analysis of unidirectional influx of blood-borne leu-enkephalin into the brain revealed michaelis-menten saturation kinetics in the parietal cortex , caudate nucleus , and hippocampus , with vmax between 0.14 and 0.16 nmol min-1 g-1 and km ranging from 34 to 41 microm , for the saturable component , whereas the estimated diffusion constant , kd , was not significantly different from zero .
C0006104
brain
C0007461
caudate nucleus