Increased binding of 3H-L-deprenyl in spinal cords from patients with amyotrophic lateral sclerosis as demonstrated by autoradiography.

The present investigation has applied quantitative autoradiography and histochemistry to study the regional distribution of MAO-B and its relation to the number of cells in respective regions. L-deprenyl binds irreversibly and quantitatively to the B-form of monoamine oxidase, MAO, and is an ideal 3H-ligand to measure the MAO-B enzyme protein in tissues by means of in vitro autoradiography. The investigation is performed on spinal sections from five controls and five cases with amyotrophic lateral sclerosis (ALS) on cervical, thoracic and lumbar level. The highest density of 3H-L-deprenyl binding was found around the central canal (lamina X). MAO-B was markedly increased (up to 2.5 times of values in controls) specifically in regions of neurodegeneration e.g. motor neuron laminae and corticospinal tracts. There was a high correlation between glial cell count and 3H-L-deprenyl binding with a relation indicating enhanced MAO-B protein in glial cells within areas of neurodegeneration. In contrast the increased microglial cell number in ALS did not show any correlation with 3H-L-deprenyl binding.