Physiologic and pharmacologic properties of the nucleus caudalis of the trigeminal complex were studied using an extracellular microelectrode recording technique in unanesthetized, mechanically ventilated, decerebrate cats after removal of the neural arch of the first cervical spine. Central trigeminal nociceptors were identified in the magnocellularis portion of the dorsal horn of the first cervical segment of the spinal cord. This finding resolved an apparent “paradox” reported previously. Cells responding to low-threshold cutaneous stimuli applied to the ipsilateral face were found dorsal and rostral to the central trigeminal nociceptors. Nitrous oxide (75 per cent) suppressed the spontaneous firing frequency of the central trigeminal nociceptors by 31-35 per cent, but facilitated spontaneous activity of the low-threshold cutaneous receptors of the nucleus caudalis by 20-31 per cent. The differential effects of nitrous oxide on trigeminal neurons were analogous to the effects of nitrous oxide on the nuclear aggregates of the dorsal horn of the feline lumbar spinal cord.