Figure 4. Competition studies on the norepinephrine (NET)(A), dopamine (B), and serotonin (SERT)(C) transporter cells. Human embryonic kidney (HEK)-NET, HEK-DAT, and HEK-SERT cells were incubated with transport buffers containing 100 nM of the radiolabeled substrates and increased concentrations of the substrates with and without ketamine at the concentrations giving the IC⁵⁰values. Uptake was determined after 6 min. The y axes represent percent control values, which were obtained by dividing the uptake values in the presence of ketamine and increased concentrations of each substrate by those in the absence of ketamine. It is noteworthy that the inhibitory effects of ketamine on monoamine transporters were gradually recovered by adding increased concentrations of each nonlabeled substrate. Each point represents the mean +/- SD of two experiments performed in quadruplicate.