Strain differences in peripheral-nerve regeneration in rats.

Currently, several strains of rats are used for studies of peripheral-nerve injury and repair. The purpose of this study was to determine if significant differences in regeneration between strains exist that might influence comparison of results and interpretation of scientific conclusions. One outbred (Sprague-Dawley) and four inbred stains (ACI, Wistar-Furth, Lewis, Brown-Norway) were studied. Animals were randomized to one of two experimental conditions, undergoing either posterior tibial nerve transection and repair, or Silastic conduit repair of the posterior tibial nerve (n=6/group). Endpoint evaluations at 6 and 13 weeks included histomorphometry and walking-track analysis. Evidence of excellent regeneration was noted in all rat strains undergoing primary repair. Generally, no statistically significant differences between strains were noted, regardless of endpoint evaluation used in the primary repair group. Nerve regeneration across the conduits was either poor or not present at 6 weeks, with no regeneration at all noted in any animals in the ACI and Brown-Norway groups, and regeneration in only one or two animals in the other strains. At 13 weeks, between three and five animals in each strain showed regeneration, but functional recovery was poor. Overall, few differences in peripheral-nerve recovery appear to exist between rat strains. It seems that uniform conclusions may be drawn regardless of strain used.

Peripheral nerve injection injury with antiemetic agents.

Antiemetics are widely used drugs, frequently administered to alleviate postoperative and postchemotherapeutic nausea and vomiting. While antiemetics do not induce peripheral neurotoxicity when administered systemically, it is not known whether peripheral nerve injury can occur as a result of inadvertent intraneural injection during intramuscular administration. The purpose of this study was to characterize the neurotoxic effect of three commonly used antiemetic agents (promethazine, dimenhydrinate, and prochlorperazine) as compared to saline in the rat sciatic nerve model. Intrafascicular and extrafascicular injection as well as direct application of the antiemetic drugs were performed. Nerves were harvested at 2 weeks postoperatively for histology and morphometry, with an additional sacrifice point at 8 weeks for the intrafascicular injection group. Injection injuries caused by antiemetic drugs differed depending on the agent injected and the location of injection. Extrafascicular injection and direct application caused no damage. Intrafascicular injection caused diffuse axonal injury in the promethazine and dimenhydrinate groups, while prochlorperazine caused only focal injury. Regeneration was prominent at 8 weeks in all intrafascicular injection groups in this rat model. Prochlorperazine thus appears to be less neurotoxic when injected intraneurally and should preferentially be used for intramuscular injections.