Antinociceptive effect of intracerebroventricular administration of cholecystokinin receptor agonist and antagonist in nerve-ligated mice

In the present study we investigated the effects of intracerebroventricular injection of caerulein, the cholecystokinin receptor agonist and proglumid e, the receptor antagonist on morphine response in the sciatic nerve ligati on in mice. Subcutaneous administration of morphine induced antinociception in the both intact and ligated mice, however, the response of the opioid w as lower in the ligated mice as compared with the intact animals. Caerulein induced antinociception in the non-ligated but not in the nerve-ligated an imals. Combination of caerulein with morphine elicited higher response in l igated animals, however, the response induced in ligated animals was much m ore prominent. Proglumide alone did not elicit any response in both animal groups. The antagonist decreased the response of caerulein in the nonligate d mice. Low doses of proglumide in the combination with caerulein induced a ntinociception in the ligated mice. We conclude that cholecystokinin recept or mechanism(s) may alter morphine resistance induced by nerve ligation.