Efeitos da estimulação transcraniana por corrente contínua sobre parâmetros comportamentais e bioquímicos em ratos Wistar submetidos a um modelo de dor neuropática

Abstract

Neuropathic pain is caused by an injury to the somatosensory nervous system, generating an important impact on the lives of patients affected with this condition. Preclinical and clinical studies have demonstrated the efficacy of transcranial direct current stimulation (tDCS) in promoting pain relief. However, the effects produced by tDCS has still been researched. Thus, the aim of this study was to evaluate the effects of tDCS on behavioral, morphological and biochemical parameters in rats with 30 and 60 days with unilateral chronic constriction of the sciatic nerve. Fourteen days after inducing the lesion, the rats were treated with 8 consecutive sessions of bimodal tDCS, lasting 20 minutes each session. The mechanical hypersensitivity test was applied a day prior to the beginning of experiments, 14 days after the surgery and 24 hours and 8 days after the end of the treatment. Eight days after the last tDCS session, the rats were euthanized and the prefrontal cortex, spinal cord and whole blood were collected. After performing the analyses, it was possible to verify that the pain model produced mechanical hyperalgesia 14 days after induction of the lesion in rats of 30 and 60 days and that bimodal tDCS reduced this effect 24 hours after the end of treatment (short-term effect) for 30-day rats and 7 days after the end of treatment (long term effect) for 60-day rats. In 30-day-old rats, it was observed a pain effect over spinal cord brain-derived neurotrophic factor (BDNF) spinal levels of rats with neuropathic pain, with no changes in the cortical and serum levels, neither a tDCS effect. In 60-day rats, the pain model promoted an increase in reactive oxygen species (RS) levels and a decrease in superoxide dismutase (SOD) in the prefrontal cortex. In the spinal cord, an increase in the total content of the thiols were reversed by tDCS effects. A decrease in nitrite levels and in glutathione-S-transferase (GST) activity was diminished by tDCS, however, a similar effect was observed in rats with the lesion that received sham stimulation. At the serum level, an increase in RS and thiobartituric acid reactive substances (TBARS) levels and a reduction in butyrylcholinesterase (BuChE) activity were observed, promoted by neuropathic pain. In conclusion, neuropathic pain model modified different biomarkers levels in study and tDCS demonstrated the efficacy in modulates these biomarkers e in promotes pain relief in rats of different phases of development.