Articles: hyperalgesia.
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Reg Anesth Pain Med · Mar 2000
Comparative StudyLack of secondary hyperalgesia and central sensitization in an acute sheep model.
We aimed to determine the following in an experimental acute pain model in sheep: (1) whether multimodal analgesia with intravenous fentanyl and ketorolac was more effective than fentanyl alone; (2) whether secondary hyperalgesia (central sensitization) occurred in adjacent (foreleg) dermatomes after thoracic surgery; (3) whether ketorolac used preemptively influenced the development of secondary hyperalgesia after surgery. ⋯ The results obtained in this acute pain model found no significant evidence of a fentanyl-ketorolac interaction, of central sensitization as shown by secondary hyperalgesia, or of a preemptive analgesic effect.
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Much of our current understanding about chronic pain and the mechanisms of nociception has been derived from animal models (Bennett GJ. Animal models of neuropathic pain. In: Gebhart, GF, Hammond DL, Jensen TS, editors. ⋯ One such model that is frequently used in animals to study pain associated with inflammation is the subcutaneous injection of complete Freund's adjuvant (CFA). For ethical reasons, however, little information is available from humans concerning pain associated with this form of inflammation. Due to an inadvertent subcutaneous injection of CFA into the terminal phalanx of this investigator, a study with an N of 1, was conducted to compare the subjective effects of CFA-induced inflammation with objective measurements.
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Neurological research · Mar 2000
Long-term intrathecal administration of glycine prevents mechanical hyperalgesia in a rat model of neuropathic pain.
Neuropathic pain has been postulated to be mediated, in part, by amino acid neurotransmitters including glycine. The current study examined the effects of continuous intrathecal glycine administration (0.1 mumol 0.5 microliter-1 h-1) on the development of mechanical hyperalgesia and other features of neuropathic pain evoked by unilateral loose ligation of the sciatic nerve in the rat. Each hind paw was tested for withdrawal threshold to mechanical stimuli prior to, and after ligation at intervals of 3, 6, 9, 12 and 16 days. ⋯ Glycine increased the normal mechano-nociceptive responses and prevented the development of mechano-nociceptive hyperalgesia. Spontaneous nociceptive behavior and hind paw dystrophic features, seen in the saline treated rats, were significantly diminished. Our results suggest that spinal cord inhibitory glycinergic activity is important for normal mechano-receptive responsitivity and development of mechano-nociceptive hyperalgesia in this model.
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Randomized Controlled Trial Clinical Trial
Differential effects of systemically administered ketamine and lidocaine on dynamic and static hyperalgesia induced by intradermal capsaicin in humans.
We have examined the effect of systemic administration of ketamine and lidocaine on brush-evoked (dynamic) pain and punctate-evoked (static) hyperalgesia induced by capsaicin. In a randomized, double-blind, placebo-controlled, crossover study, we studied 12 volunteers in three experiments. Capsaicin 100 micrograms was injected intradermally on the volar forearm followed by an i.v. infusion of ketamine (bolus 0.1 mg kg-1 over 10 min followed by infusion of 7 micrograms kg-1 min-1), lidocaine 5 mg kg-1 or saline for 50 min. ⋯ Lidocaine reduced the area of punctate-evoked hyperalgesia significantly. It tended to reduce VAS scores of spontaneous pain but had no effect on evoked pain. The differential effects of ketamine and lidocaine on static and dynamic hyperalgesia suggest that the two types of hyperalgesia are mediated by separate mechanisms and have a distinct pharmacology.
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Randomized Controlled Trial Clinical Trial
Effect of propranolol and granisetron on experimentally induced pain and allodynia/hyperalgesia by intramuscular injection of serotonin into the human masseter muscle.
We have previously reported that intramuscular injection of serotonin (5-HT) into the masseter muscle elicits pain and allodynia/hyperalgesia in healthy subjects. The aim of this study was to investigate whether the 5-HT(3) receptor antagonist granisetron or 5-HT(1A) receptor antagonist propranolol can reduce 5-HT induced pain and allodynia/hyperalgesia in the masseter muscle. Twenty-four healthy individuals (12 males and 12 females) without pain from the masseter muscle region participated. ⋯ The difference between 5-HT and granisetron+5-HT was significant. In conclusion, the results of this study indicate that injection of granisetron and propranolol into the human masseter muscle reduces pain induced by local administration of 5-HT, but that the effect of granisetron is stronger than that of propranolol. In addition, granisetron totally abolishes allodynia/hyperalgesia.