The quantitative autoradiographic distribution of [ 3H]MK-801 binding sites in the normal human brainstem in relation to motor neuron disease

The distribution of N-methyl- d-aspartate (NMDA) receptors in the normal human brainstem has been investigated using MK-801. Specific [ 3H]MK-801 binding showed a heterogeneous distribution, the greatest density of binding sites being found in the substantia nigra, locus coeruleus, and the hypoglossal and inferior olivary nuclei. Brainstem motor nuclei subserving eye movements, which tend to be spared in motor neuron disease (MND), had significantly lower densities of binding compared to other cranial nerve motor nuclei (V, VII, X, XII) which tend to be affected. The anatomical distribution of NMDA receptors may be one factor determining selective vulnerability to excitotoxic injury.