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Postmortem changes in rat brain extracellular opioid peptides revealed by microdialysis
N T Maidment1, B Siddall, V D Rudolph
1Department of Psychiatry and Biobehavioral Sciences, UCLA School of Medicine 90024.
Journal of Neurochemistry
|June 1, 1991
Summary
Brain ischemia triggers a rapid release of opioid peptides, specifically Met- and Leu-enkephalin, in the rat globus pallidus. Calcium influx appears to play a role in this response during ischemic events.
Area of Science:
- Neuroscience
- Neurochemistry
Background:
- Extracellular opioid peptides play crucial roles in brain function.
- Terminal brain ischemia is a critical condition affecting neuronal function.
Purpose of the Study:
- To investigate changes in extracellular opioid peptide levels in the rat globus pallidus/ventral pallidum during terminal brain ischemia.
- To elucidate the role of calcium in ischemia-induced opioid peptide release.
Main Methods:
- Microdialysis was employed to sample extracellular fluid in the rat brain.
- Solid-phase radioimmunoassay and High-Performance Liquid Chromatography (HPLC) were used to quantify opioid peptides.
- Ischemia was induced via anesthetic overdose or vascular severance.
Main Results:
- A significant 13-fold increase in extracellular immunoreactivity was observed following anesthetic overdose.
- Perfusion with a calcium-free, EGTA-containing medium attenuated the response to a threefold increase, suggesting calcium's involvement.
- Opioid peptide release was detected within 5 minutes of ischemia onset.
- HPLC analysis identified Met- and Leu-enkephalin as the primary released opioid peptides.
Conclusions:
- Terminal brain ischemia induces a rapid release of Met- and Leu-enkephalin in the globus pallidus/ventral pallidum.
- Calcium influx is implicated in the mechanism of ischemia-induced opioid peptide release.