OPIOID ANTAGONIST NALOXONE POTENTIATES ANXIOGENIC-LIKE ACTION OF CHOLECYSTOKININ AGONISTS IN ELEVATED PLUS-MAZE

This study investigated the interplay of cholecystokinin (CCK) and end ogenous opioid peptides in the regulation of anxiety. The acute admini stration of non-selective CCK agonist caerulein (1 and 5 mu g/kg) and a selective CCKB receptor agonist BOC-CCK-4 (1, 10 and 50 mu g/kg) ind uced a dose-dependent anxiogenic-like action in the plus-maze model of anxiety. BOC-CCK-4 displayed a similar efficacy with caerulein, indic ating that the described effect was mediated via CCKB receptor subtype . The opioid antagonist naloxone itself (0.5 mg/kg) did not change the exploratory activity of rats in the plus-maze. However, the combinati on of naloxone with the sub-effective doses of caerulein (1 mu g/kg) a nd BOC-CCK-4 (1 mu g/kg) induced a significant inhibition of explorato ry behaviour in rats. Accordingly, CCK and endogenous opioid peptides have an antagonistic role in the exploratory model of anxiety in rats.