Articles: hyperalgesia.
-
MPV-2426 is a novel alpha2-adrenoceptor agonist developed for spinal pain therapy. It has proved to be effective in physiologic and neuropathic conditions. In the current study its effectiveness on mechanical hyperalgesia was assessed in a rat model of postoperative pain. ⋯ Intrathecal MPV-2426 dose-dependently attenuates postoperative hyperalgesia to mechanical stimulation because of an action on alpha2 adrenoceptors. Its antihyperalgesic action is as effective as that produced by dexmedetomidine and is considerably stronger than that produced by clonidine. However, preoperative treatment with MPV-2426 does not prevent the development of postoperative hyperalgesia.
-
J. Peripher. Nerv. Syst. · Jun 2000
Epineurial application of TNF elicits an acute mechanical hyperalgesia in the awake rat.
Tumor necrosis factor alpha (TNF) injected into the sciatic nerve and neutralizing antibodies to its receptor injected around the nerve are respectively associated with inducing and blocking pain behavior beginning 1 to 3 days post-injection. This study examined the acute effects of TNF applied around the nerve trunk on the mechanical threshold (determined with von Frey hairs) and withdrawal latency to radiant heat. TNF (0.9 and 7.7 ng in 90 microL) injected onto the nerve via an indwelling catheter elicited a decrease in mechanical threshold. ⋯ Identical doses of TNF injected near, but not on the nerve, 90 ng of TNF injected on the nerve, and vehicle were without effect on either modality. These data indicate that effects of acutely administered TNF to the nerve trunk are capable of producing modality specific pain behavior. These changes may represent a first step in TNF-induced neuropathic pain.
-
Neuroscience letters · May 2000
Involvement of spinal protein kinase C in induction and maintenance of both persistent spontaneous flinching reflex and contralateral heat hyperalgesia induced by subcutaneous bee venom in the conscious rat.
To further study the roles of spinal protein kinase C (PKC) in induction and maintenance of both the persistent spontaneous nociception and the contralateral heat hyperalgesia induced by subcutaneous (s.c.) bee venom injection, the effects of intrathecal (i.t.) treatment with a PKC inhibitor, chelerythrine chloride (CH), were evaluated in conscious rats. Pre-treatment i.t. with CH at three doses of 0.01, 0.1 and 1 nmol produced a dose-dependent suppressive effect on the flinching reflex with the inhibitory rates of 39, 48 and 59%, respectively, when compared with the pre-saline control group. ⋯ Post-treatment i.t. with the drug at the highest dose used (1 nmol) also resulted in a 35% reversal effect on the established contralateral heat hyperalgesia. The present result suggests that activation of PKC in the spinal cord contributes to the induction and maintenance of both peripherally-dependent persistent spontaneous pain and contralateral heat hyperalgesia which is dependent upon central sensitization.
-
Randomized Controlled Trial Clinical Trial
Effect of preoperative oral dextromethorphan on immediate and late postoperative pain and hyperalgesia after total abdominal hysterectomy.
Dextromethorphan is a noncompetitive N-methyl-D-aspartate (NMDA) receptor antagonist known to inhibit wind-up and NMDA-mediated nociceptive responses of dorsal horn neurons. Experimental and clinical studies indicate that NMDA-receptor antagonists may potentiate the effect of analgesics such as morphine, local anesthetics and NSAIDs. Results from previous clinical studies of dextromethorphan in postoperative pain are conflicting, possibly related to administration of insufficient doses of the drug. ⋯ There were no significant differences in side-effects (nausea, vomiting, sedation). In conclusion, oral dextromethorphan 150 mg reduced PCA morphine consumption immediately (0-4 h) after hysterectomy, without prolonged effects on pain or wound hyperalgesia. A positive correlation between the magnitude of wound hyperalgesia at 24 h after operation, and total 24 h postoperative PCA morphine consumption was demonstrated.
-
Randomized Controlled Trial Clinical Trial
Spatial mapping of the zone of secondary hyperalgesia reveals a gradual decline of pain with distance but sharp borders.
The purpose of this study was to examine how pain to punctate mechanical stimuli varies with position within the zone of secondary hyperalgesia. Secondary hyperalgesia was produced by an intradermal injection of capsaicin (50 microg) into the volar forearm of human volunteers (n=9). Before and at 20, 60 and 100 min after the capsaicin injection, a computer-controlled electromechanical stimulator was used to deliver controlled-force stimuli to the skin via a 12-mm wide, 100-microm thick blade probe. ⋯ This finding unlikely reflects a ceiling effect because pain ratings within the zone of secondary hyperalgesia increased linearly with force. The relatively uniform pain ratings to the blade stimuli within the zone of secondary hyperalgesia and the sharp border that delimits the zone of hyperalgesia indicate that this sensory disturbance approaches being an 'all-or-nothing' phenomenon. Thus, a two-state model for central plasticity is needed to explain secondary hyperalgesia.