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Investigation of Offset Analgesia during Acute Central Sensitization, Opioid Administration and Complex Regional Pain Syndrome

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title
Investigation of Offset Analgesia during Acute Central Sensitization, Opioid Administration and Complex Regional Pain Syndrome
author
Martucci, Katherine Theresa
abstract
Pain is a complex sensory and emotional experience. The information gathered from a noxious stimulus is multi-dimensional including aspects of intensity, quality, unpleasantness, as well as spatial and temporal distribution. The temporal processing of nociceptive information, or the mechanisms supporting how pain is perceived across the timeframe of a stimulus, is one aspect of pain that is disrupted frequently in chronic pain states. For example, patients exhibit symptoms of pain that long outlast the actual duration of the initiating stimulus. However, despite the prevalence of altered temporal processing of pain in chronic pain states, the mechanisms supporting temporal processing of nociceptive information remain largely unknown. Offset analgesia is a pain phenomenon characterized by large decreases in pain intensity evoked by small incremental decreases in noxious stimulus intensity, and it is thought to represent contrast enhancement mechanisms that sharpen awareness of decreases in noxious stimuli. Since offset analgesia may represent temporal contrast enhancement that normally occurs in healthy states, the investigation of mechanisms supporting offset analgesia may clarify how pain is temporally altered in chronic pain. Therefore, offset analgesia was assessed in the following experiments. First, offset analgesia was assessed in healthy volunteers during acute sensitization by topical capsaicin, however, no alterations in offset analgesia by capsaicin-heat sensitization were observed. Second, since opioid mechanisms may play a role in offset analgesia, real-time intensity ratings were assessed in healthy volunteers during administration of an opioid, during opioid antagonism and during opioid-induced hypersensitivity. However, offset analgesia was not significantly altered under any opioid manipulation indicating that offset analgesia occurs primarily by opioid-independent mechanisms. Finally, offset analgesia was assessed in patients with complex regional pain syndrome (CRPS). A proportion of these patients had dramatically altered real- time pain intensity ratings and no offset analgesia. In summary, offset analgesia is not altered by capsaicin-heat sensitization, occurs by mechanisms that are largely opioid-independent, and may be disrupted in a subset of chronic pain patients.
subject
CRPS
nociceptive information
offset analgesia
opioid
pain
temporal processing
contributor
Coghill, Robert C (committee chair)
Kraft, Robert A (committee member)
McHaffie, John G (committee member)
Laurienti, Paul J (committee member)
date
2012-01-18T09:35:26Z (accessioned)
2014-01-18T09:30:08Z (available)
2011 (issued)
degree
Neurobiology & Anatomy (discipline)
embargo
2014-01-18 (terms)
identifier
http://hdl.handle.net/10339/36422 (uri)
language
en (iso)
publisher
Wake Forest University
type
Dissertation

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