REINNERVATION ACCURACY OF THE RAT FEMORAL NERVE BY MOTOR AND SENSORY NEURONS

Previous studies in the rat femoral nerve have shown that regenerating motor neurons preferentially reinnervate a terminal nerve branch to m uscle as opposed to skin, a process that has been called preferential motor reinnervation. However, the ability of sensory afferent neurons to accurately reinnervate terminal nerve pathways has been controversi al. Within the dorsal root ganglia, sensory neurons projecting to musc le are interspersed with sensory neurons projecting to skin. Thus, ana tomical studies assessing the accuracy of sensory neuron regeneration have been hampered by the inability to reliably determine their origin al innervation status. A sensory neuron that regenerated an axon into a terminal nerve branch to muscle might represent either an appropriat e return of an original sensory afferent to muscle stretch receptors o r the inappropriate recruitment of a cutaneous sensory afferent that o riginally innervated skin. The current experiments used a labeling str ategy that effectively labels motor and sensory neurons projecting to a terminal nerve branch before experimental manipulation of the parent mixed nerve. Our results confirm previous observations concerning pre ferential motor reinnervation for motor neurons, and show for the firs t time anatomical evidence of specificity during regeneration of senso ry afferent projections to muscle. in addition, the accuracy of sensor y afferent regeneration was highly correlated with the accuracy of mot or regeneration. This suggests that these two distinct neuronal popula tions that project to muscle respond in parallel to specific guidance factors during the regeneration process.