Study On The Effects Of SP On The Modulation Of The NMDA And SP Auto-receptor

Part 1. The effects of SP on the behavior in capsaicin-induced pain in rats.Objective: In this study, we made the neuropathic pain model through injecting capsaicin around the dorsal thigh sciatic nerve in rats, then gave exogenous SP by intraperitoneal injection to explore the effects of SP on thermal hyperalgesia in capsaicin-induced pain in rats.Methods: To investigate these effects,48 SD rats were randomly divided into 6 groups: Group A: normal control group; Group B:capsaicin group; Group C: capsaicin 10-4 mol/L+SP 10-5 mol/L group; Group D: intraperitoneal injection of Capsaicin 10-4 mol/L+SP 10-4 mol/L injection; Group E: intraperitoneal injection of SP 10-3 mol/L + Capsaicin 10-4 mol/L injection; Group F: intraperitoneal injection of normal saline. Each group was done with hot-plate test with the duration of 10,20,30,40,50,60 min before and after experiment.Results:(1) The rats were significantly shortened after injection of capsaicin (P<0.05). (2) After SP was given in capsaicin-induced pain rats as an intervention, the rats were significantly shorter than the single injection of capsaicin (P<0.05).Conclusion: According to experimental results, SP may play a role in promoting nociceptive pain information in rats and resulting in hyperalgesia by combining its receptors.Part 2. The Expression of NMDA receptor and SP auto-receptor changes in dorsal root ganglion after capsaicin-induced pain in ratsObjective: Our study was to investigate whether SP was involved in the modulation of the primary sensory information. With immunohistochemical technique, we observed the expression of SP changes in dorsal root ganglion (DRG) and the corresponding segments of spinal cord after capsaicin-induced pain in rats.Methods: To investigate these effects,40 SD rats were randomly divided into 5 groups, Group A: normal control group; Group B:saline group; Group C:capsaicin 1 h group; Group D:capsaicin 6 h group; Group E: capsaicin 12 h group. Respectively given intraperitoneal anesthesia after 1 h,6 h,12 h,4% para formaldehyde (4℃) was perfused from ascending aorta to left ventricle to fix the sample, then dorsal root ganglia and spinal cord was removed to stripped slices, with immunohistochemistry, microscopy, computer image analysis.Results:(1) In saline group and capsaicin 1 h group, the positive expression rate of SP in DRG Neurons in Rats showed no difference (P>0.05), the gray value of NMDA positive neurons increased (P<0.05). Compared capsaicin 6 h group with capsaicin 1 h group, the positive expression rate of SP mediated DRG neurons obviously increased (p<0.05), and the gray value decreased (P<0.05). Between capsaicin 12 h group and capsaicin 12 h group, the positive expression rate neurons in DRG obviously increased (P<0.05), and the gray value decreased (P<0.05).(2) Compared capsaicin 12 h group with capsaicin 1 h group, the gray value of NMD A positive neurons in the spinal dorsal horn obviously decreased (P<0.05).Conclusion: According to the experimental results, Expression of SP is significantly up-regulated after capsaicin-induced pain in DRG neurons, which indicates that SP is involved in the modulation of nociceptive pain information transmission on the level of spinal cord.