Abstract
We studied the roles of spinal cord endorphins and GABA in mediating electroacupuncture(EA) antinociception in rats, using low frequency/high intensity EA. In addition we developed a transcutaneous electrical nerve stimulation(TENS) device called Codetron for human patients using similar parameters (low frequency/high intensity), and tested it against conventional EA in patients with chronic pain.
Rats were anesthetized with continuous infusion of pentobarbital. Low frequency (4 Hz) high intensity (25x threshold) EA was applied for 15 minutes via needles to the 1st dorsal interosseus muscle, in order to suppress tail flick reflexes elicited by radiant heat. An intrathecal cannula was used to apply drugs to the cord. Naltrexone given before EA treatment prevented EA antinociception, but naltrexone given after EA failed to reverse the EA effect. Picrotoxin blocked EA effects, while diazepam enhanced EA antinociception.
In the human study, patients with chronic pain (N=171) were randomly assigned to one of two treatment groups: one receiving Codetron (TENS) treatments twice a week for 6 weeks, the other receiving a similar course of EA (with needles). In the short term (6 weeks) Codetron performed as well as EA. but in the long term followup (4—8 months) Codetron outperformed EA by a wide margin.
We conclude in the rat studies that antinociception from low frequency/high intensity stimulation is mediated by spinal cord endorphins and GABA. Moreover the endorphin effect produces a modulation which is preventable but not reversible by naltrexone. In the human study, Codetron was a successful means of delivering low frequency/high intensity TENS. Moreover, Codetron outperformed EA perhaps because it was designed to give high intensity stimulation without undue discomfort to the patients.
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