[Pathology of catecholaminergic innervation of the cerebral cortex in Alzheimer's dementia].

Changes in cerebral catecholaminergic pathways in Alzheimer type dementia would appear to involve both the noradrenergic and the dopaminergic system in their sub-cortical and cortical distribution, but the essential information currently available involves the noradrenergic innervation of the cerebral cortex. Involvement of this system was first detected by the authors using fluorescence histochemistry on biopsy specimens. In addition to the notable decrease in noradrenergic axons, three types of changes were seen: irregular axonal swelling with neurotransmitter diffusion phenomena, appearances of axonal interruption and, specific to the three cases of pre-senile form of Alzheimer's disease which were studied, the presence of large spherical or fusiform dilatations on the axonal endings, close to senile plaques. Thus histochemical study indicates the possibility of complex involvement, not only of synthesis of the neurotransmitter, but probably also of other properties of the noradrenergic axons: axonal flow, membrane permeability and hence, possibly liberation, uptake and storage of the mediator. These histochemical findings have been confirmed by other teams, who have demonstrated a neuronal loss of 20 to 80% in the locus coeruleus, a nucleus providing the cortical noradrenergic bundle. In addition, biochemical estimations have revealed either a severe reduction of the order of 90% in endogenous noradrenaline (3 personal cases), or a fall of 20 to 45% (cases from the literature), in relation with the method of biopsy or autopsy specimen and the form of pre-senile or senile dementia.(ABSTRACT TRUNCATED AT 250 WORDS)