Long-lasting effect of transcutaneous electrical nerve stimulation on the thermal hyperalgesia in the rat model of peripheral neuropathy

We demonstrate here unexpectedly long-lasting effect of transcutaneous electrical nerve stimulation (TENS) to alleviate thermal hyperalgesia in rats with peripheral neuropathy produced by constriction of sciatic nerve. For TENS groups, electrical stimulation for 16.7 min (1 Hz, paired current, 12 mA, 5-ms interval, 0.2-ms duration, 999 pairs), once a day, was delivered for 5 consecutive days, under halothane anesthesia (Hal-TENS group) or pentobarbital anesthesia (Pent-TENS group). For non-TENS groups, only the anesthesia was delivered (Hal-no TENS group, Pent-no TENS group). For the control group, neither anesthetics nor TENS was delivered. To evaluate hyperalgesia, paw withdrawal latency (PWL) to radiant heat was measured before nerve constriction and five times after the constriction; just before TENS and at 1, 3, 7, and 14 days after the completion of TENS. Compared to the non-TENS groups, rats in the TENS groups showed significantly reduced thermal hyperalgesia at least for 3 days (Pent-TENS group) or for 7 days (Hal-TENS group) after TENS. These results indicate a possible long-lasting therapeutic effect of TENS applied under general anesthesia.