MDMA or ecstasy is a derivative of amphetamines used mostly by young people worldwide. Although the acute effects of this drug are known, the effect of chronic administration is not well studied. Therefor the aim of this study was to determine the effects of repeated (long term) administration of MDMA on rats' memory and their hippocampal cell density.

In the present study, the role of gonadectomy on memory impairment and the density of androgen receptor-immunoreactive neurons in rats' hippocampus as well as the ability of testosterone to compensate of memory and the density of androgen receptors in the hippocampus was evaluated.

The change of steroid levels may also exert different modulatory effects on the number and class of serotonin receptors present in the plasma membrane. The effects of chronic treatment of testosterone for anxiety were examined and expression of 5-HT2A serotonergic receptor, neuron, astrocyte, and dark neuron density in the hippocampus of gonadectomized male mice was determined. Thirty-six adult male NMRI mice were randomly divided into six groups: intact-no testosterone treatment (No T), gonadectomy (GDX)-No T, GDX-Vehicle, GDX-6.25 mg/kg testosterone (T), GDX-12.5 mg/kg T, and GDX-25 mg/kg T. Anxiety-related behavior was evaluated using elevated plus maze apparatus. The animals were anesthetized after 48 hours after behavioral testing, and decapitated and micron slices were prepared for immunohistochemical as well as histopathological assessment. Subcutaneous injection of testosterone (25 mg/kg) may induce anxiogenic-like behavior in male mice. In addition, immunohistochemical data reveal reduced expression of 5-HT2A serotonergic receptor after gonadectomy in all areas of the hippocampus. However, treatment with testosterone could increase the mean number of dark neurons as well as immunoreactive neurons in CA1 and CA3 area, dose dependently. The density of 5-HT2A receptor-immunoreactive neurons may play a crucial role in the induction of anxiety like behavior. As reduction in such receptor expression have shown to significantly enhance anxiety behaviors. However, replacement of testosterone dose dependently enhances the number of 5-HT2A receptor-immunoreactive neurons and interestingly also reduced anxiety like behaviors.

Vitamin E may have beneficial effects on oxidative stress and Aβ-associated reactive oxygen species production in Alzheimer's disease. But, the exact role of vitamin E as a treatment for Alzheimer's disease pathogenesis still needs to be studied. Hence, we examined the therapeutic effects of vitamin E on the density of congophilic amyloid plaques and neurofibrillary tangles in rats' hippocampi.

The regular extract of Ginkgo biloba has been shown to possess neuroprotective properties in disorders like hypoxia, ischemia, seizure activity and peripheral nerve damage. Also, G. biloba has received attention as a potential cognitive enhancer for the treatment of Alzheimer's disease, but there is not any documentation about the effect of an extract of G. biloba on astrocytes. Therefore, the aim of this study was examined the effects of G. biloba extract on the rat's hippocampal astrocytes after scopolamine based amnesia. In this study, 36 adult male Wistar rats were used. Rats were randomly distributed into control, sham, protective and treatment groups. The rats in the sham group only received scopolamine hydrobromide (3 mg/kg) intraperitoneally. The rats in the protective and treatment groups received G. biloba extract (40, 80 mg/kg) for 7 days intraperitoneally before and after scopolamine injection. Forty eight hours after the last injection, the brains of the rats were withdrawn and fixed with paraformaldehide, and then after histological processing, the slices were stained with phosphotungstic acid-haematoxylin for astrocytes. Data were analyzed by the analysis of variance (ANOVA) post hoc Tukey test; P<0.05 was considered significant. Results showed that scopolamine can reduce the number of astrocytes in all areas of hippocampal formation compared with the control. However, G. biloba extract can compensate for the reduction in the number of astrocytes in the hippocampus before or after the encounter with scopolamine. We concluded that a pretreatment and treatment injection of G. biloba extract can have a protective effect for astrocytes in all areas of hippocampal formation.

A close interaction exists between the brain opioid and serotonin (5-HT) neurotransmitter systems. Brain neurotransmitter 5-HT plays an important role in the regulation of reward-related processing. However, a few studies have investigated the potential role of 5-HT2A receptors in this behavior. Therefore, the aim of the present study was to assess the influence of morphine and Conditioned Place Preference (CPP) on the density of 5-HT2A receptor in neurons of rat hippocampal formation.

Amyloid β plaques, in Alzheimer's disease, are deposits in different areas of the brain such as prefrontal cortex, molecular layer of the cerebellum, and the hippocampal formation. Amyloid β aggregates lead to the release of cytochrome c and finally neuronal cell death in brain tissue. hCG has critical roles in brain development, neuron differentiation, and function. Therefore, we investigated the effect of hCG on the density of the congophilic Aβ plaque and cytochrome c-ir neurons in the hippocampus, prefrontal cortex, and cerebellum of Streptozotocin (STZ)-treated rats.