Bipolar patients with mania had decreased striatum dopamine transporter (DAT) levels, whereas bipolar patients with remitted mania had DAT levels that approximated normal.
Putting It Into Practice
Converging pharmacologic and imaging findings confirm that the manic phase in bipolar patients is characterized by hyperdopaminergia with elevations in D2/D3 receptors. Thus, an increase in striatal D2/D3 receptor availability leads to increased dopaminergic neurotransmission during the manic phase in patients with bipolar disorder.
In contrast, increased dopamine transporter levels lead to a reduction in dopaminergic function and clinical depression.
Why this study matters
The findings of the current study support the dopamine hypothesis in patients with bipolar disorder, and specifically, the increased dopamine levels in the manic phase. Elucidation of the pathophysiologic mechanism underlying bipolar disorder will support the use of D2/D3 receptor blockers and//or agents that decrease dopamine synthesis and release.
This was a cross-sectional study conducted at a tertiary care center. Twenty-six patients with bipolar disorder (current mania, n=9; remitted mania, n=17) and 21 matched controls without bipolar disorder were enrolled.
DAT levels were determined based on positron emission tomography as the non-displaceable binding potential (BPND).
Mania was evaluated using the Young Mania Rating Scale (YMRS).
Results and conclusion
The mean age of the 47 study participants was 37.8 years.
Among patients with current mania, the BPND level was decreased in the right putamen and nucleus accumbens (22%) and the left putamen and caudate (24%).
Among patients with remitted mania, the BPND was decreased in the left striatum only.
The YMRS score correlated with the BPND level in the right striatum in patients with current and remitted mania, but not the left striatum.
Yathman LN, Liddle PF, Gonzalez M, et al. A positron emission tomography study of dopamine transporter density in patients with bipolar disorder with current mania and those with recently remitted mania. JAMA Psychiatry 2022; doi:10.1001/jamapsychiatry.2022.3541.