High ethanol and acetaldehyde decrease extracellular glutamate in the frontal cortex of freely moving mice.

Area of Science:

• Neuroscience
• Pharmacology
• Biochemistry

Background:

• Previous studies showed ethanol (EtOH) and acetaldehyde (AcH) decrease hippocampal glutamate.
• The effect of EtOH and AcH on frontal cortex glutamate remains unclear.

Purpose of the Study:

• Investigate the impact of local EtOH and AcH perfusion on frontal cortex extracellular glutamate.
• Compare these effects in Aldh2-knockout (Aldh2-KO) and wild-type (WT) mice.

Main Methods:

• Local microdialysis perfusion of EtOH and AcH into the frontal cortex of Aldh2-KO and WT mice.
• Measurement of extracellular glutamate using High-Performance Liquid Chromatography (HPLC) with an electrochemical detector.
• Analysis of dose-dependent effects of EtOH (100-500 mM) and AcH (100-500 µM).

Main Results:

• High doses of EtOH (200 and 500 mM) significantly decreased frontal cortex glutamate in both WT and Aldh2-KO mice.
• A greater glutamate decrease was observed in Aldh2-KO mice with 500 mM EtOH, suggesting AcH involvement.
• AcH (200 and 500 µM) decreased glutamate in Aldh2-KO mice but not WT mice, due to efficient AcH oxidation in WT mice.
• Low doses of EtOH (100 mM) and AcH (100 µM) had no significant effect on glutamate levels.

Conclusions:

• High concentrations of EtOH and AcH induce a significant reduction in frontal cortex extracellular glutamate.
• These findings in mice support the hypothesis that decreased glutamate neurotransmission contributes to the central depressant effects of EtOH.
• Aldehyde dehydrogenase 2 (ALDH2) activity influences the impact of AcH on glutamate levels.