[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 ( n =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 ( P <0.001),and the time spent in the CPA-paired compartment was considerably decreased compared with the control group ( P <0.001).After EA intervention for 3 and 7 days, the PWLD levels of both EA and AEA groups were apparently decreased( P <0.05),and the time spent in the CPA-paired compartment was apparently increased in the EA and AEA groups( P <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 ( P <0.05, P <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 ( P <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 ( P >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.