Articles: hyperalgesia.
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Induction of the COX-2 isoenzyme appears to play a major role in the genesis of central sensitization after nociceptive stimulation. This study aimed to investigate the efficacy of a single, oral dose of the specific COX-2 inhibitor-valdecoxib in attenuating the central sensitization - induced secondary hyperalgesia in a heat/capsaicin pain model in healthy volunteers. ⋯ We demonstrated that a single, oral dose of valdecoxib when does not attenuate secondary hyperalgesia induced by heat/capsaicin in a cutaneous sensitization pain model in healthy volunteers.
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Clinical Trial
Opioid tolerance and hyperalgesia in chronic pain patients after one month of oral morphine therapy: a preliminary prospective study.
There is accumulating evidence that opioid therapy might not only be associated with the development of tolerance but also with an increased sensitivity to pain, a condition referred to as opioid-induced hyperalgesia (OIH). However, there are no prospective studies documenting the development of opioid tolerance or OIH in patients with chronic pain. This preliminary study in 6 patients with chronic low back pain prospectively evaluated the development of tolerance and OIH. Patients were assessed before and 1 month after initiating oral morphine therapy. The cold pressor test and experimental heat pain were used to measure pain sensitivity before and during a target-controlled infusion with the short-acting mu opioid agonist remifentanil. In the cold pressor test, all patients became hyperalgesic as well as tolerant after 1 month of oral morphine therapy. In a model of heat pain, patients exhibited no hyperalgesia, although tolerance could not be evaluated. These results provide the first prospective evidence for the development of analgesic tolerance and OIH by using experimental pain in patients with chronic back pain. This study also validated methodology for prospectively studying these phenomena in larger populations of pain patients. ⋯ Experimental evidence suggests that opioid tolerance and opioid-induced hyperalgesia might limit the clinical utility of opioids in controlling chronic pain. This study validates a pharmacologic approach to study these phenomena prospectively in chronic pain patients and suggests that both conditions do occur within 1 month of initiating opioid therapy.
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Glutamate is a primary excitatory neurotransmitter in the mammalian CNS. Glutamate released from presynaptic neurons is cleared from the synaptic cleft passively by diffusion and actively by glutamate transporters. In this study, the role of glutamate transporters in sensory processing in the spinal cord has been investigated in behavioral, in vivo and in vitro experiments. ⋯ Whole cell recordings made from superficial dorsal horn neurons in an isolated whole spinal cord from newborn rats (2-3 weeks old) revealed that bath-applied L-trans-pyrrolidine-2,4-dicarboxylic acid (100 microM) produced partial membrane depolarization, increased spontaneous action potentials with decreased neuronal membrane resistance and time constant, but without significant changes of capacitance. Finally, the amplitude and duration of primary afferent evoked-excitatory postsynaptic currents recorded from neurons in the substantia gelatinosa in the spinal slices from young adult rats (6-8 weeks old) were increased in the presence of L-trans-pyrrolidine-2,4-dicarboxylic acid (100 microM). This study indicates that glutamate transporters regulate baseline excitability and responses of dorsal horn neurons to peripheral stimulation, and suggests that dysfunction of glutamate transporters may contribute to certain types of pathological pain.
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Acta Anaesthesiol Belg · Jan 2006
Randomized Controlled Trial Comparative StudyThe use of intraoperative epidural or spinal analgesia modulates postoperative hyperalgesia and reduces residual pain after major abdominal surgery.
The use of intraoperative multimodal analgesia has clearly improved postoperative pain control, mortality and morbidity after major surgical procedures. However, very few clinical trials have studied the longterm impact of intraoperative epidural or spinal analgesia on chronic postsurgical pain (CPSP) development. Even less studies have evaluated the modulatory effect of intraoperative neuraxial analgesia on objective changes (i.e. mechanical hyperalgesia) reflecting central sensitization. ⋯ An effective intraoperative neuraxial block of nociceptive inputs from the wound using multimodal analgesia--specifically when involving spinal analgesics and antihyperalgesic drugs--contributes to prevent central sensitization and hence reduces CPSP after major abdominal procedures.
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J Manipulative Physiol Ther · Jan 2006
Spinal manipulation reduces pain and hyperalgesia after lumbar intervertebral foramen inflammation in the rat.
To document potential mediating effects of the Activator-assisted spinal manipulative therapy (ASMT) on pain and hyperalgesia after acute intervertebral foramen (IVF) inflammation. ⋯ These studies show that ASMT can significantly reduce the severity and shorten the duration of pain and hyperalgesia caused by lumbar IVF inflammation. This effect may result from ASMT-induced faster elimination of the inflammation and recovery of excitability of the inflamed DRG neurons by improving blood and nutrition supplement to the DRG within the affected IVF. Manipulation of a specific spinal segment may play an important role in optimizing recovery from lesions involving IVF inflammation.