Degeneration of noradrenergic and serotonergic but not dopaminergic neurones in the lumbar spinal cord of parkinsonian patients

To investigate the possible alterations of spinal cord monoaminergic pathways in Parkinson's disease, the levels of dopamine, homovanillic acid, noradrenaline, serotonin and 5-hydroxyindoleacetic acid have been measured in different subregions of the lumbar spinal cord in control subjects and parkinsonian patients. Substantial amounts of these compounds were found in the dorsal, intermediate and ventral grey matter portions and in the white matter of the spinal cord; the levels of serotonin and its metabolite being the highest. In parkinsonian patients, lumbar spinal cord dopamine and homovanillic acid levels were similar to those in the control subjects, whereas the concentrations of noradrenaline, serotonin and its metabolites were clearly subnormal in the different parts of the cord, the depletion of noradrenaline being the most pronounced. These data suggest that lumbar spinal cord noradrenergic and serotonergic, but not dopaminergic, systems are damaged in Parkinson's disease.