Fig. 1. Histograms depicting retrograde coronary collateral blood flow (expressed as a percentage of baseline) during administration of sevoflurane ([0.5 and 1.0 minimum alveolar concentration [MAC]), after discontinuation of sevoflurane (recovery), and during administration of bradykinin in dogs receiving intracoronary drug vehicle (0.9% saline;top ), iberiotoxin (13 μg/min;middle ), or Nω -nitro-l-arginine methyl ester (l-NAME, 300 μg/min;bottom ). *Significantly (P < 0.05) different from baseline; †significantly (P < 0.05) different from 0.5 MAC sevoflurane; §significantly (P < 0.05) different from recovery.