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• Assess temporal summation to heat stimulation in fibromyalgia patients and controls. It was concluded that fibromyalgia patients had increased pain responses to repeated heat stimuli compared to control subjects suggesting involvement of central sensitisation in fibromyalgia.

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• The exaggerated referred pain areas evoked by hypertonic saline and facilitated temporal summation to intramuscular electrical stimulation previously found in fibromyalgia patients (71) was pharmacologically decreased by ketamine (an NMDA-antagonist) targeting central sensi-tisation. The facilitated mechanisms for referred pain and temporal summation were reduced by ketamine compared to placebo which strongly indicate involvement of central sensitisation in fibromyalgia.

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• Assess referred pain pattern to intramuscular infusion of hypertonic saline and the muscle sensitivity to pressure in areas within and outside the region involved in the whiplash trauma. Hyperalgesia to pressure and enlarged referred pain areas were found in patients with chronic whiplash syndrome compared to control subjects both within and outside the traumatized area suggesting central sensitisation.

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• This study shows that persistent joint chronic nociceptive input can facilitate the central processing of muscle nociceptive input in humans. Muscle sensitivity and referred pain pattern was assessed in knee osteoarthritis patients by intramuscular infusion of hypertonic saline into the tibialis anterior muscle. Increased pain intensity and enlarged pain areas were found in patients versus controls suggesting involvement of central sensitisation.

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•This study describes the influence of ongoing rheumatoid arthritic pain, with two different disease durations, on somatosensory sensitivity and descending inhibitory pain control mechanism. Beside hyperalgesia pressure over the painful joint also widespread hyperalgesia to pressure was found in the patient group with the longest disease duration compared to controls. The descen-ding inhibitory control of pain was not affected in any of the patient groups compared to controls. The widespread hyperalgesia to pressure detected in the group with long-term pain conditions indicated development of central sensitisation.

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