STUDY ON THE RECONSTRUCTION OF VISUAL PATHWAYS

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1. Studies on optic nerve regeneration in cats1) As a continuation of the previous study we recorded 260 visually responsive units from teased fibers of the sciatic nerve through which retinal ganglions cell axon regenerated. We confirmed the outnumber of Y cells than X and other cells and further found that among X cells there was no OFF center cell while in Y cells both ON and OFF were sampled. 2) After anterograde labeling with biocytin we studied the cross section of the regenerated optic axons and found that most of the axons were unmyelinated and the diameter range was smaller even among myelinated fibers as compared with the diameter range of normal optic axons in cats. 3) Morphological types of ganglions cells which survived for 2 months after optic nerve section were studied by a retrograde labeling method coupled with intracellular injections of Lucifer Yellow. alpha (Y)cells turned out to be the most resistant to axotomy over the other cells types.2. Functional recovery of v … More ision was studied in adult hamsters with a reconstructed retinocolliclar projection by the peripheral nerve transplant. In two hamsters out of four relative recovery of vision was obtained in avoidance score during the session of conditioned avoidance behavior using a light stimuli as a conditioning stimulus. For these two animals we succeed to trace regenerated retinal axons into the superior colliculus by an anterograde labeling with WGA-HRP. Furthermore we succeeded to obtain EEG desynchronization after photic stimulation into the eye which was bridged to the colliculus with a peripheral nerve graft.3. Effects of neurotrophic factors such BDNF, NT3, NT4 on axonal regeneration of retinal ganglion cells were studied 2-30 days after optic nerve section. Intracellular injections of neurobiotin revealed detailed morphology of regenerating axons such as recurring axons and side branches within the whole mount preparation. BDNF was found most effective to increase the number of recurring axons with occasional side branches. Less