Maximal rates of dopamine (DA) uptake (Vmax) are positively correlated with the app. Km of psychostimulants at the dopamine transporter
(DAT). DAT
transgenic overexpressing mice (A, DAT-tg) and rats that had undergone
MPH self-administration (B) were used to determine the effects of
increased DAT on the app. Km of psychostimulants.
Correlational analysis was run to compare the predrug measure of Vmax with the app. Km (app. Km) of dopamine uptake inhibition for methylphenidate (MPH;
red; 30 μM; MPH, n = 11; DAT-tg, n = 10), amphetamine (AMPH; green; 10 μM; MPH, n = 9; DAT-tg, n = 9) and cocaine (blue; 30 μM;
MPH, n = 9; DAT-tg, n = 9). Regression
lines of AMPH, MPH, and cocaine were compared to determine if the
range over which increases in Vmax increased
app. Km was similar. The extent to which
increased Vmax augmented app. Km was different between MPH and AMPH as compared
to cocaine. ***p < 0.001.