Abstract
In the dental or periodontal treatment, laser is commonly used to relieve pain. We have reported the direct effects of the Nd:YAG laser sweeping irradiation on nerve discharges of Xenopus tactile nerve fibers. Nerve discharges were reversibly suppressed with the sweeping irradiation. But the effect of sweeping irradiation is not clear. In this study, we tried to clarify the effect of sweeping irradiation by comparison with non-sweeping irradiation. Dorsal surface skin of Xenopus was removed together with fine tactile nerve bundles. Chinese ink was painted on a dissected fine nerve bundle. From this bundle, nerve discharges with tactile stimuli on the skin surface were recorded by a silver electrode, and counted by the spike counter. After non contact Nd:YAG laser sweeping irradiation or after non-sweeping irradiation, tactile responses were periodically recorded with paying enough attention to stimulate the same surface area under the dissection microscope. Results were followings. 1) With sweeping irradiation, nerve discharges were reversibly suppressed. 2) With non-sweeping irradiation, nerve discharges were suppressed within a few seconds. And it is very difficult to recover from the suppression. In most cases, the suppression was irreversible. These results show the efficacy of the sweeping irradiation. [Jpn J Physiol 54 Suppl:S251 (2004)]
