Real-time PCR of PhT1 transcripts (A) and immunoblots of PhT1 protein expression (B) in the cerebral cortex, cerebellum and hippocampus of rat brain from day 2 (D2) to week 8 (Adult), and effect of potential inhibitors, GlySar and histidine (L-His), on the uptake of 2 µM [14C]GlySar in brain slices prepared from the hippocampus of adult (C) and neonatal (D) rat brain. Similar functional results were obtained in the cerebral cortex and cerebellum of rats (data not shown). Values are mean ± SE (n=6). *p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001 as compared to adult (panel A) and control (panels C and D) animals.