of Neuronal Connections in the Macaque Monkey

Abstract

Recently, an MRI-detectable, neuronal tract-tracing method in living animals was introduced that exploits the anterograde transport of manganese (Mn2? ). We present the results of experiments simultaneously tracing manganese chloride and wheat germ aggluti- nin conjugated to horseradish peroxidase (WGA-HRP) to evaluate the specificity of the former by tracing the neuronal connections of the basal ganglia of the monkey.Mn2? and WGA-HRPyielded remarkably simi- lar and highly specific projection patterns. By showing the sequential transport of Mn2? from striatum to pal- lidum-substantia nigra and then to thalamus, we dem- onstratedMRIvisualization of transport across at least one synapse in the CNS of the primate. Transsynaptic tract tracing in living primates will allow chronic stud- ies of development and plasticity and provide valuable anatomical information for fMRI and electrophysiolog- ical experiments in primates.