title: Morphine sensitivity of spinal neurons in the chronic constriction injury neuropathic rat pain model.
abstract: Opioid analgesia involves suppression of neuronal activity in central sensory pathways. We show that the classic opioid morphine reduces spinal neuronal spontaneous and evoked activity after induction of neuropathy by chronic constriction injury of the sciatic nerve in rats. The minimal effective dose of morphine was 0.3 mg/kg for most response parameters tested. Morphine sensitivity of spinal cord neurons is similar across neuropathic pain models. We therefore conclude that nerve damage per se rather than the experimental model determines the effectiveness of opioids in general and investigate several pain measurement endpoints which might be important to clinically determine morphine's efficacy in neuropathic pain.
authors.affiliation: Boehringer Ingelheim Pharma GmbH & Co KG, CNS Research, 88400 Biberach, Germany. Electronic address: silke.hirsch@arcor.de.
authors.forename: Silke J
authors.initials: SJ
authors.lastname: Hirsch
authors.affiliation: Neuroscience, Physiology and Pharmacology, University College London, Gower Street, London WC1E 6BT, United Kingdom.
authors.forename: Anthony H
authors.initials: AH
authors.lastname: Dickenson
mesh_terms: D000701:Analgesics, Opioid / Q000494:pharmacology*; D000818:Animals; D002908:Chronic Disease; D003250:Constriction; D004195:Disease Models, Animal; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009437:Neuralgia / Q000188:drug therapy* / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D010147:Pain Measurement; D010523:Peripheral Nervous System Diseases / Q000188:drug therapy*; D051381:Rats; D017208:Rats, Wistar; D012584:Sciatic Nerve / Q000187:drug effects* / Q000293:injuries
chemical_list: D000701:Analgesics, Opioid; D009020:Morphine
keywords: Chronic constriction injury; In vivo electrophysiology; Morphine; Neuropathy; Pain; Spinal cord