Excitatory actions of experimental muscle pain on early and late components of human jaw stretch reflexes.

摘要: Abstract It has recently been shown that a slow stretch evokes short-latency (probably monosynaptic) and long-latency (polysynaptic) reflex response in human jaw-closing muscles. The effect of nociceptive muscle input on the fusimotor system not investigated detail. In order to investigate sustained pain jaw reflex, two main experiments were performed. Stretch responses evoked masseter temporalis muscles by stretches (1-mm displacement, 40-ms ramp time) before, during 15 min after period experimentally induced pain. experiment I, dose 1.0 M hypertonic or 154 mM isotonic (control) saline was infused random into left for up ( n =12). level excitation at 15% maximal voluntary contraction controlled visual feedback surface EMG (sEMG). II, but with from sEMG right control experiment, both intramuscular (imEMG) recorded masseters; imEMG early (onset: 9–10 ms) late (duration 25 40 components analysed all experiments. Infusion caused moderate (mean score Visual Analogue Pain Scale: 4.9–5.0 cm). peak-to-peak amplitude component painful normalized pre-stimulus activity significantly higher than pre- post-infusion conditions area larger pre-infusion condition Isotonic had no significant reflexes. These results indicate experimental jaw-muscle humans facilitates as well revealed imEMG. This appears be independent related volume effects injected saline. A change sensitivity is suggested an explanation.