Regional brain metabolism during alcohol intoxication

Area of Science:

• Neuroscience
• Pharmacology
• Brain Imaging

Background:

• Ethanol exerts broad effects on neurotransmitter systems, notably facilitating gamma-aminobutyric acid (GABA) neurotransmission through the benzodiazepine/GABA receptor complex.
• This interaction underlies ethanol's depressant effects in the brain.
• Benzodiazepines like lorazepam also enhance GABA neurotransmission.

Purpose of the Study:

• To evaluate the effects of ethanol on regional brain metabolism in healthy men.
• To compare ethanol's effects on brain metabolism with those of lorazepam, a known GABA-enhancing drug.

Main Methods:

• Ten healthy men underwent positron emission tomography (PET) scans using [F-18] fluorodeoxyglucose twice.
• Scans were performed after placebo or ethanol (0.75 g/kg) administration.
• Data were analyzed using region of interest and statistical parametric mapping (SPM) to compare ethanol's effects with previously published lorazepam data.

Main Results:

• Ethanol significantly decreased whole brain metabolism (-25%) and regional metabolism.
• Relative metabolic activity decreased in the occipital cortex and increased in the left temporal cortex and left basal ganglia.
• SPM analyses and comparison with lorazepam data revealed similar patterns, though lorazepam also decreased thalamic metabolism, unlike ethanol.

Conclusions:

• Alcohol and benzodiazepines share similar mechanisms influencing brain glucose metabolism via GABA pathways.
• The reduction in thalamic metabolism by lorazepam, but not ethanol, may explain lorazepam's greater sedative effects.
• Findings support overlapping yet distinct neurobiological effects of ethanol and benzodiazepines.