Investigation of the effects of transcranial direct current stimulation on learning and memory changes based on experimental cerebral ischemia model

Objective: In our study, we aimed to investigate the effects of Transcranial Direct Current Stimulation (tDCS) application on learning and memory and molecular mechanisms of rats with focal cerebral ischemia. Method: 100 male Wistar rats, each of which weighs 290-310 g, were divided into five groups as Sham, tDCS, Ischemia/Reperfusion (IR), IR+tDCS and IR+E-tDCS groups, with 20 rats in each group. Novel object recognition, object localization and Y-maze tests were used to evaluate learning and memory, and open field test was performed to evaluate locomotor activity. Glutamate and glutamine levels, AMPA, NMDA, VGLUT-1, EAAT-1, EAAT-2 and EAAT-3 mRNA expressions in hippocampus tissues were evaluated. Ischemic areas were analyzed by TTC staining. Results: Motor behavior index increased significantly in all groups where IR was applied on the first day of ischemia, but on the 7th day, it was significantly decreased in IR+tDCS and IR+E-tDCS groups compared to IR group. An increase was observed in IR+tDCS and IR+E-tDCS groups compared to the IR group while a significant decrease was observed in IR group in the locomotor activity, learning and memory test data. Glutamate and glutamine levels, AMPA and NMDA receptor expressions, VGLUT1 and EAAT1 mRNA expressions were found to be significantly higher in IR group, it was found to be significantly lower in IR+tDCS and IR+E-tDCS groups compared to IR group. While EAAT2 mRNA expression decreased significantly in IR group compared to sham group, EAAT3 mRNA expression did not change. EAAT2 and EAAT3 expressions were significantly higher in IR+tDCS and IR+E-tDCS groups compared to the IR group. Ischemic areas were significantly decreased in IR+tDCS and IR+E-tDCS groups compared to IR group. Conclusion: In our study, it has been shown that post-IR tDCS application improves learning and memory disorders and tDCS achieves these effects through the carriers that regulate glutamate level. Key words: ischemia reperfusion, tDCS, learning and memory, glutamate