Repetitive Transcranial Magnetic Stimulation (rTMS) Reverses the Long-term Memory Impairment and the Decrease of Hippocampal Interleukin-10 Levels, both Induced by Neuropathic Pain in Rats

• Published in: Neuroscience 2021-09, Vol.472, p.51-59
• Main Authors: Toledo, Roberta Ströher, Stein, Dirson João, Stefani Sanches, Paulo Roberto, de Souza, Andressa, da Silva, Lisiane Santos, Medeiros, Helouise Richardt, de Souza Antunes, Mayra Angélica, de Castro, Josimar Macedo, Fregni, Felipe, Caumo, Wolnei, Torres, Iraci L.S.
• Format: Article
• Language: English
• Subjects: BDNF; brain stimulation; chronic pain; IL-10; memory; neuromodulation
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2021.07.030

[Display omitted] •Neuropathic Pain (NP) has been shown to impair long term memory (LTM).•rTMS is one of neuromodulatory techniques that induces satisfactory pain relief.•Low-frequency rTMS improves LTM impairments induced by NP in rodents.•LTM reversal may be related to increased levels of IL-10 in the hippocampus.•rTMS-induced changes are observed exclusively in animals with NP, not in naive animals. Neuropathic pain (NP) is characterized by the presence of spontaneous pain, allodynia and hyperalgesia. Repetitive transcranial magnetic stimulation (rTMS) is one of neuromodulatory techniques that induces satisfactory NP relief, including that from refractory pain patients. The objective of this study was to evaluate rTMS treatment over long term memory (LTM) and hippocampal BDNF and IL-10 levels in rats submitted to a NP model. A total of 81 adult (60-days old) male Wistar rats were randomly allocated to one of the following 9 experimental groups: control, control + sham rTMS, control + rTMS, sham neuropathic pain, sham neuropathic pain + sham rTMS, sham neuropathic pain + rTMS, neuropathic pain (NP), neuropathic pain + sham rTMS and neuropathic pain + rTMS. Fourteen days after the surgery for chronic constriction injury (CCI) of the sciatic nerve, NP establishment was accomplished. Then, rats were treated with daily 5-minute sessions of rTMS for eight consecutive days. LTM was assessed by the object recognition test (ORT) twenty-four hours after the end of rTMS treatment. Biochemical assays (BDNF and IL-10 levels) were performed in hippocampus tissue homogenates. rTMS treatment reversed the reduction of the discrimination index in the ORT and the hippocampal IL-10 levels in NP rats. This result shows that rTMS reverses the impairment LTM and the increase in the hippocampal IL-10 levels, both induced by NP. Moreover, it appears to be a safe non-pharmacological therapeutic tool since it did not alter LTM and neurochemical parameters in naive animals.