The Effect of Gallic Acid on Passive Avoidance Memory, Working Memory, and Dark Neuron Cell Density in CA1/CA3 Areas in Rats Hippocampal Degeneration Model

Trimethyltin (TMT) intoxication with hippocampal degeneration induces the production of dark neurons in different areas of the hippocampus. The present study assessed the effect of Gallic acid (GA) on working memory, avoidance memory, and the density of dark neurons in the CA1/CA3 regions of the rat hippocampus following TMT intoxication. In this study, 32 adult male Wistar rats were randomly assigned to four groups including control, TMT+NS, TMT+GA100, and TMT+GA200. GA at doses of 100 and 200 mg/kg per body weight was administered orally 24 hours after TMT injection (8 mg/kg). The Y-maze was used to assess the working memory and the shuttle box was used to measure avoidance memory. The density of dark neurons in CA1 and CA3 regions of the hippocampus was then assessed by dissector method. Moreover, in order to determine the existence of significant differences between the groups, one-way ANOVA and Tukey’s post hoc test were used and p <0.05 was considered statistically significant. There was a significant decrease in the percentage of alteration behavior, delay in entering the dark room of shuttle box, along with an increased density of dark neurons in the TMT+NS group compared to the control group (p<0.001). While, administration of GA ameliorated the working and avoidance memory and reduced the density of CA1/CA3 dark neurons in the hippocampus compared to TMT+NS group (p˂0.001). GA administration appears to improve cognitive symptoms following TMT intoxication by reducing neuronal damage to CA1/CA3 areas of the hippocampus..