Fig. 6. Effect of halothane (1.1%) anesthesia on activity of a spinal dorsal horn neuron. (  A ) Examples of responses of a spinal dorsal horn neuron to nonnoxious and noxious stimuli before administration of 1.1% halothane and before and 2 h after the incision under anesthesia with 1.1% halothane. BR, brush stimulation; VF, 4-g von Frey hair stimulation; PP, pinprick stimulation; PI, pinch stimulation. (  B ) Examples of low-threshold and high-threshold receptive fields (RFs) of a spinal dorsal horn neuron before administration of 1.1% halothane and before and 2 h after the incision under anesthesia with 1.1% halothane. The data in A and B were obtained from the same neuron. Administration of 1.1% halothane decreased the low-threshold RF, and expansion of the low-threshold RF is minimum (  arrow ). (  C ) Mean changes in responses of spinal dorsal horn neurons (n = 5) to brushing and pinching stimuli and low-threshold and high-threshold RF sizes before ad-ministration of 1.1% halothane and before and after the incision under anesthesia with 1.1% halothane. *  P < 0.01  versus pre (before administration of 1.1% halothane).†  P < 0.05  versus before incision under anesthesia with 1.1% halothane.