The availability of striatal dopamine transporter (DAT) is increased in bipolar disorder patients compared with healthy individuals, even in patients in the euthymic state, the results of a Taiwanese study indicate.

DAT activity is thought to reflect the general state of dopamine function in the brain, and previous research has shown that euthymic bipolar disorder patients have regions of abnormal brain activation.

To investigate striatal DAT availability in bipolar disorder, Yen Kuang Yang, from National Cheng Kung University Hospital in Tainan, and colleagues used single photon emission computed tomography (SPECT) with [^99mTc] TRODAT-1 to approximate DAT availability in 17 drug-free euthymic bipolar disorder patients and 17 healthy controls matched for age, gender, and education level.

The team reports in the journal Bipolar Disorders that there was no correlation between the DAT ratio and the duration of bipolar disorder, number of manic episodes, or number of depressive episodes.

Patients were found to have a significantly higher binding availability of DAT in the striatum than healthy controls, at an average effect size of 1.04. There were no significant differences in DAT availability between the seven patients with bipolar I disorder and the 10 with bipolar II disorder.

While noting that the study has several limitations, the team concludes: “The present results suggest that an upregulation of DAT may be the primary alteration which progressively leads to lowered intrasynaptic dopamine concentration and then influences the emotional process and cognition in euthymic bipolar patients.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

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