Xenon suppresses nociceptive reflex in newborn rat spinal cord in vitro; comparison with nitrous oxide.

Although analgesic action of xenon has been reported, little is known about the effect of xenon at the spinal cord, which plays a crucial role in nociceptive transmission. We studied the effect of xenon on nociceptive reflex (the slow ventral root potential) and the monosynaptic reflex in neonatal rat spinal cord in vitro in comparison with nitrous oxide. Xenon (30%) and nitrous oxide (30%) were applied for 17 min through superfusing artificial cerebrospinal fluid. Xenon and nitrous oxide significantly reduced the amplitude of nociceptive reflex by approximately 70% and approximately 25%, respectively. Xenon and nitrous oxide also significantly reduced the amplitude of the monosynaptic reflex by approximately 35% and approximately 15%, respectively. These results indicate that xenon suppressed the synaptic transmission at the spinal cord, especially those of the slow ventral root potential, which reflect nociceptive transmission.