Extracellular recordings were made from dorsal horn neurons in the lumbosacral enlargement in rats anesthetized with halothane (0-8-1.0%). Effects of He-Ne (8.5 mW; 632.8 nm) low power laser irradiation on the dorsal horn neuron responses to subcutaneous injection of formalin(5-10%, 0.1ml) were evaluated. It was observed that the irradiation significantly reduced the formalin induced responses.
The observed inhibition of dorsal horn neuron might explain the clinically alleged analgesia elicited by low power laser irradiation.
