Abstract
Selective neuronal degeneration with concomitant changes in neurotransmitter systems are features of both normal ageing and Alzheimer's disease. There are, however, important neurochemical differences in cerebral cortex. Choline acetyltransferase declines with age in frontal cortex in contrast to the prominent change in the temporal cortex in Alzheimer's disease. The loss of somatostatin, and the recently reported reciprocal change in corticotropin-releasing factor and receptors are not seen with ageing. However, age itself may have an important influence on the neurochemical deficits in Alzheimer's disease which are restricted in the older patients. The problems of post-mortem studies in the analysis of ageing and possible approaches to this are discussed.