Morphine preconditions Purkinje cells against cell death under in vitro simulated ischemia-reperfusion conditions.
BACKGROUND
Morphine pretreatment via activation of delta1-opioid receptors induces cardioprotection. In this study, the authors determined whether morphine preconditioning induces ischemic tolerance in neurons.


METHODS
Cerebellar brain slices from adult Sprague-Dawley rats were incubated with morphine at 0.1-10 microM in the presence or absence of various antagonists for 30 min. They were then kept in morphine- and antagonist-free buffer for 30 min before they were subjected to simulated ischemia (oxygen-glucose deprivation) for 20 min. After being recovered in oxygenated artificial cerebrospinal fluid for 5 h, they were fixed for morphologic examination to determine the percentage of undamaged Purkinje cells.


RESULTS
The survival rate of Purkinje cells was significantly higher in slices preconditioned with morphine (> or = 0.3 microM) before the oxygen-glucose deprivation (57 +/- 4% at 0.3 microM morphine) than that of the oxygen-glucose deprivation alone (39 +/- 3%, P < 0.05). This morphine preconditioning-induced neuroprotection was abolished by naloxone, a non-type-selective opioid receptor antagonist, by naltrindole, a selective delta-opioid receptor antagonist, or by 7-benzylidenenaltrexone, a selective delta1-opioid receptor antagonist. However, the effects were not blocked by the mu-, kappa-, or delta2-opioid receptor antagonists, beta-funaltrexamine, nor-binaltorphimine, or naltriben, respectively. Morphine preconditioning-induced neuroprotection was partially blocked by the selective mitochondrial adenosine triphosphate-sensitive potassium channel antagonist, 5-hydroxydecanoate, or the mitochondrial electron transport inhibitor, myxothiazol. None of the inhibitors used in this study alone affected the simulated ischemia-induced neuronal death.


CONCLUSIONS
These data suggest that morphine preconditioning is neuroprotective. This neuroprotection may be delta1-opioid receptor dependent and may involve mitochondrial adenosine triphosphate-sensitive potassium channel activation and free radical production. Because morphine is a commonly used analgesic, morphine preconditioning may be explored further for potential clinical use to reduce ischemic brain injury.
Lim
Young Jin
YJ
Department of Anesthesiology, University of Virginia Health System, Charlottesville 22908-0710, USA.
Zheng
Shuqiu
S
Zuo
Zhiyi
Z
D000818:Animals; D016923:Cell Death / Q000187:drug effects; D002531:Cerebellum / Q000473:pathology; D004305:Dose-Response Relationship, Drug; D004579:Electron Transport / Q000187:drug effects; D005947:Glucose / Q000502:physiology; D000860:Hypoxia / Q000473:pathology; D066298:In Vitro Techniques; D019194:Ischemic Preconditioning; D008297:Male; D008565:Membrane Proteins / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism; D009020:Morphine / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D018696:Neuroprotective Agents; D015221:Potassium Channels; D011689:Purkinje Cells / Q000187:drug effects*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017465:Receptors, Opioid, delta / Q000187:drug effects; D015427:Reperfusion Injury / Q000473:pathology*
D008565:Membrane Proteins; D009292:Narcotic Antagonists; D009294:Narcotics; D018696:Neuroprotective Agents; D015221:Potassium Channels; D017465:Receptors, Opioid, delta; C117780:mitochondrial K(ATP) channel; D009020:Morphine; D005947:Glucose