TABLE 3.

Effect of d-amphetamine on [³H]MPP⁺ efflux [³H]MPP⁺ efflux experiments were conducted as described under Materials and Methods. The data of three (12.5, 25, and 50 nM d-Amph) or 10 (100 nM d-Amph) independent experiments were pooled and fit to one- and two-component dissociation experiments using MLAB-PC. The parameter values are ± S.D. In all cases, the two-component model fit significantly better than the one-component model (F-test, P < 0.002).

Condition	K1	A1	K2	A2
	min–1	%	min–1	%
d-Amph,† 12.5 nM	0.021 ± 0.005	57 ± 11*	0.18 ± 0.07	46 ± 10*
d-Amph,† 25 nM	0.015 ± 0.010	26 ± 1*	0.12 ± 0.03	70 ± 13*
d-Amph,† 50 nM	0.020 ± 0.010	19 ± 11*	0.15 ± 0.03	77 ± 10*
d-Amph, 100 nM	0.027 ± 0.010	22 ± 6	0.19 ± 0.02	88 ± 5

^*The A values of the curve (constraint 4; see Materials and Methods) were significantly different (F test, P < 0.01) from the 100 nM d-Amph curve. The kinetic constants of each curve did not significantly differ from those of the 100 nM d-Amph curve

^†The entire curve (constraint 1; see Materials and Methods) was significantly different (F-test, P < 0.01) from the 100 nM d-Amph curve