Fig. 2. Effects of nonhalogenated alkanes cyclopropane and butane on recombinant GABA^Aand glycine receptors. (A ) Cyclopropane (1, 2, and 5 minimum alveolar concentration [MAC]) significantly enhanced the current responses of α¹glycine receptors to an EC⁵of agonists. On α¹(S267C) mutant receptor, the enhancing effect of cyclopropane (5 MAC) was completely eliminated. On the other hand, GABA^Areceptors required 5 MAC of cyclopropane for a small, but significant, potentiation. Cyclopropane showed similar effects on α²β¹GABA^Areceptors. (B ) Butane (1 MAC) significantly enhanced the α¹glycine and the α²β¹GABA^Areceptors with much higher potentiation of the glycine receptors than the GABA^Areceptors. Error bars represent SEM; n = 6–13 oocytes.