This study was carried out to compare electrophysiologically the efficacy of autogenous vein grafts, with autogenous nerve grafts as conduits for nerve regeneration. A 0.75-cm segment of sciatic nerve was resected in two groups of Sprague-Dawley rats of equivalent maturity. The nerve gaps were bridged with an autogenous vein graft in the first group (31 rats), and an autogenous nerve graft in the second group (24 rats). Serial in vivo nerve conduction velocity studies and terminal in vitro nerve conduction velocity and nerve action potential measurements were performed. An additional group of 21 animals who had undergone no surgical procedures, were similarly studied to establish an age-adjusted baseline for comparison. Twelve animals in the first group, 14 in the second group, and 13 in the baseline group survived the full year of study. In vivo conduction velocities between the two experimental groups compared favorably. Nerve conduction velocity determined by in vitro technique confirmed this finding and measured similarly at about 78 percent of the baseline. Nerve action potential amplitude in the vein-grafted group was 12.0 percent of the baseline, while the nerve-grafted group was 23.9 percent of the baseline. This study demonstrated that the vein graft compares well with the nerve graft in nerve conduction velocity, but only one-half as well in nerve action potential.

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A model was designed to evaluate the long-term in vivo electrophysiology of rat peripheral nerve transplants. The application of this model was demonstrated using cyclosporin (CSA) immunosuppression of recipient animals to facilitate peripheral nerve regeneration through nerve allografts. Isogenic Brown Norway (BN) rats [RT1n] were divided into three groups: two received Lewis (LE) rat [RT1l] allografts and one received BN isografts. One allograft recipient group received CSA immunosuppression for the duration of the investigation (150 days). Successful nerve regeneration in the isograft and the immunosuppressed allograft recipient groups was determined by immunohistochemical methods and serial in vivo electrophysiologic techniques to measure nerve conduction velocity and evoked compound muscle action potential amplitude. Statistical analysis of these results indicate that: (a) CSA immunosuppression of peripheral nerve allograft recipients facilitates peripheral nerve regeneration which is indistinguishable from isograft recipient controls at the functioning axon level; and (b) in vivo electrophysiologic monitoring in this model is particularly useful for long term peripheral nerve transplantation studies permitting serial assessment of regeneration with little morbidity.

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