ABSTRACT
In the course of Parkinson's disease, massive degeneration of mesencephalic dopaminergic neurons occurs, in adults, over a period of several decades. Other neuronal populations, for example, the cholinergic neurons of the nucleus basalis of Meynert or the noradrenergic neurons of the locus coeruleus, may be affected as well, although to a lesser extent. It is not known why these neurons die, nor whether all the affected populations degenerate for the same reason. The following discussion will ignore the question of nondopaminergic neuronal degeneration, with the hope that once the mechanism underlying the death of the dopaminergic neurons is elucidated, the death of the others will also be explicable.
