Striatal presynaptic dopamine function in type 1 alcoholics measured with positron emission tomography

Area of Science:

• Neuroscience
• Psychiatry
• Radiochemistry

Background:

• Previous studies indicated reduced dopamine D2 receptor and transporter densities in late-onset (type 1) alcoholics.
• The hypothesis posited lower striatal presynaptic dopamine function in type 1 alcoholics.

Purpose of the Study:

• To investigate striatal presynaptic dopamine function in type 1 alcoholics using 6-[18F]-FDOPA uptake.
• To determine if dopamine function is decreased in alcoholics compared to controls.

Main Methods:

• Positron emission tomography (PET) imaging with 6-[18F]-FDOPA was used to measure dopamine uptake.
• 10 type 1 alcoholics and 8 matched controls were studied.
• Wisconsin Card Sorting Test (WCST) was administered to assess cognitive function.

Main Results:

• Contrary to the hypothesis, alcoholics exhibited higher mean striatal 6-[18F]-FDOPA uptake than controls, particularly in the left putamen (28% higher) and right caudate (36% higher).
• Elevated uptake in these regions correlated with poorer performance on the WCST, indicating impaired behavioral modification.
• Two patients showed markedly low uptake in the left caudate, suggesting potential heterogeneity within type 1 alcoholism.

Conclusions:

• Type 1 alcoholism is characterized by increased, not decreased, striatal presynaptic dopamine function, possibly as a compensatory response.
• The observed alterations in dopamine function correlate with cognitive deficits in behavioral control.
• Type 1 alcoholism may represent a heterogeneous disorder with varying patterns of presynaptic dopamine dysfunction.