Free D-aspartate and D-alanine in normal and Alzheimer brain.

In this report we present evidence for the presence of free D-aspartic acid (D-Asp) and D-alanine (D-Ala) in the white and gray matter of normal human brains and brains of individuals with Alzheimer's disease. D-Asp occurs at about the same concentration in the gray matter of both normal (18.6 nmol/g) and Alzheimer (14.8 nmol/g) brains, whereas in white matter its concentration is more than two times higher in normal than Alzheimer brains (22.4 and 10.5 nmol/g, respectively). D-Ala occurs in white matter at approximately the same concentration in both normal and Alzheimer brains (12.3 and 13.8 nmol/g, respectively), whereas in Alzheimer gray matter the D-Ala concentration is more than twice that found in normal gray matter (20.8 and 9.5 nmol/g, respectively). However, when the results are expressed as a percentage of D-amino acid/D+L, only small differences occur in all tissues examined.