Cortical and tectal afferent terminals in the suprageniculate nucleus of the cat.

The suprageniculate nucleus (Sg) of the cat was observed electron microscopically after wheat germ agglutinin-horseradish peroxidase (WGA-HRP) injection into the anterior ectosylvian visual cortical area (AEV) and superior colliculus (SC). Small axon terminals filled with round synaptic (RS) vesicles were labeled with HRP injected into the AEV and SC, whereas large axon terminals containing round synaptic (RL) vesicles were labeled after HRP injection in the SC. After producing a lesion in the AEV and adjoining orbito-insular cortex and injecting WGA-HRP into the SC, degenerated terminals and HRP-labeled RS terminals were occasionally found to make synaptic contacts with a single dendritic profile of Sg neurons.