The Journal of physiology
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The Journal of physiology · Apr 2005
Comparative StudyThe effect of sleep onset on upper airway muscle activity in patients with sleep apnoea versus controls.
Pharyngeal dilator muscles are important in the pathophysiology of obstructive sleep apnoea syndrome (OSA). We have previously shown that during wakefulness, the activity of both the genioglossus (GGEMG) and tensor palatini (TPEMG) is greater in patients with OSA compared with controls. Further, EMG activity decreases at sleep onset, and the decrement is greater in apnoea patients than in healthy controls. ⋯ Differences in TPEMG among the groups were not significant. These data suggest that the middle-aged men had upper airway function midway between that of young normal men and the abnormal airway of those with OSA. Furthermore it suggests that the initial sleep onset reduction in upper airway muscle activity is due to loss of a 'wakefulness' stimulus, rather than to loss of responsiveness to negative pressure, and that this wakefulness stimulus may be greater in the OSA patient than in healthy controls.
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The Journal of physiology · Apr 2005
Comparative StudyMuscular mechanical hyperalgesia revealed by behavioural pain test and c-Fos expression in the spinal dorsal horn after eccentric contraction in rats.
Delayed onset muscle soreness (DOMS) is quite common, but the mechanism for this phenomenon is still not understood; even the existence of muscle tenderness (mechanical hyperalgesia) has not been demonstrated in experimental models. We developed an animal model of DOMS by inducing eccentric contraction (lengthening contraction, ECC) to the extensor digitorum longus muscle (EDL), and investigated the existence of mechanical hyperalgesia in the EDL by means of behavioural pain tests (Randall-Selitto test and von Frey hair test, applied to/through the skin on the EDL muscle) and c-Fos expression in the spinal dorsal horn. We found that the mechanical withdrawal threshold measured with the Randall-Selitto apparatus decreased significantly between 1 and 3 days after ECC, while that measured by von Frey hairs did not. ⋯ This increase was observed in the superficial dorsal horn of the L4 segment of the ipsilateral side, and was clearly suppressed by morphine treatment (10 mg kg(-1), i.p.). These results demonstrated the existence of mechanical hyperalgesia in the muscle subjected to ECC. This model could be used for future study of the neural mechanism of muscle soreness.