Figure 2. Effect of ketamine (10 micro Meter to 1 mM) on the ratio of fluorescence intensities due to excitation at 340 and 380 nm (F³⁴⁰/F³⁸⁰, an index of intracellular calcium concentration). At submaximal (0.1 micro Meter acetylcholine; open circles; n = 6) and maximal (10 micro Meter acetylcholine; filled circles; n = 6) doses, ketamine caused a dose-dependent decrease in F³⁴⁰/F³⁸⁰and thus in the intracellular calcium concentration. There was no difference in response between the two different acetylcholine concentrations. Values are means +/- standard deviations.