Memantine improves memory and hippocampal proliferation in adult male rats

Abstract

Neurogenesis occurs during the embryological development of the brain. However, it is universally accepted that in all adult mammalian brains, there are two sites of high-density cell division: the subventricular zone of the lateral ventricles (SVZ) and the subgranular zone (SGZ) of the dentate gyrus of the hippocampal formation. Doxorubicin (DOX) is an anthracycline agent which results in cognitive deterioration and memory impairment, whereas memantine (MEM) is an NMDA receptor antagonist which is approved for the treatment of Alzheimer’s dementia. Many studies have revealed MEM’s positive impact on memory and demonstrated that it stimulates neuronal division in the hippocampus. This study aimed to assess the effect of MEM on spatial memory and neural proliferation in the hippocampus in adult male rats treated with DOX. For this purpose, forty male Sprague-Dawley rats were divided into four groups of ten rats each according to the agent: control, MEM (2.5 mg/kg), DOX (2 mg/kg), and DOX with MEM. The rats were given seven intraperitoneal injections every other day. We tracked the rat’s weights to assess the weight-reducing effects of the drugs. In order to test spatial memory, the rats were subjected to the novel location recognition (NLR) task 30 minutes after the last injection. Additionally, Ki67 immunohistochemistry was performed to examine hippocampal proliferation. The results showed a significant reduction in discrimination index (DI) in the DOX-treated group compared to MEM- (p < 0.001) and MEM with DOX-treated groups (p < 0.001). There was a significant increase in Ki67-positive cells in the MEM-treated group compared to the saline-treated group. Treatment with DOX impaired hippocampal proliferation compared to treatment with MEM or saline. The co-administration of MEM with DOX ameliorated the decline in hippocampal proliferation compared to treatment with DOX alone. There was a significant weight reduction in the DOX group in comparison to the control group, but MEM attenuated DOX-induced weight loss. Rats treated with DOX displayed a drop in memory, hippocampal proliferation, and weight compared to the MEM-treated group, whereas the co-administration of MEM with DOX protected memory, hippocampal proliferation, and doxorubicin-induced weight loss.

Keywords

• memantine
• doxorubicin
• memory
• hippocampus
• neurogenesis
• novel location recognition.