Dopaminergic and cholinergic lesions in progressive supranuclear palsy

In 9 patients with progressive supranuclear palsy and in 27 controls, dopamine and homovanillic acid concentrations, choline acetyltransferase (CAT) activity, and the number of [3H]spiperone and [3H]quinuclidinyl benzilate binding sites were measured post mortem in the striatum (caudate nucleus, putamen, and nucleus accumbens), substantia innominata, and frontal cortex. Dopamine and homovanillic acid concentrations were reduced in the caudate nucleus and putamen but not in the nucleus accumbens or frontal cortex, indicating that the nigrostriatal dopaminergic system is lesioned in patients with progressive supranuclear palsy (as in those with Parkinson's disease) but not the mesocortical and mesolimbic dopaminergic systems, which are lesioned in parkinsonian patients. CAT activity and [3H]spiperone binding decreased in parallel fashion in all the structures. In the striatum, this suggests that the cholinergic neurons, which are target cells of the nigrostriatal system, also degenerate in this disease. This might explain the decrease in the number of dopamine receptors as well as the inefficacy of levodopa or anticholinergic therapy in these patients. The decrease in CAT activity in the substantia innominata and the frontal cortex indicates that the innominatocortical cholinergic system is lesioned in patients with progressive supranuclear palsy and may play a role in the intellectual deterioration observed. This lesion is also found in demented patients with Alzheimer's and Parkinson's diseases.