Abstract
Intraperitoneally administered benzodiazepines, chlordiazepoxide (2-5 mg/kg), diazepam (1 mg/kg), flurazepam (1 mg/kg) and a benzodiazepine antagonist, Ro 15-1788 (0.5 mg/kg), reversed the antinociceptive effect in mice which was induced by intracisternal administration of 1 μg of sulfated cholecystokinin octapeptide. The antinociceptive effect of cholecystokinin was reversed by naloxone, suggesting that the antinociceptive action involves endogenous opioid peptides in its production. On the other hand, morphine-induced analgesia was not reversed by diazepam and Ro 15-1788. These facts rule out opioid receptors as the site of the antagonism between the benzodiazepines or Ro 15-1788 and cholecystokinin on the antinociceptive effect. Benzodiazepines and Bo 15-1788 seem to inhibit the release of opioid peptides induced by cholecystokinin.
