An analysis of the transport of WGA-HRP in the cat's visual system

The increasing use of WGA-HRP as a neuroanatomical tracer has led us to examine two aspects of its uptake and transport. Microelectrophoretic deposits of WGA-HRP were centered in lamina A of the LGd to determine whether or not there is a discrepancy between the size of the deposit site and the effective uptake zone. For this purpose, the size of the deposit site was compared to the area of labeled ganglion cells in the retina. It was found that the effective uptake zone is approximately one half the size of the geniculate area containing reaction-product. Deposits of WGA-HRP in the optic tract, optic radiations and corpus callosum were made in order to determine if this tracer is incorporated and transported by intact fibers. In no case were labeled axon terminals or neuronal somata observed. However, application of the conjugated enzyme to cut fibers of the corpus callosum resulted in robust labeling.