MedWire News: The dopaminergic system appears to play a central role in the pathophysiology of bipolar disorder and may point the way to novel treatments, the results of a review indicate.

A comprehensive pathophysiologic model of bipolar disorder is lacking, despite there being effective pharmacologic treatments for the disorder. Nevertheless, several brain regions and neuronal components of the behavioral and cognitive manifestations of bipolar disorder have been recently identified.

To extend knowledge of the role of dopamine in bipolar disorder, David Cousins (Newcastle University, UK) and colleagues conducted a review of behavioral, neurochemical, receptor, imaging, and genetic studies, as well as pharmacologic manipulation studies in comparison with other diseases.

The team writes in the journal Bipolar Disorders that dopaminergic pathways are associated with many areas implicated in the core symptoms of bipolar disorder and other associated conditions and, although mania and depression have been linked to increases and decreases in dopaminergic function, respectively, this model does not fit the clinical pattern.

The role of dopamine in bipolar disorder is supported by studies of pharmacologic interventions, with antimanic agents antagonizing dopaminergic activity and antidepressants commonly increasing such activity, as well as mania treatment leading to depression.

Acknowledging the limitations of such observations, the team says that the clinical manifestations of bipolar disorder have not yet been established as a unified process, and that several distinct processes may underlie the common clinical phenotype. Furthermore, comorbidities complicate the picture.

They also write that receptor occupancy changes in bipolar disorder psychosis point to individual pathway functions in bipolar disorder, despite imaging studies failing to identify consistent abnormalities.

The team concludes: “Dopaminergic mechanisms are likely to play a central role in our understanding of the pathophysiology of bipolar disorder and the development of new treatments.

“As the dopamine model of bipolar disorder continues to develop and is enriched by the findings from the broader field of dopamine neuroscience, a shift from a simple dichotomy of neurotransmitter activity seems inevitable.”

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; 2009

Free abstract