Table 2

DA uptake as a function of DA concentration at various cationic conditions

[Na⁺]	Substituted Cations	n	H_iCoefficient	K_[DA]	V_app
mM				μM	pmol/s/mg
155		8	1.04 ± 0.07	2.66 ± 0.18	37.2 ± 1.5
55	Li⁺	7	0.96 ± 0.07	4.95 ± 0.46^2-a	43.4 ± 1.7
	Choline	5	1.01 ± 0.02	6.24 ± 0.60^2-a	40.7 ± 1.8
	K⁺	7	0.92 ± 0.10	2.97 ± 0.16	13.9 ± 0.7^2-a

The DA concentration varied from 1 to 8 μM. The indicated Na⁺concentration was altered by replacing NaCl with isosmolar quantities of LiCl, choline chloride, or KCl. Shown are means ± SE ofn experiments.

↵2-a Dunnett’s test; p < .01 versus 155 mM Na⁺.