15th World Congress of Pain, Buenos Aires, Arjantin, 10 Kasım 2014
Aim of Investigation:
Central nervous system controls the skin temperature simultaneously. The skin surface temperature may provide valuable information for diagnostics in some pathological conditions.(1-2) Exteroceptive Supression Period of muscles EMG activity is an indicator for muscular disorders. Electrophysiological parameters of muscles are influenced by temperature (3). There is lack of information in literature about the exteroceptive reflex parameters during temperature changes of masseter muscle. In this study, we tested if the exteroceptive reflex could be modulated by experimental temperature application on the masseter muscle of healthy human.
Methods: Twelve healthy young men (mean ± SEM age: 25.6 ± 0.9 years) and 12 age-matched healthy women participated in the experiment. Thermal application of 10 °C (cooling), 32°C (baseline) and 42 °C (warming) were applied to the skin over the right masseter muscle using a thermode (30 x 30 mm, PATHWAY, Medoc, Israel). The jaw-exteroceptive reflexes were recorded with surface EMG electrodes during cooling, baseline and warming on the masseter muscle. Pre-stimulus EMG, Onset, Offset and Peak-peak of reflex amplitude of the reflex were analysed with Wilcoxon signed-rank test.
Results: Onset values for ES1 reflex are 13,31 ms for cooling, 13,2 ms for warming and 12,41 ms for baseline. Onset values for ES2 reflex are 48,02 ms for cooling, 44,09 ms for warming, 45,09 ms for baseline. There were no difference for onset and offset values of different temperatures. Duration of ES1 reflex were 19,4 ms for cooling, 18,24 ms for warming and 20,94 ms for baseline. Duration of ES2 reflex were 36,55 ms for cooling , 37,56 ms for warming and 42,76 ms for baseline. The peak-peak values / background EMG of ES1 reflex during cooling is significantly different compared to baseline (p=0.006) and warming (p=0.003). However, for the ES2 reflex there were no difference for cooling, warming and baseline. Conclusions: The suppression effect of exteroceptive reflexes may be a response of inhibitory controls which triggered by different temperatures from other sensory signals. The muscle electrophysiological parameters could be changed in different temperature conditions.