Fig. 4. Effects of isoflurane on the acetylcholine concentration–response relations of human neuronal nicotinic acetylcholine receptors (hnAChRs). ( A ) The acetylcholine concentration–response of the α2β4hnAChR for acetylcholine before and during perfusion of 200 μM isoflurane in Ba2+–Ringer's solution. The EC50values (μM) of the α2β4hnAChR for acetylcholine before and during perfusion of isoflurane were 77 ± 6 and 131 ± 9, and the Hill coefficient values of those were 1.8 ± 0.1 and 1.6 ± 0.1, respectively ( n = 6 or 7). ( B ) The extent of inhibition of the α2β4hnAChR by 200 μM isoflurane as a function of acetylcholine concentration.