Résumé
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.
Résumé
Different Tanacetum species have been widely used in traditional medicine as a remedy for the pain and inflammation since ancient times. Because of the few studies conducted on the mechanism of Tanacetum parthenium [TP], this study has been conducted to determine the effects of TP on pain relief and its action mechanism. In this experimental study, 100 male mice [25-35 g] were randomly grouped into receivers of distilled water, morphine [0.5 mg/kg], ibuprofen [100 mg/kg], different doses of the extract including 10, 20, 30 and 40 mg/kg of the extract. In order to study the pain relief effect of this herb, two groups were also received naloxon [0.5 mg/kg] and naloxon together with the 40 mg/kg of the extract. Animals were injected with 0.9% acetic acid for visceral pain induction. 15 minutes after each injection antinociceptive effects were recorded by counting the number of writhes for 30 minutes. Achieved data were analyzed by SPSS statistical software, Kruskal-Wallis and Dunn post hoc test. 40 mg/kg of the extract of TP caused a significant reduction in the pain response. Group receiving a dose of 40 mg/kg extract had higher antinociceptive effects than the group receiving ibuprofen [p<0.001] but it didn't have any significant difference with the group receiving morphine. Group receiving naloxone had a statistical significant difference with the group receiving 40 mg/kg extract with naloxone and the group receiving 40 mg/kg extract [p<0.001]. Antinociceptive activity of TP extract is due to the activation of opioid system, however further studies are needed to be conducted for finding out the suitable position or the role of the antispasmodic effect of TP