Naloxone-induced hypoalgesia: lack of involvement of the GABA-benzodiazepine receptor complex.

Article date: 1992/10/1

PubMed ID: 1332077

Journal name: Pharmacology, biochemistry, and behavior (ISSN: 0091-3057)


Previous evidence has demonstrated that repeated daily administration of the opiate receptor antagonist naloxone prior to assessment of pain sensitivity provokes the development of a nonopioid form of hypoalgesia. The present experiments assessed whether the GABA-benzodiazepine receptor complex may be involved in the mediation of this effect. Male Wistar rats were administered 10 mg/kg naloxone prior to hot-plate tests (48.5 degrees C) for pain sensitivity for 8 consecutive days. Control animals were administered saline prior to, and naloxone 2-4 h after, assessment of pain reactivity. Beginning on the fourth or fifth day of this regimen, animals tested under the influence of naloxone displayed longer paw-lick latencies than controls. Preadministration of the GABAA agonist muscimol (1.0-5.0 mg/kg) and GABAA antagonist bicuculline (0.25-1.0 mg/kg) failed to affect paw-lick latencies in naloxone-tested and control rats. The GABAB receptor agonist baclofen (1.0-5.0 mg/kg) and the benzodiazepine receptor agonist diazepam (1.0-5.0 mg/kg) both elevated paw-lick latencies to the same degree in both groups of animals. These results suggest that the GABA-benzodiazepine receptor complex is not involved in the mediation of naloxone-induced hypoalgesia.

This document is available from: http://directlinks.cc/files/muscimol/1332077.pdf

Author List: Rochford J, Stewart J

Publication Types: Journal Article; Research Support, Non-U.S. Gov't

Substances mentioned in the article: Receptors, GABA-A; Muscimol; Naloxone; Baclofen; Diazepam; Bicuculline;

Mesh terms: Analgesia; Animals; Baclofen/pharmacology; Bicuculline/pharmacology; Diazepam/pharmacology; Male; Muscimol/pharmacology; Naloxone/pharmacology; Pain Measurement/drug effects; Rats; Rats, Wistar; Receptors, GABA-A/drug effects;

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