Relative importance of basement membrane and soluble growth factors in delayed and immediate regeneration of rat sciatic nerve.

Sciatic nerve regeneration was studied in two groups of rats. In group I, nerves were transected and transplanted immediately to the contralateral side. In group II, nerves were transected and transplanted 30 days later to the contralateral side. At 4 weeks, group II had an average nerve action potential amplitude of 784 +/- 292 microV and 43.2% +/- 6.7% of myelinated fibers were > 4 microns in diameter. In comparison, the respective measurements were 94 +/- 35.6 microV (p = 0.05) and 29.5% +/- 1.9% (p = 0.04) in group I. At 8 weeks, there were no significant differences in these measurements between groups. These data suggest that the environment in the distal stump improves early regeneration of nerve fibers when that stump was transected 30 days earlier. These and previous findings suggest that soluble trophic factors may be important in initiation of axonal regeneration.