Effects Of Intrathecal Sufentanil And Protein Kinase C Inhibitor On Rat's Pain Threshold And Changes Of Neuronal NMDA Receptor And CGRP Expression In Rat Spinal Dorsal Horn Following Spared Nerve Injury Of Sciatic Nerve

Objective: The present study was initiated to observe the effect of intrathecal sufentanil and protein kinase C inhibitor on rat's pain threshold and changes of nervronal N-methyl-D-aspartate recaptors (NMDAR) and Calcitonin gene-related peptide (CGRP) expression in rat spinal dorsal horn following spared nerve injury of sciatic nerve by using immunohistochemistry method.Methods: fifty-four healthy male Sprague-Dawley rats (220-280g) were randomly devided into six groups(n=9): control group(group C) weren't operative procedure, sham group (group sham) involved exposure of the sciatic nerve and its branches without any lesion. spared nerve injury model group (group SNI),sufentanil group (group Suf),Chelerythrine Chloride which is protein kinase C inhibitor group (group P) and sufentanil+protein kinase C inhibitor group(group SP) which received a lesion of two of the three terminal branchesof the sciatic nerve(tibial and common peroneal nerves) leaving the remaining sural nerve intact (spared nerve injury model, SNI). These rats in group Suf,group SP and group P were intrathecally injected 10μl sufentanil(1μg),sufentanil(1μg) and Chelerythrine Chloride (11μg),Chelerythrine Chloride (11μg) followed by 10μl normal saline 1 time every day duration 14 days after post-surgery, respectively.Similarly, rats of group C, group sham and group SNI were intrathecally injected 20μl normal saline in uniform interval. Mechanical allodynia and radiogenic heat pain thresholds were measured on day 1 pre-surgery and on day 1, 2, 7, 14 post-surgery after intrathecally injection. On day 2, 7, 14 post-surgery 2 hours after intrathecally injection, the rats were killed in batch (3 rats/batch), and the L₅ spinal cord were dissected for determination of the expression of NMDAR and CGRP using immunohistochemical techniques.Result: (1) In group C and group sham, there were no difference on the statistics in pain threshold (P＞0.05); (2) There were significant difference on the statistics in pain threshold in group SNI as comparede with that in group C and group sham (P＜0.01) on days 14 post-surgery, but the radiant heat stimulus paw withdrawal latency was no change in SNI group comparede with that in group C and group sham (P＞0.05); (3) In group Suf and group P, there was significant difference on the statistics in pain threshold on days 1,2 post-surgery when compared to group SNI levels (P＜0.01), the radiant heat stimulus paw withdrawal latency was also noticeable prolonged (P＜0.01), pain threshold of two groups kept no change on 14 days post-surgery; Pain threshold was significantly raised in group SP than that in Group Suf(P＜0.05); (4) The expression of NMDAR and CGRP immunoreactive soma in the superficial laminae of the L₅ spinal dorsal horn was significantly increased in group SNI than that in group C and group sham (P＜0.01). (5)The expression of NMDAR and CGRP immunoreactive soma in group Suf and group P decreased significantly on days 2,7,14 post-surgery compared with that in group SNI, and there was also difference among group Suf and group P(P＜0.05), The expression of NMDAR and CGRP immunoreactive soma were significantly depressed in group group SP than that in Group Suf(P＜0.05).Conclusions: (1) Hyperpathia may be caused in the injured side limbs of rats following spared nerve injury of sciatic nerve. Intrathecal administration of sufentanil and protein kinase C inhibitor provide significant antinociception in the rat of SNI model; (2)The pain of SNI model can produced the increase of neuronal NMDAR and CGRP expression in rat spinal dorsal horn; (3) Intrathecal sufentanil and protein kinase C inhibitor significantly inhibited the increase of NMDAR and CGRP expression in rat spinal dorsal horn of SNI model, suggested the inhibition of NMDAR and CGRP pathway is one of the mechanisms for intrathecal sufentanil and protein kinase C inhibitor antinociception.