[Effect of Electroacupuncture Intervention on Expression of Synaptic Plasticity-related Molecules in Amygdala in Chronic Pain-negative Affection Rats].

OBJECTIVE

To observe the effect of electroacupuncture (EA) on expression of synaptic plasticity-related glutamate N-methyl-D-aspartate (NMDA) receptor subunit NR 1, gamma-aminobutyric acid (GABA) receptor subunits (Aβ 2, B 1), etc. in the amygdala in chronic neuropathic pain negative affection (CNPPNA) rats, so as to reveal its mechanism underlying pain relief.

METHODS

Male Wistar rats were randomized into normal control, CNPPNA model, EA, and anesthesia+EA (AEA)groups (=14 in each group, 8 for quantitative RT-PCR and 6 for immunofluorescence staining). The CNPPNA model was established by ligation of the left sciatic nerve and repeated electrical stimulation of the hindpaw plantar skin in the pain-paired compartment. EA was applied to bilateral "Zusanli"(ST 36)and "Yanglingquan"(GB 34)for 30 min, once daily for 7 days.Thermal pain threshold (paw withdrawal latency, PWL)of the bilateral paws was measured by using a Tail-Flick Unit. The conditioned place aversion (CPA) was determined by using a CPA-paired compartment. The expression levels of GABAAβ 2, GABAB 1, NMDA receptor subunit NR 1, postsynaptic density-95 protein(PSD-95), Piccolo genes in the right amygdala area were determined using quantitative RT-PCR, and the immunoactivity of metabotropic glutamate receptor subunit 1 (mGluR 1) and GABAB 2 in the basolateral amygdala (BLA) nucleus was detected using immunofluorescence staining.

RESULTS

After modeling, PWL difference (PWLD) values of the model group were significantly increased (<0.001),and the time spent in the CPA-paired compartment was considerably decreased compared with the control group (<0.001).After EA intervention for 3 and 7 days, the PWLD levels of both EA and AEA groups were apparently decreased(<0.05),and the time spent in the CPA-paired compartment was apparently increased in the EA and AEA groups(<0.05),suggesting a pain relief and an improvement of the negative affection after EA intervention. Additionally, following EA, the apparently-decreased expression levels of GABAAβ 2,GABAB 1,PSD-95,Piccolo genes and the reduced numbers of GABAB 2 positive cells and NMDA-NR 1 mRNA as well as mGluR 1 positive fiber numbers were remarkably increased in the EA group (<0.05, <0.001).The expression levels of Piccolo gene, GABAB 2 and mGluR 1 positive cells/fiber numbers were apparently lower in the AEA group than in the EA group (<0.001). No significant differences were found between the EA and AEA groups in the PWLD, time spent in the CPA-paired compartment, and the expression levels of NMDA-NR 1, GABAAβ 2, GABAB 1 and PSD-95 genes (>0.05).

CONCLUSIONS

Repeated EA stimulation of ST 36-GB 34 has a role in relieving both sensory and affection dimensions of chronic pain in CNPPNA rats, which Feb be respectively related to its effects in up-regulating the expression of GABAAβ 2, GABAB 1, NMDA-NR 1, PSD-95 and Piccolo genes, and in promoting the expression of mGluR 1 and GABAB 2 proteins and Piccolo gene in the amygdala.