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Brain dopamine response in human opioid addiction
Mark R C Daglish1, Tim M Williams, Sue J Wilson
1Psychopharmacology Unit, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol, UK.
Summary
Opioid drugs like heroin and hydromorphone did not increase dopamine levels in the brain, despite causing significant subjective effects in study participants. This challenges the role of dopamine in opioid addiction and subjective experiences.
Area of Science:
- Neuroscience
- Addiction Research
- Pharmacology
Background:
- Drugs of dependence, including stimulants, are known to increase dopamine release in the human brain.
- Dopamine plays a crucial role in reward pathways and is implicated in addiction.
Purpose of the Study:
- To investigate whether opioid agonists provoke dopamine release in the brain.
- To examine the relationship between opioid-induced dopamine release and the subjective experience in humans.
Main Methods:
- Two combined positron emission tomography (PET) studies were conducted.
- Fourteen participants on methadone maintenance treatment received placebo and either diamorphine or hydromorphone.
- Brain scans utilized [(11)C]-raclopride to measure dopamine D2 receptor availability.
Main Results:
- Both diamorphine and hydromorphone induced significant subjective and physiological effects.
- No measurable change in [(11)C]-raclopride binding was observed, indicating no significant dopamine release.
Conclusions:
- The absence of a dopamine response to opioids contrasts with findings for stimulant drugs.
- Dopamine may not play the same role in opioid addiction as it does in stimulant addiction.
- The study questions the direct involvement of dopamine in the subjective experience of heroin and other opioids.
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