DUANMU ChengLin, WANG Junying,YAN Yaxia, GAO Y onghui, ZHANG Jianliang, LIU Jun-ling

(Institute of Acu-moxibustion, China Academy of Chinese Medical Sciences, Beijing 100700)

Abstract: Objective:To observe the effect of electroacupuncture(EA) on changes of emotional and sensory components of pain behavioral reactions.we also observed ultrastructural changes of synapses of amygdalal Neuronal  Cells  by  using  a  transmission  electron  microscopy,  so  as  to  reveal  the  mechanisms  of  EA analgesia.Methods:Male  Wistar  rats  were  randomized  into  normal  control,  CNPPNA  model,  EA,  and anesthesia+EA (A+EA) groups (n=6 in each group)，The CNPPNA model was established by ligation of the left sciatic nerve and repeated electrical stimulation of the paw-bottom in the pain-paired compartment. EA  was  applied  to  bilateral  “Zusanli”(ST  36)  and  “Yanglingquan”(GB  34)  for  30min,  once  daily  for 7days. Thermal pain threshold (paw withdrawal latency, PWL) of the bilateral paws was measured by using a  Tail-Flick  Unit.  The  conditioned  place  aversion  (PLA)  was  determined  by  using  a  CPA-paired compartment.we  observed  the  changes  of  the  structure  of  the  synapses  of  neuronal  cells  in  the  right amygdala(the length of the active zones, thickness of the post-synaptic density (PSD),synaptic cleft width and curvature of the synaptic interface) by using a transmission electron microscopy. 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 A+EA groups were apparently decreased(P<0.05), and the time spent in the CPA-paired compartment was apparently increased in the EA group(P<0.05), suggesting a pain relief and an improvement of the negative affection mood after EA intervention. Additionally, In comparison with the normal group, the length of the active zones, thickness of PSD and the curvature of the synaptic interface were considerably decreased (P<0.001), and the synaptic cleft width was notably increased (P<0.001) in the model group. Compared with the model group, the length of the active zones and PSD thickness were significantly increased (P<0.001), and the synaptic cleft width was markedly decreased (P<0.01)in both the EA and AEA groups, the curvature of the synaptic interface was markedly increased in the EA group(P<0.05),and the curvature of the synaptic interface had no apparent changes (P>0.05),indicating an improvement of the synaptic plasticity changes of   neuronal cells in the amygdale following EA intervention.  Conclusion:  Repeated EA stimulation of ST 36-GB 34 has a role in relieving  both  sensory  and  affection  dimensions  of  chronic  pain  in  CNPPNA  rats,EA  can  remodel  the synaptic plasticity changes of neuronal cells in the Amygdala by reversing neuropathic pain plus negative affection induced decrease of the length of the active zones, PSD thickness and the curvature of the synaptic interface, and widening of the synaptic cleft .

Key  words:  Acupuncture  and  Moxibustion,  Electroacupuncture  analgesia;  Chronic  neuropathic  pain; Affection dimension; Sensory dimension; Amygdala;Synaptic plasticity-related proteins.