Figure 2. The effect of halothane applied before stimulation with acetylcholine or aluminum fluoride (AlF^4-). (A) Representative recordings from the strips stimulated first with 0.3 [micro sign]m Ca²⁺and with additional 10 [micro sign]m acetylcholine plus 10 [micro sign]m guanosine triphosphate (GTP) in the absence (control) or presence of halothane. Halothane was applied from 10 min before the stimulation with 0.3 [micro sign]m Ca²⁺. Traces are overlapped so the forces induced by 10 [micro sign]m Ca²⁺conform with each other. (B) Forces induced by 0.3 [micro sign]m Ca²⁺alone, Ca²⁺plus 10 [micro sign]m acetylcholine and 10 [micro sign]m GTP, Ca²⁺plus AlF^4-(1 mm NaF, 10 [micro sign]m AlCl³), and 10 [micro sign]m GTP in the absence (open column; control) or presence (hatched column) of halothane are expressed as percentages of maximal force induced by 10 [micro sign]m Ca²⁺, with SD shown by vertical bars (n = 5). Halothane did not affect the contractions induced by 0.3 [micro sign]m Ca²⁺alone, but it attenuated subsequent increases in force (Ca²⁺sensitization) induced by either acetylcholine (*P < 0.05) or AlF^4-(**P < 0.01). The control contractions induced by acetylcholine or AlF^4-at 0.3 [micro sign]m Ca²⁺did not differ, nor did the inhibition produced by halothane on the force produced by either stimulation method.