The characteristics and distribution pattem of
retinal afferent terminals making synaptic contacts on
narrow field vertical neurons in the stratum griseum
superficiale of the rabbit superior colliculus were studied
using the Golgi-gold substitution technique in
combination with either autoradiographic or
degenerative methods. At the level of light microscopy,
identified gold-toned vertical neurons showed similar
features to those previously described by others.
Although their axons were frequently seen rising from
the basal dendritic tuft, they could also emerge from an
apical dendrite, but rarely from the cell body. The
electron rnicroscopic study revealed that these neurons
received radiolabelled or degenerated profiles with
typical features of retinal terminals, while more proximal
parts seemed to receive fewer terminals but of larger
size. Axo-somatic synaptic junctions were very rare and,
interestingly, retinal terminals were not seen forming
synapses on the basal dendritic arborization. The present
results indicate that the narrow field vertical cells are
targets for retinotectal projection