Effect of sevoflurane on spinal dorsal horn WDR neuronal activity in cats

The effects of sevoflurane (0.5%, 1.5%, and 2.5%) on the spinal dorsal horn wide dynamic range (WDR) neuronal activity were studied in either spinal cord intact or spinal cord-transected cats. Extracellular activity was recorded in the dorsal horn from single WDR neurons responding to noxious and non-noxious stimuli applied to the cutaneous receptive fields on the left hind foot pads of intact cats or decerebrate and spinal cord-transected (L 1-2) cats. The experiment was divided into two sections. When bradykinin (BK) 10 micrograms was injected into the femoral artery contralateral to the recording site as a noxious test stimulus in the spinal cord-transected cat, 7 of 15 WDR neurons gave inhibitory responses which were depressed by 0.5%, 1.5%, and 2.5% sevoflurane. On the other hand, when the injection of BK 10 micrograms into the femoral artery contralateral to the recording site was used in the spinal cord-intact cat, all of 7 WDR neurons gave inhibitory responses, which were significantly depressed by 0.5%, 1.5%, and 2.5% sevoflurane. The results suggest that sevoflurane reduces the inhibition of dorsal horn WDR neuronal activities induced by BK injection in spinal cord-intact cats as well as in spinal cord-transected cats.