Figure 5. (A) Influence of prolonged exposure of the cells to nitrous oxide (N²O), by changing the extracellular fluid (4 ml/min) with N sub 2 O-saturated medium during 9 min, is shown. Cells (n = 9), in whole-cell configuration, were exposed to muscimol at time intervals as shown. All data are normalized to chloride (Cl sup -) current as induced with 10 micro Meter muscimol under “air” conditions. Although the short-term exposure to N²O increases the muscimol-induced Cl sup - current with [nearly =] 40%, further increase with 50% can be observed with prolonged exposure to N²O. Replacement of this medium with the one without N²O (4 ml/min) resulted in a slow recovery to original levels. Asterisks indicate significant differences between the measurements and controls, indicated as “air” on the x axis. A significant difference is found between 9 min of long-term exposure and short-term exposure to N²O. Bars represent SEM of these values. (B) A N²O concentration-response relation is shown. Every cell was exposed to only one concentration of N²O dissolved in the extracellular fluid. The muscimol-induced Cl sup - peak current under N sub 2 O exposition was for every cell normalized to the current obtained without the anesthetic in the same cell. Bars represent SEM. The number of measurements for each concentration of N²O is given in parentheses. Because the minimum alveolar concentration for N²O in rodents is higher than the atmospheric pressure, the concentration-response relation could be constructed only partially.