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

Abstract

Intracerebroventricular administration of diazepam or midazolam decreased the antinociceptive effect of morphine in rats as measured by the ‘tail flick’ method. Midazolam, injected into the periaqueductal grey matter (PAG) antagonized the analgesic effect of morphine. The action of midazolam was partially reversed by bicuculline. These findings support the view that the effect of benzodiazepines on morphine antinociception may be mediated through γ‐aminobutyric acid receptors. 1982 British Pharmacological Society