REINNERVATION OF MUSCLE IN THE MOUSE FOLLOWING NERVE CRUSH AND X-IRRADIATION

¹ Department of Neuropathology, Institute of Neurology, The National Hospital, Queen Square, London WCIN 3BG

The effects of X-irradiation on nerve regeneration were examined in adult mice. The right sciatic nerve was crushed focally and 3 d later the hind limb was exposed to 20 Gy X-rays. Compound muscle action potentials (m.a.p.s) were recorded in vivo from the posterior crural muscles. Stimulation of the sciatic nerve proximal to the crush injury evoked m.a.p. s of low amplitude with marked temporal dispersion. Stimulation at 20 or 50 Hz resulted in almost immediate intermittent failure of the longer latency m.a.p.s. In vitro physiological examination showed X-irradiation to have no effect on the timing of reinnervation. However, the latency of evoked end-plate potentials was prolonged and, on repetitive nerve stimulation, increased markedly until failure occurred. Nerves which regenerated after X-irradiation showed impaired conduction, particularly of trains of impulses.