MODIFICATION OF THE ANTINOCICEPTIVE EFFECT OF MORPHINE BY CENTRALLY ADMINISTERED DIAZEPAM AND MIDAZOLAM

Abstract
1 Intracerebroventricular administration of diazepam or midazolam decreased the antinociceptive effect of morphine in rats as measured by the ‘tail flick’ method. 2 Midazolam, injected into the periaqueductal grey matter (PAG) antagonized the analgesic effect of morphine. The action of midazolam was partially reversed by bicuculline. 3 These findings support the view that the effect of benzodiazepines on morphine antinociception may be mediated through γ-aminobutyric acid receptors.