NEUROTIZATION OF THE RAT SOLEUS MUSCLE - A QUANTITATIVE-ANALYSIS OF REINNERVATION

Neurotization-reinnervation of muscle by direct nerve implantation-has been the subject of several reports. The underlying neurobiology, how ever, has not been adequately studied. The use of a combined silver-ac etylcholinesterase stain was used in this study to identify reinnervat ed motor endplates and to quantify motor endplates reinnervated by the neurotization process. This study examined the effect of distance bet ween nerve implantation and native motor endplate zone on the formatio n of ectopic motor endplates and on the total number of motor endplate s reinnervated. Experiments were performed on the rat so(eus muscle. T he transected tibial nerve was implanted directly into the motor endpl ate zone (near, n = 10) or distally, far from the motor endplate zone (far, n = 10). After a reinnervation interval, frozen sections were pr ocessed to demonstrate both axons and motor endplates. In the near gro up, a mean of 566 motor endplates were reinnervated in the native moto r endplate zone and a mean of only 13 in distant locations. in the far group, a mean of 362 motor endplates were reinnervated In the native zone, while a mean of 477 were reinnervated in distant locations. Sign ificantly more Ectopic motor endplates were generated by far implantat ion, and native motor endplates were increased by near implantation. T he total number of motor endplates was independent of implant location . These experiments demonstrate that the distance between implanted ne rve and the native motor endplate zone influences the morphology of re innervation.