Fig. 3. Summary of the effects of the thiopental enantiomers (25 μm) on (A ) α4β2 neuronal receptors, (B ) α7 neuronal receptors, and (C ) αβγδ muscle receptors. Each pair of histograms shows the mean ± SEM of currents activated by a low or high concentration of acetylcholine in the presence of (left ) S  (−)- and (right ) R  (+)-thiopental either preapplied or coapplied; the currents are expressed as percentages of the controls in the absence of thiopental. The number of oocytes is given by n, and significant differences between the enantiomers are denoted by *(P < 0.05) or **(P < 0.01).