Articles: hyperalgesia.
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Am. J. Physiol. Gastrointest. Liver Physiol. · May 2008
Transient receptor potential vanilloid 4 mediates protease activated receptor 2-induced sensitization of colonic afferent nerves and visceral hyperalgesia.
Protease-activated receptor (PAR(2)) is expressed by nociceptive neurons and activated during inflammation by proteases from mast cells, the intestinal lumen, and the circulation. Agonists of PAR(2) cause hyperexcitability of intestinal sensory neurons and hyperalgesia to distensive stimuli by unknown mechanisms. We evaluated the role of the transient receptor potential vanilloid 4 (TRPV4) in PAR(2)-induced mechanical hyperalgesia of the mouse colon. ⋯ Activation of PAR(2) increases currents in these neurons, evokes discharge of action potentials from colonic afferent fibers, and induces mechanical hyperalgesia. These responses require the presence of functional TRPV4. Therefore, TRPV4 is required for PAR(2)-induced mechanical hyperalgesia and excitation of colonic afferent neurons.
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Reg Anesth Pain Med · May 2008
Comparative StudyThe effect of opioid dose and treatment duration on the perception of a painful standardized clinical stimulus.
The concept of opioid-induced hyperalgesia has recently gained prominence as a contributing factor for opioid tolerance and long-term treatment failure. But whereas the preclinical data for this phenomenon are strong, the mixed clinical data derive primarily from experimental pain models conducted in volunteers and heroin addicts, and nonstandardized clinical stimuli, e.g., surgery. The primary objective of this study is to delineate the effect of opioid dose and treatment duration on pain intensity and unpleasantness ratings following a standardized clinical pain stimulus. ⋯ The results of this study bolster preclinical and experimental pain models demonstrating enhanced pain perception in subjects receiving opioid therapy. This simple clinical model may provide a useful tool in examining opioid-induced hyperalgesia.
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Opioid-induced hyperalgesia (OIH) refers to a phenomenon whereby opioid administration results in a lowering of pain threshold, clinically manifest as apparent opioid tolerance, worsening pain despite accelerating opioid doses, and abnormal pain symptoms such as allodynia. ⋯ Despite initial skepticism and reservations, the phenomenon of OIH in humans is now accepted a clinical reality and a challenge faced by anesthesiologists, intensivists, pain specialists, and other workers in a diverse range of settings from perioperative care to palliative care medicine.
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Whiplash is a heterogenous and in many, a complex condition involving both physical and psychological factors. Primary care practitioners are often the first healthcare contact for individuals with a whiplash injury and as such play an important role in gauging prognosis as well as providing appropriate management for whiplash injured patients. ⋯ The clinical assessment of these factors will be explored as well as direction for appropriate early interventions. An early co-ordinated inter-professional management approach, particularly in patients with a complex clinical presentation involving central hyperexcitability and symptoms of posttraumatic stress will be required.
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The nocebo effect consists in delivering verbal suggestions of negative outcomes so that the subject expects clinical worsening. Here we show that nocebo suggestions, in which expectation of pain increase is induced, are capable of producing both hyperalgesic and allodynic responses. By extending previous findings on the placebo effect, we investigated the role of learning in the nocebo effect by means of a conditioning procedure. ⋯ Therefore, in contrast to placebo analgesia, whereby a conditioning procedure elicits larger effects compared to verbal suggestions alone, learning seems to be less important in nocebo hyperalgesia. Overall, these findings indicate that, by defining hyperalgesia as an increase in pain sensitivity and allodynia as the perception of pain in response to innocuous stimulation, nocebos can indeed produce both hyperalgesic and allodynic effects. These results also suggest that learning is not important in nocebo hyperalgesia compared to placebo analgesia.