The pharmacology of the inhibition of dorsal horn neurones by impulses in myelinated cutaneous afferents in the cat.

The effects of microelectrophoretic strychnine and bicuculline methochloride were studied on the time course of synaptic inhibitions of single dorsal horn neurones in the lumbar spinal cord of cats anaesthetized with pentobarbitone. The inhibitions, evoked by volleys in mixed myelinated cutaneous afferents, varied in latency and duration. In general, early inhibitions (latency less than 12msec; duration less than 36 msec) were reduced by microelectrophoretic strychnine whereas late inhibitions (latency more than 16 msec and more prolonged in duration) were usually sensitive to bicuculline. These results can be interpreted in terms of glycine and GABA as the inh ibitory transmitters of early and late inhibitions respectively.