[Effect of electroacupuncture on the levels of amino acid neurotransmitters in the spinal cord in rats with chronic constrictive injury].

Objective: To observe the changes of amino acid neurotransmitter contents in the lumbar spinal cord after electroacupuncture (EA) in rats with neuropathic pain so as to study its spinal mechanism underlying pain relief.

Methods: Forty SD rats were randomly divided into control, sham surgery, model and EA groups (n=10). Chronic constrictive injury (CCI) (neuropathic pain) model was duplicated by ligature of the right sciatic nerve with a piece of catgut. EA (1-3 mA, 2 Hz) was applied to "Huantiao" (GB 30) and "Weizhong" (BL 40) on the injured side for 30 minutes, once a day for 7 days. The mechanical and thermal pain thresholds were measured before and after CCI, and after EA intervention. Concentrations of glutamate (Glu), aspartate (Asp), glutamine (Gln), gamma-aminobutyric acid (GABA), Glycine (Gly) and taurine (Tau) in the lumbar spinal cord (L4-6) were detected by O-phthaladehyde derivatization + high performance liquid chromatography (HPLC).

Results: Compared with the control group, both the mechanical and thermal pain thresholds of the model group were decreased significantly on day 10 and day 16 after CCI (P < 0.01). Compared with the model group, the mechanical and thermal pain thresholds in the EA group on day 16 after CCI were upregulated strikingly (P < 0.01). In comparison with the control group, Glu, Asp, Gin and GABA levels in the lumbar spinal cord were significantly higher in the model group (P < 0.05, P < 0.01), while Gly and Tau levels in the lumbar spinal cord were markedly lower in the model group (P < 0.05). In comparison with the model group, spinal Glu, Asp, and Gin contents were downregulated significantly in the EA group (P < 0.01), while Gly, GABA and Tau levels were upregulated obviously (P < 0.01, P < 0.05). No significant differences were found between the control and sham surgery groups in the mechanical and thermal pain thresholds, and in the spinal Glu, Asp, GIn, GABA, Gly and Tau levels (P > 0.05).

Conclusion: EA of GB 30 and BL 40 may alleviate neuropathic pain in CCI rats, which is closely with its effects in reducing the release of excitatory amino acids and promoting the release of inhibitory amino acid neurotransmitters.