Ultrastructural evidence in mice that transganglionically transported horseradish peroxidase-wheat germ agglutinin conjugate reaches the intraspinal terminations of sensory neurons

Horseradish peroxidase conjugated to wheat germ agglutinin (HRP-WGA) has been localized by electron microscopy in the central projections of primary sensory neurons following injection of the tracer into the gastrocnemius muscle of mice. The tracer was taken up by nerve terminals in the muscle and transported transganglionically into the central spinal cord terminations of the primary sensory neurons. The HRP-WGA was localized using a new tetramethylbenzidine ultracytochemical method and the diaminobenzidine-glucose oxidase technique. The results demonstrate that the HRP-WGA is transported into the axon terminals after passing through the sensory ganglion. These data provide an experimental basis for the use of the conjugate to map the central projections of sensory neurons.