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Background & Objective: In addition to pyramidal neurons and interneurons, the hippocampus contains Astrocytes that play important roles in regulating ion flux currents, energy production, neurotransmitter release and memory. Learning needs some instrument for information storage and information maintenances mechanisms resemble to memory. The aim of this study was determination of spatial memory effect on the number of astrocytes in rat’s hippocampus. Materials & Methods: In this experimental study, with usage of Morris Water Maze and Reference memory technique, we used 10 male albino wistar rats. 5 rats were in control group and 5 rats in Reference memory group. After histological preparation, the slides were stained with PTAH staining for showing the Astrocytes. Results: The findings of this study showed significant difference in astrocytes number in CA1, CA2 and CA3 area of hippocampus between control and reference memory group. The mean and SD of astrocytes in CA1, CA2 and CA3 of reference memory group were 118.57±25.29, 58.91±23.59 and 116.6±31.14, that they are more than control group with 49±17.29 in CA1, 48.8±25.21 in CA2 and 41.95±11.22 in CA3. Conclusion: We concluded that the number of astrocytes increased due to spatial learning (e.g. reference memory method).

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Background and Objective: Morphological alterations of hippocampus and dentate gyrus due to opium were reported in humans and animals. Also other evidences have shown that astrocytes actively participate in synaptic plasticity. This study was done to determine the conditioning place preference (CPP) on astrocytes number of Rat dentate gyrus by immunohistochemical technique.

Materials and Methods: In this experimental study, 48 male Wistar Rat weighted average 220-250 g were used. For behavioural tests, Rats divided into eight experimental groups. The Rats were received morphine at different doses (2.5, 5, 7.5 mg/kg) for three days by subcutaneous injection and sham groups, received saline dose (1 mg/kg) and then CPP test in them were investigated. 48 hours after behavioural testing animals were decapitated under chloroform anesthesia and their brains fixed and after tissue processing, slices stained with immunohistochemistery techniques. For morphometric study PTAH staining of astrocytes was used.

Results: The most dose responses of morphine was observed in 7.5mg/kg. The number of astrocytes in the controls (20.627±6.129) was similar to control-saline group (17.339±4.71). This difference was not significant, while the difference in the number of astrocytes in control group with morphine-treated experimental groups was significant (P<0.05).

Conclusion: We concluded that the phenomenon of conditioned place preference induced by morphine can cause a significant increase in the number of astrocytes of sham and experimental groups compared to controls.