Neuropeptides in aging and dementia.

Although senile dementia of the Alzheimer's type (SDAT) is a common disease associated with advancing age, recent studies have suggested that SDAT should not be considered synonymous with old age but a disease process separate from normal aging. This study examined the morphology of two neurochemically-defined neuronal populations (i.e., neurophysin, somatostatin) in the cortex and hypothalamus to determine if structural changes in these neuropeptide systems associated with advancing age are similar to those seen with SDAT. Our findings suggest that morphological changes consistent with neuronal degeneration occur in somatostatin but not neurophysin-containing neurons in cases diagnosed to have SDAT, and these structural changes are different from those seen in aged brain without central nervous system disease. These data support the concept that senile dementia of the Alzheimer's type is not a single neurochemical related disease, but may be associated with anatomical lesions and biochemical imbalances among a number of neuropeptide and neurotransmitter systems.