Brain damage in mice from voluntary ingestion of glutamate and aspartate.

Previous studies have shown that the putative excitatory neurotransmitters and neurotoxins, glutamate (Glu) and aspartate (Asp), destroy neurons in the brains of various animal species when administered orally by feeding tube. It has been argued, however that Glu and Asp are safe for human use as food additives since tube feeding is not a natural means of oral intake and efforts to demonstrate the brain damage in animals from voluntary ingestion of Glu or Asp have yielded negative results thus far. Here we demonstrate that weanling mice will voluntarily ingest large enough volumes of aqueous solutions containing Glu or Asp (or both) to sustain conspicuous hypothalamic damage. Certain deficiencies in the design of prior voluntary intake studies may explain the failure of others to demonstrate brain damage from voluntary ingestion of these excitatory neurotoxins.