Halothane reduces the inhibition of dorsal horn lamina V type neuronal activity induced by bradykinin injection into the femoral artery contralateral to the recording site

Effect of halothane (0.2%, 0.5%, and 1.0%) on spinal function were studied in lamina V type cells responding to noxious and light touch applied at their cutaneous receptive field on the foot pad of the left hind paw. Extracellular unit activities of lamina V type cells were recorded at the lumbar level in six cats and thirteen spinal cats. When intra-arterial injection of bradykinin (BK) 10 micrograms into the femoral artery ipsilateral to the recording sites was used as the noxious test stimuli, six of these cells (100%) were found to have inhibitory response in six intact cats and thirteen of these cells (100%) were found to have excitatory response in thirteen spinal cats. On the other hand, when the injection of 10 micrograms into the femoral artery contralateral to the recording sites was used as the noxious test stimuli, six of these cells (100%) were found to have inhibitory response in six intact cats and six of these cells (46%) were found to have inhibitory response in thirteen spinal cats. We studied the effect of halothane on the inhibition induced by BK injection into the femoral artery contralateral to the recording sites in six intact cats and six spinal cats. Halothane 0.2%, 0.5% and 1.0% reduced the inhibition of dorsal horn lamina V type neuronal activity induced by BK injection.