Dopaminergic neurotransmitter systems in Alzheimer's disease and in Down's syndrome at middle age.

In 15 patients with Alzheimer's disease and in 10 with Down's syndrome at middle age, there was severe atrophy, neurofibrillary degeneration and loss of pigmented dopaminergic nerve cells from ventral tegmental area (A10) whereas nerve cells in neighbouring substantia nigra (A9) were much less affected in all three respects. It is suggested that these findings may represent different patterns of damage within the two systems in these conditions which may relate to the presence of Alzheimer type changes (senile plaques) within their respective projection fields.