Effects of the COMT inhibitor, CGP 28014, on plasma homovanillic acid and O-methylation of exogenous L-dopa in the rat.

Methods potentially suitable for the determination of the COMT inhibitory properties of CGP 28014 (N-(2-pyridone-6-yl)-N',N'-di-n-propylformamidine) in humans were tested in rats: the measurement of effects on HVA levels and on the conversion of exogenously administered L-DOPA into its O-methylated derivative, in serum and striatum. The compound decreased HVA as well as the conversion of L-DOPA to O-methyl-DOPA similarly in serum and striatum. The latter parameter was considered to be more useful for the assessment of COMT inhibition in humans, because it is less affected by diurnal changes, dietary effects, physical activity etc.