Fig. 3. ( A ) A representative recording of the integrated C4 activity (∫C4) before, during, and after separate superfusion with sevoflurane solution ( upper trace : medulla; lower trace : spinal cord). The horizontal bars indicate the duration of superfusion with sevoflurane. ( B ) The effect of separate perfusion of 0.74 mm (2.11 minimum alveolar concentration [MAC]) sevoflurane on C4 burst rate ( left ) and amplitude ( right ). C4 burst amplitude decreased significantly upon application of sevoflurane to the spinal cord. On the other hand, C4 burst rate decreased significantly when sevoflurane was applied to the medulla. * P < 0.05 versus control. *** P < 0.005 versus control. ††† P < 0.005, medulla perfusion group versus spinal cord perfusion group.