1 Although cholecystokinin octapeptide sulphate (CCK-8) activates the opioid system of isolated guinea-pig ileum (GPI) whether it activates the mu- or kappa-system, or both, remains unclear. Neither is it known whether CCK-8 influences the withdrawal responses in GPI preparations briefly exposed to opioid agonists. This study was designed to clarify whether CCK-8 activates mu- or kappa-opioid systems or both; and to investigate its effect on the withdrawal contractures in GPI exposed to mu- or kappa-agonists and on the development of tolerance to the withdrawal response. 2 In GPI exposed to CCK-8, the selective kappa-antagonist nor-binaltorphimine elicited contractile responses that were concentration-related to CCK-8 whereas the selective mu-antagonist cyprodime did not. 3 In GPI preparations briefly exposed to the selective mu-agonist, dermorphin, or the selective kappa-agonist, U-50, 488H, and then challenged with naloxone, CCK-8 strongly enhanced the withdrawal contractures. 4 During repeated opioid agonist/CCK-8/opioid antagonist tests tolerance to opioid-induced withdrawal responses did not develop. 5 These results show that CCK-8 preferentially activates the GPI kappa-opioid system and antagonizes the mechanism(s) that control the expression of acute dependence in the GPI.
Interactions between cholecystokinin and opioids in the isolated guinea-pig ileum / Romanelli, Luca; Maria Carmela, Amico; Francesca, Mattioli; Luigi Antonio, Morrone; Valeri, Pacifico. - In: BRITISH JOURNAL OF PHARMACOLOGY. - ISSN 0007-1188. - ELETTRONICO. - 127:4(1999), pp. 909-918. [10.1038/sj.bjp.0702621]
Interactions between cholecystokinin and opioids in the isolated guinea-pig ileum
ROMANELLI, LUCA;VALERI, Pacifico
1999
Abstract
1 Although cholecystokinin octapeptide sulphate (CCK-8) activates the opioid system of isolated guinea-pig ileum (GPI) whether it activates the mu- or kappa-system, or both, remains unclear. Neither is it known whether CCK-8 influences the withdrawal responses in GPI preparations briefly exposed to opioid agonists. This study was designed to clarify whether CCK-8 activates mu- or kappa-opioid systems or both; and to investigate its effect on the withdrawal contractures in GPI exposed to mu- or kappa-agonists and on the development of tolerance to the withdrawal response. 2 In GPI exposed to CCK-8, the selective kappa-antagonist nor-binaltorphimine elicited contractile responses that were concentration-related to CCK-8 whereas the selective mu-antagonist cyprodime did not. 3 In GPI preparations briefly exposed to the selective mu-agonist, dermorphin, or the selective kappa-agonist, U-50, 488H, and then challenged with naloxone, CCK-8 strongly enhanced the withdrawal contractures. 4 During repeated opioid agonist/CCK-8/opioid antagonist tests tolerance to opioid-induced withdrawal responses did not develop. 5 These results show that CCK-8 preferentially activates the GPI kappa-opioid system and antagonizes the mechanism(s) that control the expression of acute dependence in the GPI.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.