ABSTRACT
Background and purpose: Nowadays repeated transcranial magnetic stimulation [rTMS] is being used as a treatment for some neurological disorders, but its effect on neuronal activity and synaptic plasticity has not been completely determined. The purpose of this study was to evaluate the effect of chronic rTMS on the ability of synaptic plasticity.
Materials and Methods: rTMS was applied to the hippocampal region for 14 days. One week following termination of rTMS, the amount of synaptic long-term potentiation [LTP] in animals was investigated and compared with control group. High-frequency stimulation [HFS] was applied to the perforant path for LTP induction, andfield potentials were recorded from granular layer of the dentate gyrus. Baseline field potential was recorded 10 minutes before HFS. An increase of at least 20% in population spike amplitude was measured as an index of synaptic potentiation.To compare the effects of rTMS on measured parameters, we used t-test and two way ANOVA followed by Benferroni test [Prism 8 software].
Results: Obtained data showed that, following 14 days of rTMS application causeda reduction in population spike amplitude compared to the control group [P<0.05].In addition, the ability of neurons generating LTP was reduced compared to the control group [P<0.001]. Paired pulse index measurement also showed thatthe paired-pulse facilitationdid not change following LTP induction in animals whom had received rTMS. However, there was a decrease in paired pulse facilitation in control group.
Conclusion: Chronic rTMS application reducesthe amount of synaptic potentiation. Considering the important role of LTP in the occurrence of cognitive processes, patterns of rTMS that have less effects on the ability of synaptic plasticity should be found.