Fig. 1. Typical example of ketamine effect on neuronal activity in a spinal cord unit excited by urinary bladder distension. (Left ) Neuronal oscillographic tracings before and after treatment. (Right ) Effect of ketamine (10 mg/kg) on neuronal activity evoked by urinary bladder distension. (Inset ) Effect of distant nonsegmental noxious stimulus on spontaneous activity of the unit (type I neuron). Cartoons show convergent cutaneous excitatory receptive fields for noxious and nonnoxious stimuli of the same unit, before and after treatment with ketamine. Dark area indicates excitation by noxious pinch. Hatched area indicates inhibition by noxious pinch.