Light labeling of red nucleus neurons following an injection of peroxidase-conjugated wheat germ agglutinin into the inferior olivary nucleus of the rat.

Since the rubro-olivary projection has not been demonstrated in the rat, unlike the monkey and cat (refs. in text). HRP or highly-concentrated wheat germ agglutinin-horseradish peroxidase (WGA-HRP) was injected into the inferior olivary nucleus using a ventral approach. After processing with a modified technique, sections were examined under high power. Three rats injected with WGA-HRP showed labelling in the red nucleus. In one of those rats with a well-confined injection, 583 neurons contained grains of HRP reaction product consistent with light retrograde labeling. This observation lends support to the existence of a rubro-olivary projection in the rat.