Four-centimeter peripheral nerve allografts were inserted into gaps in the sciatic nerve of 42 Wistar rats. Twenty-one rats were treated with azathioprine (Imuran) during the regeneration period, and 21 rats were control animals. Regeneration through the grafts was assessed by clinical, electrophysiological, and histological means.
At six months postoperatively, the mean motor conduction velocity in the grafted nerves and the amplitude of the action potential of reinnervated muscles were significantly greater in the treated animals than in the controls. There was also a greater density of myelinated fibers in the graft and distal nerve segments of the treated animals than in those of the controls. Suspension of immunosuppressive agents after regeneration had occurred did not result in deterioration of nerve function. It is concluded that immunosuppressive agents aid regeneration through peripheral nerve allografts.