FIGURE 2.

(−)-PA is endogenously produced in the brain. Mouse brain tissue, blood, and mouse food pellets were collected, freeze-dried, and subjected to UPLC/MS/MS as described under “Experimental Procedures.” PA, ABA, and its metabolites from mouse brain tissue (A), blood (A), and mouse food pellets (B) were quantitatively determined against DW. ** indicates statistical significance (p < 0.01 by paired t test; n = 4 for blood; n = 15 for brain tissues). Both (+)-ABA and (−)-ABA at a dose of 45 mg/kg each were injected into mouse veins. After 2 and 5 h, brains were collected to determine the level of PA and other ABA metabolites in the brain as shown in C. Error bars represent the mean ± S.E. ** indicates statistical significance (p < 0.01 by paired t test; n = 3).