Local transcutaneous electrical stimulation (TENS) effects in experimental inflammatory edema and pain

Few studies in the literature associated transcutaneous electrical stimulation (TENS) use with an antiinflammatory activity. The purpose of this study was to investigate the effects of low (10 Hz)- and high (130 Hz)-frequency TENS on hyperalgesia and edema that occur after injection of carrageenan in rat paw. After induction of inflammation, either low- or high-frequency TENS was applied in the rat paw for 20 min, and the effect of TENS treatment on escape or paw withdrawal and edema was measured. Both low- and high-frequency TENS inhibited by 100% the hyperalgesia but not the edema response. However, low-frequency TENS presented longer lasting effect as compared with high-frequency TENS. Naltrexone-treated animals showed a complete reversion of the analgesic effect induced by low- but not high-frequency TENS. Thus, our data demonstrated absence of an antiinflammatory effect associated to TENS use and confirmed the participation of endogenous opioids on low TENS-induced analgesia.