INFLAMMATION REVEALS INHIBITION OF NOXIOUS RESPONSES OF RAT SPINAL NEURONS BY CARBAMAZEPINE

The effect of subcutaneously administered carbamazepine, a sodium chan nel blocker, on the electrically evoked C-fibre (noxious) vs A beta fi bre (innocuous) responses of dorsal horn neurones in non-inflamed and inflamed rats (3 h after plantar injection of carrageenan) was studied . Carbamazepine (0.5-5 mg/kg) significantly reduced the noxious evoked responses of the neurones under inflammatory, but not non-inflamed, c onditions. The innocuous evoked responses of the neurones were not sen sitive to carbamazepine under any conditions and administration of the vehicle alone did not influence any evoked response of these neurones . We propose that there are changes in the type, or proportion of, sod ium channels underlying the transmission messages following peripheral inflammation which become sensitive to carbamazepine.