Long term regeneration of contralateral and induced ipsilateral retinal projections to the remaining optic tectum of Rutilus rutilus

The regeneration of optic tract fibers has been investigated in Rutilus kept at 18–20°C, 6–7 months after ablation of one optic tectum and simultaneous section of the optic nerve from the contralateral eye. The labeling of the optic fibers obtained following injection of either tritiated proline or HRP in either of the eyes showed the existence of a normal contralateral retino-tectal projection to strata opticum, fibrosum et griseum superficiale (SFGS), griseum centrale, and album centrale. Furthermore, it demonstrated the presence of a conspicuous newly-formed ipsilateral retino—tectal projection to both superficial and deep layers of SFGS in the form of horizontal bands. The partial overlapping of ipsi- and contralateral projections in SFGS was confirmed by a double-labeling technique (HRP and tritiated proline). The results suggest a retinal hyperinnervation of the remaining optic tectum.