INFLUENCE OF THE DELAY OF DENERVATION ON SLOW STRIATED-MUSCLE RESISTANCE TO SLOW-TO-FAST CONVERSION FOLLOWING CROSS-INNERVATION

Cross-reinnervation, in cases of nerve repair or nerve transfer, can b e the consequence of wrong connections which are surgically induced be tween the different types of motoneurons (fast and slow). A slow muscl e nerve is able to convert a fast muscle virtually completely to the s low fibre type, whereas a fast muscle nerve exerts an incomplete contr ol over the properties of a slow muscle. Our experiments show that fol lowing delayed cross-reinnervation, a statistically significant slow-t o-fast transformation of the soleus muscle was observed, with a maximu m when nerve repair was performed 6 weeks following nerve section in t he rat model. Thus, the negative consequences on nerve and muscle rela tionship due to cross-reinnervation in the case of wrong connections b etween slow and fast motoneurons after conventional nerve suture or in the case of nerve transfer could be minimised by imposing a delay bef ore nerve repair. (C) 1996 Wiley-Liss, Inc.