Articles: hyperalgesia.
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The sensitivity of tendon and tendon-bone junction is not fully described although these tissues have high clinical impacts. This study assessed (1) pain intensity and referred pain caused by hypertonic saline injection to the proximal tendon-bone junction (PTBJ), tendon and muscle belly sites of tibialis anterior muscle and (2) pressure pain sensitivity, pre, during and post hypertonic saline injections. Eighteen subjects (14 males and 4 females) participated. ⋯ Hypertonic saline pain at the tendon and PTBJ caused significantly higher (P < 0.001) final VAS scores compared to the muscle belly site. The results indicate the PTBJ and tendon sites are more sensitive and susceptible to sensitisation by hypertonic saline than muscle belly. Furthermore, there may be site specific central changes reflected by the differences in the results regarding sensitivity and summation over time.
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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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Changes in the signaling of wide dynamic range neurons and the expression of glutamate transporters in the lumbar spinal dorsal horn of rats with Taxol-induced hyperalgesia are detailed in this report. Deep spinal lamina neurons have significantly increased spontaneous activity and after-discharges to noxious mechanical stimuli, increased responses to both skin heating and cooling, and increased after-discharges and abnormal windup to transcutaneous electrical stimuli. ⋯ These results suggest a state of increased excitability develops in spinal pain-signaling neurons as a consequence of decreased glutamate clearance. These changes in dorsal horn neurobiology likely in turn contribute to the hyper-responsiveness to sensory stimuli seen in animals treated with Taxol and may play a role in the pain seen in cancer patients receiving Taxol.
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Cold allodynia is a common complaint in patients with peripheral neuropathies. However, cold sensitivity of the different types of sensory afferents present in injured nerves is poorly known. We recorded activity evoked by cold in intact sensory fibers of the skin-saphenous nerve preparation and in axotomized sensory fibers of approximately 21 days-old neuromas of the saphenous nerve of mice, in vitro. ⋯ In conclusion, the transducing capacity to cold stimuli is substantially recovered in neuromas. Furthermore, axotomized fibers maintain the 4-AP-sensitive, voltage-activated, transient potassium conductance that counteracts the depolarizing effects of cold in the majority of intact, cold-insensitive primary afferents. Our results indicate that injured nociceptors do not develop abnormal cold sensitivity, suggesting that other mechanisms underlie the cold-induced allodynia following peripheral nerve injury.
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Comparative Study
Systemic and site-specific effects of A-425619, a selective TRPV1 receptor antagonist, on wide dynamic range neurons in CFA-treated and uninjured rats.
Systemic administration of A-425619, a potent and selective TRPV1 receptor antagonist that does not readily enter the CNS, produces antinociception in several rat models of pathological nociception, including complete Freund's adjuvant (CFA)-induced thermal hyperalgesia. To further understand the peripheral mechanisms of TRPV1-related antinociception, we examined the effects of systemic and site-specific injections of A-425619 on evoked and spontaneous firing of spinal wide dynamic range (WDR) neurons in uninjured rats and rats with peripheral inflammation (CFA; 48 h). In uninjured rats, capsaicin-evoked (1 microg) WDR activity was completely blocked by intraplantar administration of A-425619 (3-100 nmol). ⋯ Spontaneous WDR discharges were unaltered by systemic or site-specific injections of A-425619. Thus noxious thermal stimulation triggers the transmission of TRPV1-related signals to spinal WDR neurons in both inflamed and uninjured animals. The apparent increase in TRPV1 signaling to WDR neurons after injury may be the result of changes to the distribution/sensitization of peripheral TRPV1 receptors.