MONOAMINE-OXIDASE-A-POSITIVE RETINAL GANGLION-CELLS PROJECTING TO THESUPERIOR COLLICULUS AND DORSOLATERAL GENICULATE-NUCLEUS OF THE RAT-BRAIN

Detailed morphology and distribution of monoamine oxidase type A (MAO- A) positive retinal ganglion cells, and their synaptic terminals in th e superior colliculus and the lateral geniculate nucleus, were investi gated by light and electron microscopy. In addition, the differences i n various retinal ganglion cells with respect to the projection site w ere examined by the injection of colloidal gold into the superior coll iculus and the lateral geniculate nucleus. The effects of unilateral e nucleation were also examined. In the retina, small, medium and large sized MAO-A-positive ganglion cells were observed; the large sized cel ls were distributed evenly throughout the retina, while the small and medium sized cells were most numerous in a ring surrounding the centra l retina and decreased in density near the optic disc and the peripher al retina. The MAO-A-positive terminals in the superior colliculus wer e smaller in size than those in the lateral geniculate nucleus. From c olloidal gold injections, it was apparent that the MAO-A-positive gang lion cells projecting to the superior colliculus were generally smalle r in size than those projecting to the lateral geniculate nucleus. Fou rteen days after unilateral enucleation, the MAO-A-positive terminals in the superior colliculus and lateral geniculate nucleus contralatera l to the enucleated eye had almost disappeared, whereas those in the i psilateral regions remained unaffected. These findings demonstrate the distribution and projections of the MAO-A-positive ganglion cells. (C ) 1998 Academic Press Limited.