학술논문
Continuous intravenous infusion of naloxone does not change behavioral, cardiovascular, or inflammatory responses to subcutaneous formalin in the rat.
Document Type
Academic Journal
Author
Taylor BK; W.M. Keck Foundation Center for Integrative Neuroscience, University of California San Francisco 94143-0452, USA. brad@phy.ucsf.edu; Peterson MA; Basbaum AI
Source
Publisher: Lippincott Williams & Wilkins Country of Publication: United States NLM ID: 7508686 Publication Model: Print Cited Medium: Print ISSN: 0304-3959 (Print) Linking ISSN: 03043959 NLM ISO Abbreviation: Pain Subsets: MEDLINE
Subject
Language
English
ISSN
0304-3959
Abstract
The opioid antagonist, naloxone, produces equivocal effects on the magnitude of nociceptive responses in several animal models of persistent pain, including the formalin test. Hindpaw injection of dilute formalin produces not only inflammation but also phasic (Phase 1) and persistent (Phase 2) behavioral and cardiovascular nociceptive responses in the rat. To test the hypothesis that endogenous opioid systems contribute to the magnitude of responses to intraplantar formalin injection, we evaluated the effects of continuous naloxone administration (0.01-100 mg/kg per h, i.v.) on formalin-evoked hindpaw inflammation, on behavioral indices of pain, flinching and licking pain behavior, and on changes in mean arterial pressure and heart rate. We report that naloxone, at doses less than 100 mg/kg per h, did not change any formalin-evoked response. Although the 100 mg/kg per h dose significantly decreased these responses, it also produced muscle rigidity and profound bradycardia. We conclude that endogenous opioids do not significantly modulate the nociceptive processing induced by subcutaneous formalin.