title: Morphine withdrawal in cortical slices: suppression by Ca2+-channel inhibitors of abstinence-induced [3H]-noradrenaline release.
abstract: 1. The effects of morphine withdrawal were evaluated in vitro by monitoring the actions of naloxone on the depolarization-induced release of [3H]-noradrenaline (NA) in cortical slices taken from naïve or dependent rats. The effects of dihydropyridine molecules acting on Ca2+-channels (nimodipine and Bay K 8644) were also studied in this model. 2. Naloxone (10(-8)-10(-5) M) dose-dependently enhanced the K+ induced release of [3H]-NA in slices taken from dependent rats, but failed to modify the [3H]-NA release from 'naïve' slices. 3. The naloxone-induced potentiation of release was significantly reversed by nimodipine (10(-8)-10(-6) M). These doses of nimodipine did not change [3H]-NA release (both basal and K+ induced) in preparations obtained from naïve rats. 4. Bay K 8644 potentiated the K+-induced [3H]-NA release from cortical slices taken from naïve rats to a similar extent as that of naloxone in dependent rats. 5. These results suggest that the naloxone potentiation of the depolarization-induced [3H]-NA release in slices taken from dependent rats may be considered a model of morphine withdrawal in vitro. In this model dihydropyridine Ca2+-channel antagonists suppress morphine-withdrawal effects in a similar manner to observations made in vivo.
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002540:Cerebral Cortex / Q000378:metabolism*; D004095:Dihydropyridines / Q000494:pharmacology; D004195:Disease Models, Animal; D066298:In Vitro Techniques; D007473:Ion Channels / Q000187:drug effects*; D009020:Morphine / Q000009:adverse effects*; D009270:Naloxone / Q000494:pharmacology; D009553:Nimodipine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D013375:Substance Withdrawal Syndrome / Q000378:metabolism*; D014316:Tritium
chemical_list: D004095:Dihydropyridines; D007473:Ion Channels; D014316:Tritium; D009270:Naloxone; D009553:Nimodipine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D009020:Morphine; C038806:1,4-dihydropyridine; D002118:Calcium; D009638:Norepinephrine