Figure 2.
Passive and carrier-mediated flux of cocaine at the mouse luminal BBB. A, Total flux (J in; nmol/sec/g; dashed line) measured in the right brain hemisphere of male Swiss mice and plotted against total cocaine concentration in the perfusion buffer (Krebs-carbonate) at pHe 7.40 (Equation 6). The straight dotted line represents the passive diffusion flux of cocaine (K passive of 4.5±1.0 µL/sec/g at pH 7.4). The solid line represents the curve obtained by subtracting the passive flux from the total flux and fitted to the carrier-mediated Michaelis-Menten term (see Equation 7) by nonlinear least-square regression. Estimated parameters for the brain transport of cocaine are: K m, 4.5±1.8mM; V max, 127.2±34.5 nmol/sec/g. Data represent means±SD of 4 to 5 mice. B, Total (dashed line), carrier-mediated (solid line), and passive (dotted line) cocaine fluxes at pharmacological concentrations at the mouse BBB, fitted according to Equation 7 for concentrations <0.1mM.