The effect of xenon on spinal dorsal horn neurons: a comparison with nitrous oxide.

We compared the effects of xenon (Xe) on the spinal cord dorsal horn neurons with those of nitrous oxide (N2O) in cats anesthetized with chrolarose and urethane. We assessed the potency of both anesthetics by the inhibition of wide dynamic range neuron responses evoked by cutaneous noxious (pinch) stimulation to a hindpaw. During 70% Xe inhalation, the responses of 7 of 11 neurons to pinch stimulation were suppressed. N2O, 70%, suppressed it in 8 of 11 neurons. The potency of Xe and N2O was compared in six neurons that were suppressed by both anesthetics. After 20 min of Xe inhalation, the response to pinch was suppressed to 49.5% +/- 8.2% (mean +/- SE), while N2O, 70% in oxygen, suppressed it to 45.9% +/- 7.9%. The difference between N2O and Xe was not significant. We conclude that Xe and N2O suppress the spinal cord dorsal horn neurons to a similar degree.