CHOLECYSTOKININ OCTAPEPTIDE(CCK-8)ANTAGONIZED NALGESIA MEDIATED BY MU AND KAPPA OPIOID RECEPTORS
WANG XIAO-HONG;WANG XIAO-JING;HAN JI-SHENG(Department of Physiology,Beijing Medical University)
CCK-8 has been shown to antagonize the analgesia produced by morphine orendogenous opioid peptides.The present study was performed to clarify the in-teraction between CCK-8 and different opioid ligands.Analgesia produced byintrathecal(I.T.)injection of the specific μ receptor agonist PL017 10ng or κreceptor agonist NDAP 500 ng can be antagonized by I.T.injection CCK-8 at adose as small as 4 ng.In contrast,analgesia produced by I.T.injection of the δreceptor agonist DPDPE(6.5,13 and 26μg)was not blocked by CCK-8(4ng or40 ng,I.T.)The antagonistic effect of CCK-8 on PL017 and NDAP could becompletely reversed by proglumide(3μg,I.T.).I.T.injection of CCK-8(4 or 40 ngsingle dose or cummulative dose of 0.1,0.2,0.5 and 1.0 μg at 10 min intervals)pro-duced neither analgesia nor hyperalgesia.In conclusion,CCK-8 prcferentiallyantagonizes opioid analgesia mediated by μand κreceptors,and this antagonisticeffect is mediated by CCK receptors.