Effect of He-Ne laser irradiation on synaptic transmission of the superior cervical sympathetic ganglion in the rat.

The effect of low-power He-Ne laser on synaptic transmission was studied in the superior cervical sympathetic ganglion of Wistar rats. Extracellular and intracellular recordings were made from isolated ganglia before and after laser irradiation. In addition, effects of ganglion irradiation on skin blood flow were observed in in vivo preparations. Irradiation on the isolated ganglion decreased the amplitude of evoked compound action potentials in the extracellular recordings. Intracellular recordings from ganglion cells revealed that the neuronal membrane was hyperpolarized, while threshold potential and latency of response were unchanged. The reduction of skin blood flow during preganglionic nerve stimulation lessened by irradiation on the ganglion. Our results indicate that low-power He-Ne laser depresses sympathetic ganglionic transmission, and hyperpolarization of ganglionic cells takes part in the mechanism of action.