Hoffman J M, Melega W P, Hawk T C, Grafton S C, Luxen A, Mahoney D K, Barrio J R, Huang S C, Mazziotta J C, Phelps M E
Department of Radiological Sciences, UCLA School of Medicine.
J Nucl Med. 1992 Aug;33(8):1472-7.
Carbidopa (L-alpha-hydrazino-alpha-methyl-b-(3,4-dihydroxyphenyl) propionic acid is a known inhibitor of aromatic amino acid decarboxylase. In both humans and monkeys, we studied the effects of carbidopa on plasma and brain kinetics of 6-[18F]fluoro-L-DOPA (FDOPA), an analog of L-DOPA used for PET studies of the central dopaminergic system. Pretreatment with carbidopa resulted in increases in the plasma levels of FDOPA and 3-O-methyl-6-[18F]fluoro-L-DOPA (3-OMFD). Total striatal and cerebellar activities measured with PET were also increased. Furthermore, increases observed in the specific striatal activity (striatum minus cerebellum total activity) were correlated with increases in the plasma FDOPA curve. Carbidopa pretreatment did not affect the influx rate constant (K) for FDOPA from plasma to striatum in humans as determined by Patlak graphical analysis. Thus, an increase in measured striatal tomographic activity was secondary to the increase in plasma FDOPA levels rather than as a result of changes in the FDOPA influx rate constant.
卡比多巴（L-α-肼基-α-甲基-β-（3,4-二羟基苯基）丙酸）是一种已知的芳香族氨基酸脱羧酶抑制剂。在人类和猴子身上，我们研究了卡比多巴对6-[18F]氟-L-多巴（FDOPA）的血浆和脑动力学的影响，FDOPA是L-多巴的类似物，用于中枢多巴胺能系统的PET研究。卡比多巴预处理导致FDOPA和3-O-甲基-6-[18F]氟-L-多巴（3-OMFD）的血浆水平升高。用PET测量的纹状体和小脑总活性也增加。此外，观察到的纹状体比活性增加（纹状体减去小脑总活性）与血浆FDOPA曲线的增加相关。根据Patlak图形分析，卡比多巴预处理不影响人类血浆中FDOPA流入纹状体的速率常数（K）。因此，测量到的纹状体断层活性增加是血浆FDOPA水平升高的继发结果，而不是FDOPA流入速率常数变化的结果。
