Botulinum toxin type A does not affect spontaneous discharge but blocks sympathetic-sensory coupling in chronically compressed rat dorsal root ganglion neurons

Objective To study the effect of botulinum toxin type A(BTXA) on spontaneous discharge and sympathetic-sensory coupling in chronically compressed dorsal root ganglion(DRG) neurons in rats.Methods In chronically compressed rat DRG,spontaneous activities of the single fibers from DRG neurons were recorded and their changes observed after BTAX application on the damaged DGR.Sympathetic modulation of the spontaneous discharge from the compressed DRG neurons was observed by electric stimulation of the lumbar sympathetic trunk,and the changes in this effect were evaluated after intravenous BTXA injection in the rats.Results Active spontaneous discharges were recorded in the injured DRG neurons,and 47 injured DRG neurons responded to Ca2+-free artificial cerebrospinal fluid but not to BTXA treatment.Sixty-four percent of the neurons in the injured DRG responded to sympathetic stimulation,and this response was blocked by intravenously injection of BTXA.Conclusion BTXA does not affect spontaneous activities of injured DRG neurons,but blocks sympathetic-sensory coupling in these neurons.