Facilitation de r�actions nociceptives par la naloxone chez la souris et chez le rat

Abstract

The effects of graded doses of naloxone on nociceptive reactions of mice and rats of different strains were studied using a hot plate technique. Enhancements were observed provided the control reaction times were long enough, a condition which was fulfilled for the jumping reaction at different temperatures of the hot plate (50‡ C, 55‡ C, 65‡ C, 80‡ C in mice-55‡ C in rats) but for the licking reaction only at the lowest temperature (50‡ C in mice). Enhancement was dose-related up to a ceiling effect. Nalorphine had no such overt action. As low doses of naloxone (0.1–1 mg/kg s.c.) were effective, the enhancement is most simply accounted for by interactions at the level of the specific opioid receptors, some of which are suggested. The phenomenon might be relevant to the interpretation of the mechanisms of precipitated abstinence.