Light-optic, electron microscopic and electrophysiological study of centrifugal fibers of the retina in the lamprey Lampetra fluviatilis

Light and electronmicroscopic studies have been made on retinal structures in the lamprey labeled by horseradish peroxidase injected into the peripheral end of the cut optic nerve or to the midbrain tectum. On total retinal preparations, labeled axons were revealed together with dendrites and ganglionic cell bodies, as well as branching (presumably retinopetal) fibers, fine endings of which come closely to the labeled dendrites of the ganglionic cells. Electron microscopic data indicate that the labeled terminations of afferent fibers from synapses with both labeled and unlabeled dendrites, as well as with unlabeled neuronal bodies. It is concluded that centrifugal fibers in lamprey retina form contacts with the bodies and dendrites of the amacrine cells and dendrites of the ganglionic cells. Results of intracellular registration of responses of various retinal elements to the electrical stimulation of the optic nerve support this conclusion.