Electrophysiological study of conditioning lesion effects on rat sciatic nerve regeneration following either prior section or freeze. II. Blocking by prior tenotomy.

The conditioning lesion effects refer to the earlier formation and the accelerated regeneration of axonal sprouts following two successive axotomies. In a previous study, we observed that a prior freeze or a prior cut of rat sciatic nerve resulted in differences in the enhancement of the regeneration rate and the reduction of the initial delay. These differences were interpreted as a possible non-neuronal cells influence on the intrinsic regulation of the conditioning lesion phenomenon. In the present study, we attempted to modify the status of the muscles using tenotomy before the prior nerve injury to determine the respective influence of the muscular cells on conditioning lesion effects. Thus, the conditioning lesion, which was either a cut or a freeze of the tibial nerve at the ankle, was performed 14 days after foot sole muscles were tenotomized, close to their insertion into the calcaneus bone. The test lesion was always a freeze of the sciatic nerve at midthigh performed 7 days following the prior lesion. The elongation of the regenerating sprouts was electrophysiologically evaluated and the regeneration rate as well as the initial delay were calculated by means of regression analysis. Tenotomy did not influence the regeneration as was demonstrated in a group with a single sciatic nerve lesion. In contrast, when prior lesion was performed, the tenotomy prevented both the enhancement of the rate of regeneration and the reduction of the initial delay, whatever was the type of the conditioning lesion.(ABSTRACT TRUNCATED AT 250 WORDS)