Figure 6. Effects of X-ray irradiation on muscle reinnervation after nerve crush or paralysis with botulinum toxin.

After nerve crush (A–C) reinnervation appeared fast and was nearly complete in both non-irradiated (^) and irradiated muscles (•) as indicated by similarity of contractile force evoked by nerve and direct electrical stimulation (degree of innervation, C) and decreasing sensitivity to bath-applied acetylcholine (B, ACh-induced contracture amplitude as a percentage of maximum tetanic force). Reinnervation after botulinum paralysis (D–F) remained insufficient throughout the period of observation as seen from the low degree of innervation (F) and high sensitivity to bath-applied acetylcholine (E) in irradiated (•) versus non-irradiated muscles (^). Note the persisting force deficit in irradiated muscles as compared with non-irradiated solei (A and D) and the reduced maximum force in non-irradiated botulinum-treated muscles compared with nerve crush without irradiation (A and D). Each point represents one muscle. The plotted curves are non-linear regression lines for irradiated (continuous lines) and non-irradiated muscles (dashed lines) fitted with SigmaPlot 5.0 software (SPSS Europe, Erkrath, Germany).