PROJECTIONS FROM AND TO THE SUPERIOR COLLICULUS IN THE NUCLEUS OF THEOPTIC TRACT COMBINED WITH POSTEMBEDDING GABA IMMUNOCYTOCHEMISTRY IN THE RABBIT

The reciprocal connection between the nucleus of the optic tract and t he superior colliculus has been described for several species. In both nuclei GABA is an important transmitter and recently it has been show n that GABA plays a significant role in this connection. To investigat e this reciprocal connection at the ultrastructural level in the rabbi t, anterograde and retrograde tracers were injected in the superior co lliculus. Ultrathin sections were incubated with anti-GABA to elucidat e the presence of GABA in retrogradely labeled neurons or anterogradel y labeled terminals in the nucleus of the optic tract. The present res ults show that GABA is present in several neurons projecting from the nucleus of the optic tract to the superior colliculus and that all neu rons involved in this projections are contacted by GABA immunopositive terminals, In the projection from the superior colliculus to the nucl eus of the optic tract GABA play a less significant role.