1. Oxytocin neurone autoexcitation during morphine withdrawal in anaesthetized rats.
- Author
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Brown CH, Munro G, Johnstone LE, Robson AC, Landgraf R, and Russell JA
- Subjects
- Action Potentials drug effects, Action Potentials physiology, Analysis of Variance, Animals, Cerebral Ventricles drug effects, Female, Injections, Intravenous, Injections, Intraventricular, Microdialysis, Naloxone administration & dosage, Neurons drug effects, Oxytocin blood, Rats, Rats, Sprague-Dawley, Supraoptic Nucleus drug effects, Cerebral Ventricles physiopathology, Morphine Dependence physiopathology, Naloxone pharmacology, Neurons physiology, Oxytocin physiology, Substance Withdrawal Syndrome physiopathology, Supraoptic Nucleus physiopathology
- Abstract
We investigated whether release of oxytocin into the supraoptic nucleus is involved in morphine-withdrawal excitation of oxytocin neurones. Retrodialysis of naloxone into the supraoptic nucleus of morphine-dependent rats increased intranuclear oxytocin release by 56.5p +/- 12.7% whereas no change was seen in vehicle-treated dependent rats. In another experiment, in morphine-dependent rats given intravenous (i.v.) naloxone, intracerebroventricular (i.c.v.) oxytocin receptor antagonist injection reduced the increase of plasma oxytocin concentration (to 28-fold) compared with i.c.v. vehicle (62-fold increase). Finally, the increase in oxytocin neurone firing rate following morphine-withdrawal in the presence of i.c.v. oxytocin antagonist infusion was 28% of the steady state firing rate (15-20 min later) and this was lower (p < 0.05) than the percentage increase in i.c.v. vehicle-infused rats (89%). Thus, central endogenous oxytocin may be involved in withdrawal excitation of oxytocin neurones.
- Published
- 1997
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