Fig. 2. Voltage responses from four different neurons during application of air-puff stimuli (left trace) and pinch stimuli (right trace). Bars above the traces show the duration of the stimulation. Substantia gelatinosa (SG) neurons exhibit several response profiles during nonnoxious and noxious mechanical stimuli. ( A ) Multireceptive neurons exhibited depolarizations in response to nonnoxious air-puff stimuli and noxious pinch stimuli. These neurons were more sensitive to pinch stimuli than air-puff stimuli. ( B ) Nociceptive neurons responded maximally (fired action potentials) to pinch stimuli with or without subthreshold depolarizations during air-puff stimuli. ( C ) subthreshold neurons responded to air-puff stimuli and pinch stimuli with small depolarizations that failed to reach action potential threshold. ( D ) Light-touch neurons responded maximally to air-puff stimuli. These neurons also responded to pinch stimuli, but action potentials were restricted to the beginning and end of pinch stimuli.