Ammonia is endogenously generated in the brain in the presence of presumed and verified dementia of Alzheimer type

Abstract

The healthy, mature, non-starved brain was found to take up a small amount of ammonia on average 7.22 ± 0.72 μ g 100 g × min . In contrast, in patients thought to be suffering from incipient early-onset dementia of the Alzheimer type (DAT) the brain released a larger amount of ammonia on average 25.59 ± 16.17 μ g 100 g × min . In advanced DAT states, an average of 2.73 ± 0.32 μ g 100 g × min was released indicating the temporary nature of the severe loss of amino-N during the early stages of presumed DAT. Detrimental effects of endogenously formed ammonia on brain metabolism may affect the membrane potential, the excitability of neurons, and the energy metabolism. Ammonia may be assumed to be involved in the morphological changes in astrocytes and in the gliosis observed in early degeneration related to DAT. Endogenously generated brain ammonia thus may have a role in the cascade of cell damaging events in presumed incipient DAT.