Facilitation of A[delta]-fiber-mediated acute pain by repetitive transcranial magnetic stimulation.
BACKGROUND
Repetitive transcranial magnetic stimulation (rTMS) of the motor cortex modulates acute and chronic pain perception. The authors previously showed that rTMS over the primary motor cortex (M1) inhibited capsaicin-induced acute pain ascending through C-fibers.


OBJECTIVE
To investigate the effects of 1-Hz rTMS over M1 on acute experimentally induced pain mediated by Adelta-fibers (i.e., another type of acute pain).


METHODS
The authors examined whether rTMS over M1 affected laser evoked potentials (LEPs) in 13 normal subjects using thulium: yttrium-aluminum-garnet laser stimulation. Subjective pain-rating scores and LEPs obtained under three different conditions--rTMS, realistic sham stimulation, and a control condition with no stimulation--were compared.


RESULTS
The authors found that 1-Hz rTMS over M1 significantly aggravated the subjective pain and enhanced the N2-P2 amplitudes compared with the sham or control sessions. Because the pain-rating scores and the N2-P2 amplitudes correlated positively, the N2-P2 amplitudes in the present study can be regarded as the cortical correlate of subjective pain.


CONCLUSIONS
Together with the authors' previous study on C-fiber pain, this facilitatory effect of repetitive transcranial magnetic stimulation on Adelta-fiber-mediated further strengthens the notion of a relationship between repetitive transcranial magnetic stimulation over M1 and pain perception.
Tamura
Y
Y
Department of Integrative Physiology, National Institute for Physiological Sciences, Okazaki, Japan. ytamura@nips.ac.jp
Hoshiyama
M
M
Inui
K
K
Nakata
H
H
Qiu
Y
Y
Ugawa
Y
Y
Inoue
K
K
Kakigi
R
R
D000208:Acute Disease; D000328:Adult; D005071:Evoked Potentials / Q000502:physiology*; D006801:Humans; D007834:Lasers; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology*; D009412:Nerve Fibers / Q000502:physiology*; D010146:Pain / Q000209:etiology / Q000503:physiopathology*; D010147:Pain Measurement; D050781:Transcranial Magnetic Stimulation