Bennett and Xie (1988) described an experimental peripheral neuropathy that is produced by loosely ligating a rat's left sciatic nerve with chromic gut suture. Four ligations, which are tied tightly enough to constrict the nerve and retard epineurial blood flow, produce a chronic constriction injury (CCI). Maves et al. (1993) reported that if the ligations are tied more loosely (i.e., no retardation of blood flow) than those that produce the CCI, rats exhibit postural changes only when the ligations are of chromic gut. We decided to evaluate effects of different suture materials on the abnormalities in paw position associated with the CCI (Attal et al., 1990). Five groups of rats were included in this study. In three of the groups, the CCI was produced with chromic gut, plain gut, or polyglactin (Vicryl) suture. Rats in the fourth group served as sham injury control animals, and rats in the fifth group served as unoperated control animals. Our results indicate that the position in which the rats held the affected hindpaw varied significantly among treatment groups. Rats whose CCI was induced with chromic gut suture spent more time with the hindpaw in an abnormal position than rats in the other treatment groups. And as compared to rats in the unoperated control group, rats whose CCI was induced with either plain gut or polyglactin suture also spent more time with the hindpaw in an abnormal position. Though these different suture materials produced similar degrees of nerve constriction, the effects on paw position were greater with chromic gut suture. These results suggest that chromic gut suture, when used to produce the CCI, may have more than just a constrictive effect on the sciatic nerve. However, since all suture materials produced changes in paw position, constriction is likely to play an important role in the development of abnormalities in paw position observed in rats with the CCI.

No abstract

The chronic constriction injury (CCI) is an animal model of an experimental peripheral neuropathy. In this model, a mononeuropathy is produced by loosely ligating the left sciatic nerve of the rat with chromic gut suture (Bennett and Xie 1988). Maves et al. (1993) have proposed that chemical constituents of chromic gut suture influence the behavioral changes of rats with the CCI. Considering their results, we became interested in evaluating whether the type of suture material used to produce the CCI also affected spinal levels of calcitonin-gene-related peptide immunoreactivity (CGRP-ir) and substance P immunoreactivity (SP-ir), peptides that are associated with small primary afferent neurons. Using methods of radioimmunoassay (RIA), we measured levels of CGRP-ir and SP-ir in the dorsal quadrants of approximately the lumbar 4-5 (L4-L5) spinal segments of rats with a CCI induced using polyglactin (Vicryl), plain gut, or chromic gut suture. We observed bilateral decreases in CGRP-ir and SP-ir 60 days after a CCI induced with chromic gut suture, but no changes in peptide levels after a CCI induced with either polyglactin or plain gut suture. These results suggest two possibilities: (1) chromic gut suture, when used to produce the CCI, has more than just a constrictive effect on the sciatic nerve, and/or (2) different suture materials produce changes in CGRP-ir and SP-ir with a differential time-course. Our experiments are unable to distinguish between these two possibilities.