• Keiko Fujii-Abe, Yuka Oono, Katsunori Motohashi, Haruhisa Fukayama, and Masahiro Umino.
• Department of Dental Anesthesiology, School of Dental Medicine, Tsurumi University, Yokohama, Japan. fujii-keiko@tsurumi-u.ac.jp
• Pain Med. 2010 Jun 1;11(6):825-33.

BackgroundThe diffuse noxious inhibitory control (DNIC) effect is the neurophysiological basis for the phenomenon that heterotopic "pain inhibits pain" in remote areas of the body. The effect of DNIC is mediated by spino-bulbo-spinal loops and a final postsynaptic inhibitory mechanism. The DNIC effect depends on intensity, duration, quality, and application site of conditioning stimulation and stimulated nerve fiber-type. DNIC induced by CO(2) laser conditioning stimulation has, however, not yet been investigated, and the present study was designed to examine this.MethodsAs the indicator of test stimulation, the late component of somatosensory evoked potentials (SEPs) induced by electrical tooth stimulation and pain intensity were examined under CO(2) laser conditioning stimulation. As the conditioning stimuli, CO(2) laser energy (lambda = 10.6 microm, spot size Ø = 2 mm) was applied to the dorsum of the left hand.ResultsThe maximum reductions in SEP amplitude and pain intensity evaluated using a visual analog scale were 34.7% and 28.7%, respectively during CO(2) laser conditioning stimulation. No aftereffect was observed.ConclusionThe present study revealed that CO(2) laser radiation attenuated the late component of SEPs induced by electrical tooth stimulation, triggering the DNIC effect but with no aftereffect.

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