title: Morphine inhibits calcium influx and the response to acetylcholine in Xenopus oocytes.
abstract: Incubation of intact Xenopus oocytes with the opioid radioligand [3H]diprenorphine (0.5 nM) resulted in specific binding of 1.7 +/- 0.3 fmol per oocyte. Morphine (10 microM) inhibited the uptake of 45Ca2+ into the oocyte by 66 +/- 9%. The opioid antagonist naltrexone partially blocked this effect of morphine. Preincubation of oocytes with morphine (10 microM, 2 min) partially inhibited the fast and slow responses of the oocyte to acetylcholine by 26 and 52%, respectively. We conclude that native Xenopus oocytes possess opioid receptors that may modulate the muscarinic response by limiting calcium influx into the cell.
authors.affiliation: Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel.
authors.forename: D
authors.initials: D
authors.lastname: Lipinsky
authors.forename: Y
authors.initials: Y
authors.lastname: Oron
authors.forename: Y
authors.initials: Y
authors.lastname: Sarne
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004174:Diprenorphine / Q000378:metabolism; D004594:Electrophysiology; D005260:Female; D009020:Morphine / Q000494:pharmacology*; D009116:Muscarine / Q000378:metabolism; D009271:Naltrexone / Q000494:pharmacology; D009865:Oocytes / Q000378:metabolism*; D011869:Radioligand Assay; D014982:Xenopus laevis / Q000378:metabolism* / Q000502:physiology
chemical_list: D004174:Diprenorphine; D009271:Naltrexone; D009020:Morphine; D009116:Muscarine; D000109:Acetylcholine; D002118:Calcium