Both ipsilateral and contralateral localized vibratory stimulations modulated pain-related sensory thresholds on the foot in mice and humans

Abstract

Atsushi Doi,1,2,* Juntaro Sakasaki,3,* Chikato Tokunaga,4,* Fumiya Sugita,5,* Syota Kasae,6 Keisuke Nishimura,7 Yushi Sato,8 Takako Kuratsu,9 Sariya Hashiguchi,10 Min-Chul Shin,1,2 Megumu Yoshimura11 1Department of Physical Therapy, Kumamoto Health Science University, Kumamoto, Japan; 2Graduate School of Health Sciences, Kumamoto Health Science University, Kumamoto, Japan; 3Department of Rehabilitation, Tokyo-Wangan Rehabilitation Hospital, Narashino, Japan; 4Department of Rehabilitation, Himeno Hospital, Yame, Japan; 5Department of Rehabilitation, Tamana Central Hospital, Tamana, Japan; 6Department of Rehabilitation, Shimizu Hospital, Kyoto, Japan; 7Department of Rehabilitation, Iizuka Hospital, Iizuka, Japan; 8Department of Rehabilitation, Showa Hospital, Shimonoseki, Japan; 9Department of Rehabilitation, Konan Hospital, Kumamoto, Japan; 10Department of Rehabilitation, Asahino-Sogo Hospital, Kumamoto, Japan; 11Nakamura Hospital, Nogata, Japan *These authors contributed equally to this work Purpose: This study was aimed to investigate the effect of localized vibration on sensory thresholds in mice and humans using a novel quantitative method. Participants and methods: The sensory thresholds of 7-week-old male C57BL/6J mice were measured with four sine-wave electrostimulation frequencies (5, 50, 250, and 2,000 Hz) before and after applying 2-minute vibration to the plantar side of the foot in mice. In human participants (16 males and 16 females; mean age, 21.0±0.8 years), the sensory threshold was measured at 50 Hz before and after applying 2-minute and 5-minute vibrations to the dorsal side of the foot. Results: Application of a 2-minute vibration at either the ipsilateral or contralateral side modulated the sensory thresholds elicited by a 5- or 50-Hz right electrostimulation in mice. In human participants, application of a 5-minute vibration at either the ipsilateral or contralateral side modulated the sensory threshold elicited by 50-Hz right electrostimulation, but had no effect on local skin temperature. These results suggest that the right side of pain-related Aδ fibers (50 Hz) or C fibers (5 Hz) was modulated by the localized ipsilateral or contralateral side of vibratory stimuli, respectively, in mice and humans. Conclusion: The ability of contralateral vibration to modify the right sensory thresholds suggests possible involvement of the central nervous system in vibratory modulation. Keywords: vibration, sensory threshold, electrostimulation, central modulation

Keywords

• vibration
• sensory threshold
• electrostimulation
• central modulation