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Ethanol-induced increase in endogenous dopamine release may involve endogenous opiates
1Department of Biochemistry and Physiology, University of Reading, Berkshire, England.
Journal of Neurochemistry
|July 1, 1992
Summary
Opiate peptides differentially affect dopamine release in the brain. Delta-opioid agonists increase basal dopamine release, while mu- and epsilon-opioid agonists inhibit stimulated release, suggesting complex interactions.
Area of Science:
- Neuroscience
- Pharmacology
- Neurochemistry
Background:
- Endogenous dopamine (DA) plays a crucial role in striatal function.
- Opiate peptides are known to modulate neuronal activity.
- Understanding opiate peptide effects on DA release is key to deciphering neurochemical signaling pathways.
Purpose of the Study:
- To investigate the in vitro effects of various opiate peptides on basal and potassium-stimulated endogenous dopamine release from striatal slices.
- To elucidate the specific roles of delta-, mu-, and epsilon-opioid receptors in modulating dopamine release.
- To examine the influence of ethanol on dopamine release and its potential interaction with the endogenous opiate system.
Main Methods:
- In vitro study using rat striatal slices.
- Measurement of endogenous dopamine release under basal and potassium-stimulated conditions.
- Application of specific delta- (Met5-enkephalin, DADLE, DSLET), mu- (DAGO), and epsilon- (beta-endorphin) opioid receptor agonists.
- Use of naloxone and ICI 174864 as opioid receptor antagonists.
- Addition of ethanol to assess its effects on dopamine release.
Main Results:
- Delta-opioid receptor agonists (Met5-enkephalin, DADLE, DSLET) dose-dependently increased basal dopamine release but did not affect stimulated release.
- Mu- (DAGO) and epsilon- (beta-endorphin) opioid receptor agonists inhibited potassium-stimulated dopamine release without altering basal release.
- Ethanol (75 mM) selectively increased basal dopamine release, an effect inhibited by naloxone and the delta-opioid antagonist ICI 174864, suggesting involvement of endogenous delta-opiate agonists.
Conclusions:
- Opiate peptides exert differential modulatory effects on striatal dopamine release, with distinct actions mediated by delta, mu, and epsilon receptors.
- The observed ethanol-induced increase in basal dopamine release appears to be an indirect effect mediated by the endogenous delta-opiate system.
- These findings highlight the complex interplay between exogenous/endogenous opioids, ethanol, and dopamine neurotransmission in the striatum.