Typical HPLC analysis of D-Asp and other amino acids from rat pituitary gland. Panel A, HPLC profile of amino acids from a standard mixture consisting of 50 pmoles of D-Asp and 100 pmoles of various L-amino acids. Panel B is the HPLC analysis of the same amino a cids, but after treatment with D-AspO. Panel C shows the HPLC analysis of free amino acids from 0.05 mg of rat hippocampus, and panel D is the same sample, but after treatment with D-AspO. The peak of D-Asp disappeared completely after incubation of the sample with D-AspO (panels B and D), indicating that the peak area of D-Asp was completely due to D-Asp.