Correlation between neurotrophic activity and sensitivity to mechanical stimuli in immobilization stress model treated with transcranial direct current stimulation

Abstract

Stress causes biochemical and behavioral changes that can contribute to the genesis of diseases. Transcranial direct current stimulation modulates neuronal excitability. In the present study, the hypothesis that there is a correlation between the effects of tDCS on neurotrophic activity and the ability to increase the threshold for mechanical sensitivity was tested. Male Wistar rats were divided into ten groups: 1) Behavioral control (BeC); 2) Biochemical control (BiC); 3) Immobilization 30 (IMO30); 4) Immobilization 60 (IMO60); 5) Immobilization 120 (IMO120); 6) Immobilization 24h (IMO24h); 7) Immobilization + tDCS 30 (IMO+tDCS30); 8) Immobilization + tDCS 60 (IMO+tDCS60); 9) Immobilization + tDCS 120 (IMO+tDCS120); 10) Immobilization + tDCS 24h (IMO+tDCS24). Afterwards, they were submitted to the von Frey baseline behavioral test. In the following six days, they were submitted to the stress model by immobilization. On the seventh day, they received the last immobilization with the application of 20 minutes of tDCS or false stimulation with disconnected electrodes. Immediately after, they were subjected to the von Frey test 30, 60, 120 minutes and 24 hours after the session, then killed by decapitation with spinal cord collection for biochemical analysis. BDNF levels cord were assessed by Enzyme Linked Immunosorbent Assay (ELISA). There was a negative correlation between BDNF levels and mechanical sensitivity. The result show that tDCS can be an option to prevent effects of stress, however, studies still need to define adequate doses that the increase in BDNF is not exacerbated to the point of reducing the nociceptive threshold.