N-METHYL-D-ASPARTATE (NMDA) RECEPTORS IN THE SPINAL-CORD AND MOTOR CORTEX IN MOTOR-NEURON DISEASE - A QUANTITATIVE AUTORADIOGRAPHIC STUDY USING [H-3] MK-8O1

The distribution and density of NMDA receptors in spinal cord and motor cortex was compared in motor neuron disease (MND; 10 cases) and controls (8 cases) using [H-3]MK-801 autoradiography. In the spinal ventral horn of MND cases, [H-3]MK-801 binding was reduced and there were fewer focal hot spots of binding. These changes are likely to reflect loss of motor neurons (MN) bearing NMDA receptors. [H-3]MK-801 binding was increased in intermediate spinal grey matter and deeper layers of the motor cortex in MND cases compared to controls. This may represent either an adaptive response to MN loss or a pathophysiological phenomenon contributing to MN degeneration.