Role of the interval between axotomy and nerve suture on the success of muscle reinnervation: an experimental study in the rabbit.

The influence of the time interval between nerve transection and neurorrhaphy on motor and sensory reinnervation was studied experimentally in the rabbit. We evaluated the maximal tetanic tension, the amplitude of the compound action potential, and the retrograde transport of horseradish peroxidase 30 and 60 days after neurorrhaphy carried out at 0, 10, or 20 days after transection of the nerves to the medial and lateral gastrocnemius and soleus muscles. The results showed that the suture 20 days after transection was followed by a more precocious motor reinnervation, whereas the outgrowth of motor axons past the suture was not affected by the time interval between transection and neurorrhaphy. On the contrary, the best regrowth of afferent axons was obtained after an interval of 10 days between transection and suture. We conclude that the time interval did not influence motor axon growth, but was involved in the operation of mechanism(s) involved in the reestablishment of impulse conduction and/or synaptic efficacy. In contrast, the time interval appeared to be related to factors involved directly in the axonal elongation of afferent fibers.