Bilateral experimental muscle pain changes electromyographic activity of human jaw-closing muscles during mastication.
The effects of bilateral experimental muscle pain on human masticatory patterns were studied. Jaw movements and electromyographic (EMG) recordings of the jaw-closing muscles were divided into multiple single masticatory cycles and analyzed on a cycle-by-cycle basis. In ten men simultaneous bilateral injections of hypertonic saline (5%) into the masseter muscles caused strong pain (mean+/-SE: 7.5+/-0.4 on a 0-10 scale), significantly reduced EMG activity of jaw-closing muscles in the agonist phase, and significantly increased EMG activity in the antagonist phase. Nine of the subjects reported a sensation of less intense mastication during pain. Injections of isotonic saline (0.9%) did not cause pain or significant changes in masticatory patterns. The influence of higher brain centers on conscious human mastication can not be discarded but the observed phase-dependent modulation could be controlled by local neural circuits and/or a central pattern generator in the brain stem which are capable of integrating bilateral nociceptive afferent activity.
Svensson
P
P
Department of Prosthetic Dentistry, Aarhus University, Denmark. psv@miba.auc.dk
Houe
L
L
Arendt-Nielsen
L
L
D000328:Adult; D004576:Electromyography; D006801:Humans; D008297:Male; D008409:Mastication / Q000502:physiology*; D008410:Masticatory Muscles / Q000503:physiopathology*; D010146:Pain / Q000503:physiopathology*