Reduction in [3H]glutamate binding in the visual cortex after unilateral orbital enucleation

Glutamate is a major neurotransmitter in the rat visual system. The effect of lesion-induced functional deficit on [3H]glutamate binding sites within anatomical components of the visual pathway has been examined using quantitative autoradiography. In the same animals, the magnitude and extent of the functional deficit was assessed with quantitative [14C]-2-deoxyglucose autoradiography. At 24 h after orbital enucleation, significant reductions (approx. 25%) in glutamate binding were present throughout the visual cortex but there were no significant alterations in glutamate binding in the two principal projections of the retina, the superior colliculus or lateral geniculate body. Function-related glucose use was significantly reduced throughout the visual pathway after orbital enucleation. Thus, alterations in the number of glutamate binding sites occur in some, but not all, of the regions in a polysynaptic pathway in which activity is altered.