Spinal effect of the cholecystokinin-B receptor antagonist CI-988 on hyperalgesia, allodynia, and morphine-induced analgesia in diabetic and mononeuropathic rats. (Laboratoire de Physiologie, Clermont-Ferrand Cedex 1, France) Pain 2000;88:15-22.

Abstract

This study examined the effect of intrathecal CI-99, an antagonist of the CCK-B receptors, on mechanical hyperalgesia and allodynia in normal, mononeuropathic and diabetic rats. The effect of the combination of CI-988 and IV morphine on mechanical hyperalgesia in diabetic and mononeuropathic rats was evaluated using isobolographic analysis. Although ineffective in normal rats, CI-988 induced antinociceptive effects in diabetic and mononeuropathic rats, suggesting an involvement of the CCKergic system in neurogenic pain conditions. The combination of CI-988 and morphine showed a superadditive interaction in the diabetic rats only. In addition, CI-988 exhibited a weak antiallodynic effect in mononeuropathic rats, and no antiallodynic effect in diabetic rats. These results show the CCK-B receptor blockade-mediated antinociceptive effects and reveal the antinociceptive action of morphine in diabetic rats after CCKergic system inhibition.