The Role of Glucocorticoid’s System in Accumbens Nucleus on Learning and Memory Processes in Rat

  AA. Vafaei PhD ^1* , A. Jalal Medical Student ² , A. Rashidy Pour PhD ³

  1- Assistant Professor, Dept. of Physiology, Semnan University of Medical Sciences, Semnan, Iran

  2- Medical Student, Faculty of Medicine, Semnan University of Medical Sciences, Semnan, Iran

  3- Associated Professor, Dept. of Physiology, Semnan University of Medical Sciences, Semnan, Iran

  Background: Previous study indicated that glucocorticoid’s receptors (GRc) in accumbens nucleus (AN) probably are involved in modulation the processes of emotional memory storage. The aim of the present work was to determine the effect of agonist and antagonist of GRc on the modulation of memory processes (Acquisition, Consolidation and Retrieval) in AN of rat in Passive Avoidance Learning (PAL) model.

  Materials and Methods: This experimental study was carried out on 120 (12 groups) male Albino Wistar rats (220 – 250 g body weight). Two cannulae implanted bilaterally at the AN and after week the animals were trained in PAL. Corticosterone (1 µg/µl/side) as an agonist and RU38486 (3ng/µl/side) as an antagonist of GRc were injected bilaterally before, immediately after the training and before the retrieval test. Control rats received the same volume of Vehicle. Two days later, retention test was done and Step-through Latency to the dark chamber and total time that spend in light chamber in 10 minutes used as two criteria for measurement of memory.

  Results: Results indicated that bilateraly injection of agonist and antagonist of GRc immediately after training enhanced and impaired the memory consolidation respectively (P<0.01). But injection these drugs before the training and before the retrieval test had not significant effects on emotional memory processes.

  Conclusion: Findings of this experiment showed that glucocorticoid’s receptors in AN have important role in memory consolidation of new emotional data in PAL.

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  Key words: Accumbens nucleus, Learning and memory, Corticosterone, RU38486, Rat

  *Corresponding author, Tel: (0231) 3332080

  Journal of Rafsanjan University of Medical Sciences and Health Services, 2003, 3(1), 25-33