Electroacupuncture improves neuropathic pain: Adenosine, adenosine 5'-triphosphate disodium and their receptors perhaps change simultaneously

摘要

Applying a stimulating current to acupoints through acupuncture needles - known as electroacupuncture - has the potential to produce analgesic effects in human subjects and experimental animals. When acupuncture was applied in a rat model, adenosine 5'-triphosphate disodium in the extracellular space was broken down into adenosine, which in turn inhibited pain transmission by means of an adenosine A1 receptor-dependent process. Direct injection of an adenosine A1 receptor agonist enhanced the analgesic effect of acupuncture. The analgesic effect of acupuncture appears to be mediated by activation of A1 receptors located on ascending nerves. In neuropathic pain, there is upregulation of P2X purinoceptor 3 (P2X3) receptor expression in dorsal root ganglion neurons. Conversely, the onset of mechanical hyperalgesia was diminished and established hyperalgesia was significantly reversed when P2X3 receptor expression was downregulated. The pathways upon which electroacupuncture appear to act are interwoven with pain pathways, and electroacupuncture stimuli converge with impulses originating from painful areas. Electroacupuncture may act via purinergic A1 and P2X3 receptors simultaneously to induce an analgesic effect on neuropathic pain. Research Highlights Previous studies addressing the analgesic effect of acupuncture mainly focused on purine and a single purine receptor; no studies have examined the possible influence of synergism or antagonism with other receptors.Electroacupuncture may induce an analgesic effect in neuropathic pain by influencing both purinergic A1 and P2X purinoceptor 3 (P2X3) receptors simultaneously.Electroacupuncture analgesia may also involve adenosine and adenosine 5'-triphosphate disodium receptors in the peripheral and central nervous systems. Electroacupuncture can inhibit purinergic A1 and P2X3 receptors and exert an analgesic effect on neuropathic pain. Abbreviations ATP, adenosine 5'-triphosphate disodium; P2X3, P2X purinoceptor 3