Fig. 6. Effects of dissociative anesthetics on 5-hydroxytryptamine³(5-HT³) receptors. (A ) The ketamine dose–inhibition relations for the currents evoked by different concentrations of 5-HT (n = 6–8). (B ) The dizocilpine dose–inhibition relations for the currents evoked by different concentrations of 5-HT (n = 4–6). (C ) Effects of ketamine on the 5-HT concentration–response curve. The concentration–response relations for 5-HT before and during perfusion of 300 μM ketamine were examined. The agonist concentration for half-maximal response (EC⁵⁰) values of the 5-HT³receptors before and during treatment with ketamine were 1.6 ± 0.4 and 2.8 ± 0.2 μM, and Hill coefficient values of those were 2.3 ± 0.3 and 2.1 ± 0.3, respectively (n = 4).