Influence of TENS on autonomic function

This study investigates the autonomic effects of transcutaneous electrical nerve stimulation (TENS) in pain-free volunteers. Previous experiments that electroacupuncture produces a transient segmental increase in sympathetic tone followed by a long-term centrally mediated sympathetic inhibition. Increasingly, emphasis is placed on the involvement of the sympathetic nervous system in pain modulatory mechanisms. The review of the literature reveals contradictory results regarding sympathetic effects of TENS, including activation, inhibition and no effect. We monitored heart rate, systolic and diastolic blood pressures, skin impedance and computerized thermograms of face, arm and leg during double-blind sham and real TENS at both upper and lower extremities. We compared these effects to those evoked by a stressful stimulus (10 sec loud unpredictable aversive noise at about 3 min intervals).