Inhibition of rat spinal cord dorsal horn neurons by non-segmental, noxious cutaneous stimuli

Extracellular single unit recordings were obtained from spinal cord dorsal horn neurons in halothane-anesthetized rats. Inhibitory effects induced by noxious mechanical or electrical stimuli applied to a remote area of the body surface were assessed on the spontaneous or evoked activity of these cells. Noxious mechanical stimulation inhibited 59% of the cells receiving nociceptive inputs (wide dynamic range and nociceptive specific) but only 5% of the other cell types. Inhibition produced by mechanical stimulation lasted for the full duration of stimulus application (up to 30 s) whereas inhibition produced by electrical stimulation lasted less than 500 ms. Increasing the depth of anesthesia was found to depress or abolish the inhibition.