Nonsegmental inhibition of rat dorsal horn neurons by innocuous stimulation.

In rats anesthetized with thiamylal sodium, responses of spinal cord dorsal horn neurons to noxious skin heating of the tail were recorded by extracellular microelectrodes. Inhibition of these responses by innocuous mechanical stimulation (light brushing) of the ipsilateral forelimb was assessed. Short-lasting application (3 min, or less) of light brushing did not inhibit neuronal responses to noxious heating. Long-lasting application (5 min, or more) inhibited responses of these neurons to noxious stimulation. The results indicate that, in the anesthetized rat, remotely applied innocuous cutaneous stimuli can inhibit nociceptive responses of dorsal horn neurons, if applied for a sufficiently long time.