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Background and Objective: Dentate gyrus is a part of hippocampal formation that plays an important role in memory and learning. Astrocytes are one of the important glial cells in nervous tissue that play a more active role in neuronal activity, including regulating ion flux currents, energy production, neurotransmitter release, and synaptogenesis. The aim of this study was to determine the spatial memory effect on the number of astrocytes in Rat’s dentate gyrus. Materials and Methods: This experimental study, was done on 18 male Wistar Rats with using Morris water maze and Reference and Working memory methods. After spatial learning the Rat's brains was carried out and histological preparation was carried out, the slices were with PTAH method. The data analyzed, using T-test and One-way ANOVA. Results: The results showed significant difference in astrocytes number in dentate gyrus area between Reference memory (300.57±5.98) and control (73.73±22.61) groups (P<0.05). The difference between working memory (375.77±4.11) and control groups was significant. Comparing two groups there was a significant difference of number of astrocytes cell between the working memory and Reference memory group (P<0.05). Conclusion: This study showed that spatial learning such as Reference memory and Working memory increase the number of astrocytes in dentate gyrus and this increase can be due to duration of learning.

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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.

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Background and Objective: Hippocampus is the main region in cortex of the brain that involved in epilepsy. This study was done to determine the effect of intraventricular injection of vitamin C on histological structure of dentate gyrus of hipocampus in adult male epileptic rats.

Methods: In this experimental study, 40 adult male rats were randomly allocated into 5 groups (n=8). Animals in three groups were received vitamin C at dose (12.5, 25 and 50 mg/kg/bw) during 28 days, intraventricularly after were kindled by (pentylentetrazol; 40 mg/kg). Animals in forth group were received normal saline after were kindled by (pentylentetrazol; 40 mg/kg). Animals in the fifth group were received normal saline. After 28 days, rats were anesthetized by ketamin, then structure of hypocamp dissected. Histological passage was done in samples and coronal section was carried out. The sections of samples were stained by Hematoxyline-eosin. Forty fields systematicly were counted the normal neurons in dentate gyrus. Morphological change was determined by immunohistochemical method.

Results: The mean  number of normal neurons in dentate gyrus in epileptic rats which  received 25 g/kg vitamin C was more than animals in groups which were received doses of 12.5, 25 and 50 mg/kg vitamin C (P<0.05). This mean number of normal neurons in dentate gyrus of hypocamp in epileptic rats which received normal saline was lower than control and other experimental groups (P<0.05). Extensive morphological change in neurons of dentate gyrus in epileptic rats which received normal saline were observed (P<0.05). The lowest  morphological change were observed in neurons of dentate gyrus in epileptic rats which received at dose 25 mg/kg vitamin C in compared to the other groups (P<0.05).

Conclusion: Intraventricular injection of vitamin C in epileptic rat's dose dependly had neuroprotective effect on dentate gyrus neurons.