Motor and sensory neurons of the rat sural nerve: a horseradish peroxidase study

Neurons of origin of the rat sural nerve were labelled with horseradish peroxidase. Dorsal root ganglionic cells were located in the L4 and L5 ganglia, and occasionally at the L6 level. Most of these sensory neurons measured under 35 microns in diameter. In keeping with previous electrophysiological studies suggesting the presence of motor fibers to plantar muscles in the rat sural nerve, motoneurons were identified at the caudal end of the L5 spinal segment, intermingled in the posterior aspect of the ventral horn with posterior tibial motor cells supplying the foot muscles. A quantitative analysis of HRP-labelled motoneurons revealed no difference between normal (average 67) and deafferented animals (average 70), the values being only marginally lower than counts of motor axons in deafferented sural nerves (average 80).