Amino acids as dietary excitotoxins: a contribution to understanding neurodegenerative disorders

The possibility that some acidic amino acids occurring naturally or as additives in the diet can act as excitotoxins producing central nervous system pathology has been the subject of extensive debate in the last 20 years and is here reviewed. High doses of glutamate, aspartate or related excitatory amino acids given in isolation to neonatal rodents produce acute degeneration organs. Neuropathology resulting from consumption of glutamate or aspartate has not been described in man. Various unusual amino acids of plant origin can produce acute excitotoxic syndromes. In man domoate (consumed in mussels that have fed on (Nitschia pungens) can produce an acute syndrome associated with limbic system lesions and anterograde amnesia. Kainate and domoate produce similar syndromes in rodents; acromelate produces spinal pathology. The mechanisms and manifestations of chronic excitotoxicity are less clearly established. A combination of impaired energy metabolism or impaired buffering of calcium and free radicals and endogenous or exogenous excitotoxins may contribute to neuronal loss in human neurodegenerative disorders.