Effect of experimental posterior temporalis muscle pain on human brainstem reflexes.
OBJECTIVE
To study the modulation of jaw-stretch and blink reflexes by experimental posterior temporalis muscle pain.


METHODS
Thirty healthy volunteers (15 males, 25.5+/-0.6 years and 15 females, 27.4 +/- 1.2 years) were included. Short-latency stretch reflex responses were evoked in the masseter and temporalis muscles by fast stretches (1 mm displacement, 10 ms ramp time) and the blink reflexes were evoked by painful electrical pulses (0.5 ms duration), delivered by a concentric electrode placed on the left lower forehead close to the supraorbital foramen before, during and 15 min after a period with experimentally induced muscle pain.


RESULTS
The normalized peak-to-peak amplitude of the stretch reflex in the painful temporalis was significantly higher during pain in both males and females compared with pre- and post-pain conditions (P < 0.004). The R2 root mean square (RMS) of the blink reflex decreased significantly during muscle pain as compared to the pre-pain (P < 0.03) in both males and females.


CONCLUSIONS
The present results indicated that experimental posterior temporalis muscle pain facilitates the jaw-stretch reflex, whereas the nociceptive specific blink reflex is inhibited.


CONCLUSIONS
Present study suggested that these reflexes are suitable models for probing pontine and medullary pain processing.
Peddireddy
Anitha
A
Orofacial Pain Laboratory, Center for Sensory-Motor Interaction, Aalborg University, Fredrik Bajars Vej 7D-3, 9220 Aalborg, Denmark.
Wang
Kelun
K
Svensson
Peter
P
Arendt-Nielsen
Lars
L
D000328:Adult; D000344:Afferent Pathways / Q000502:physiology*; D001767:Blinking / Q000502:physiology; D001933:Brain Stem / Q000502:physiology*; D004558:Electric Stimulation; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D008406:Masseter Muscle / Q000294:innervation / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology; D009433:Neural Inhibition / Q000502:physiology; D009619:Nociceptors / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D017288:Pain Threshold / Q000502:physiology; D012018:Reflex / Q000502:physiology*; D012026:Reflex, Stretch / Q000502:physiology; D012727:Sex Characteristics; D013703:Temporal Muscle / Q000294:innervation / Q000503:physiopathology*; D014276:Trigeminal Nerve / Q000502:physiology; D014278:Trigeminal Nuclei / Q000502:physiology