Cholecystokinin octapeptide antagonized opioid analgesia mediated by mu- and kappa- but not delta-receptors in the spinal cord of the rat.
Intrathecal (ith) injection of cholecystokinin octapeptide (CCK-8) to the rat with single dose of 4 or 40 ng, or successive doses from 0.1 to 1 microgram at 10 min intervals produced neither analgesia nor hyperalgesia. However, the analgesia produced by ith injection of PL017, a specific mu-receptor agonist or 66A-078, a specific kappa-receptor agonist could be markedly antagonized by CCK-8 at a dose as small as 4 ng. In contrast, analgesia produced by ith injection of delta-agonist DPDPE could not be blocked by CCK-8 even at a dose as high as 40 ng. Since the effect of CCK-8 could be totally reversed by the CCK receptor antagonist proglumide, this effect is most probably mediated by CCK receptors.
Wang
X J
XJ
Department of Physiology, Beijing Medical University, People's Republic of China.
Wang
X H
XH
Han
J S
JS
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000031:analogs & derivatives / Q000494:pharmacology; D004723:Endorphins / Q000494:pharmacology; D020881:Enkephalin, D-Penicillamine (2,5)-; D004745:Enkephalins / Q000494:pharmacology; D008297:Male; D009292:Narcotic Antagonists; D010146:Pain / Q000503:physiopathology; D010147:Pain Measurement; D010446:Peptide Fragments / Q000494:pharmacology; D011377:Proglumide / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D011930:Reaction Time / Q000187:drug effects; D011957:Receptors, Opioid / Q000502:physiology*; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; D012844:Sincalide / Q000494:pharmacology*; D013116:Spinal Cord / Q000502:physiology*
D004723:Endorphins; D004745:Enkephalins; D009292:Narcotic Antagonists; D010446:Peptide Fragments; D011957:Receptors, Opioid; D017465:Receptors, Opioid, delta; D017473:Receptors, Opioid, kappa; D017450:Receptors, Opioid, mu; C061285:E 2078; D004399:Dynorphins; C044708:morphiceptin, N-Me-Phe(3)-; D020881:Enkephalin, D-Penicillamine (2,5)-; D011377:Proglumide; D012844:Sincalide