence indicating that glucocorticoids receptors are highly involved in emotional learning and memory storage in many areas of the brain. The aim of the present study was to assess the role of glucocorticoid agonists and antagonists on the orbitofrontal cortex (OFC) in spatial memory processes (Acquisition, Consolidation and Retrieval) of the place avoidance learning task. Materials and Methods: Long-Evans strain rats, weighting 280-320 gr, (n=100, in 10 groups) were surgically implanted bilaterally with cannulae aimed at the OFC and were trained to avoid entrance to a 60 degree segment of the arena; entering this was punished by mild footshock. The forbidden sector was defined by room cues during rotation in the light and by floor cues in the dark. Place avoidance training occurred in a single 30-min session and avoidance memory was assessed during a 30-min extinction trials, 24 hours later. The time of the first entrance and the number of entrances into the punished sector during extinction were used to measure the place avoidance memory. Bilateral injections of Dexamethasone (0.1miug/0.6 pllside) as a glucocorticoid agonist and RU38486 (3ng/0.6 miul/side) as a glucocorticoid antagonist were injected to the OFC 5 min before acquisition, immediately, 60 and 120 min after training and 5 min before retrieval test. Control groups simultaneously received just the vehicle of the same volume, that was injected to the other groups. Results: The results indicated that acquisition, consolidation and retrieval of spatial memory were not impaired (P>0.05). Conclusion: The findings above showed that the glucocorticoid receptors in OFC do not have an important role in modulation and storage of spatial memory related to emotional events in place avoidance learning tasks.