Role of spinal adenosine A1 receptors in the analgesic effect of electroacupuncture in a rat model of neuropathic pain.

OBJECTIVE: The aim of this study was to determine the role of spinal adenosine A1 receptors (A1Rs) in the analgesic effects of electroacupuncture (EA) for neuropathic pain. METHODS: We performed EA for 30 minutes at the zusanli acupoint in the legs of rats with previously induced chronic constriction injuries and observed the mechanical and thermal pain thresholds 1 hour later. We also examined adenosine levels by high-performance liquid chromatography and A1R expression in the L4-6 spinal cord by western blot analysis. We then injected A1R short interfering RNA (AV-shA1RNA) into the L4-6 spinal cord to downregulate A1R expression and re-examined the mechanical and thermal pain thresholds. RESULTS: Adenosine levels and A1R expression in the L4-6 spinal cord were increased at 1 hour after EA. In addition, EA exhibited an analgesic effect that was reversed by AV-shA1RNA. CONCLUSIONS: Our results suggest that EA at the zusanli acupoint elicits an analgesic effect against neuropathic pain, mediated by A1Rs in the spinal cord.