Impacto da eletroestimulação transcraniana em modelo animais de hiperalgesia induzida por estresse crônico variado

Abstract

The painful sensation affects quality of life and neurobiological systems may cause physical, behavioral and psychological changes. Of these, psychological factors such as stress, can directly influence the perception of painful sensations. The intensity of these responses will depend on the stress type to which an individual is exposed. In this context, the seeking for the treatment of painful symptoms remains a challenge. Recent studies indicate that the use of Transcranial direct-current stimulation (ETCC) has been used for the treatment of different pathologies. Thus, this study aims to investigate the use of 20-minutes ETCC during 8 days in the treatment of 24 male Wistar rats. Initially the animals were randomly divided into two groups, control and stress. The stress group underwent into a varied chronic stress protocol (ECV) which was validated by the test of sweet food consumption, the open field test and by the adrenal glands weight. Before starting ETCC treatment, animals of the control group and stress were divided into two treatment groups, sham and active ETCC stimulation (electrical current of 2 mA in the motor cortex area). For evaluation of the nociceptive response, the tail-flick test was applied before and after ETCC treatment. At the end of the experiment BDNF levels were measured in the hippocampus, as central measure, and, as peripheral measure, both dosages were according to ELISA method. Considering results for ECV protocol validation were, the sweet food consumption test showed anhedonia induction in stressed animals (p <0.02), the open field test had higher output latency of the first quadrant (p = 0.04) and reduced number of crossings (p = 0.003) for stressed group. The number of rearings showed no statistical difference between groups (p = 0.17). In addition, adrenal glands weight was higher in stressed animals (p = 0.003). Basal tail-flick test showed induction of hyperalgesia in stressed rats (p <0.001). No statistical difference between groups and treatments was showed immediately after (p = 0.21) and 24 hours after (p = 0.14) ETCC. Hippocampus BDNF levels in stressed animals treated with ETCC was higher compared to control groups and treatments (p = 0.007), statistical difference was observed in the peripheral BDNF levels between control group and stress (p <0.001) and treatment tDCS and sham (p <0.001). Our findings confirm effectiveness of ECV protocol in inducing hyperalgesia. Also, the potential of ETCC as an alternative to reverse low levels of BDNF caused by chronic stress.