The brain requires a balance of chemicals to function properly. When imbalances occur, a person is at risk for physical, as well as a variety of mental, conditions to occur. One disorder related to such imbalances is bipolar disorder. The brain chemical dopamine has been identified as part of the link to causation of bipolar disorder.
Role
Dopamine is a neurotransmitter, a type of brain chemical that affects mood and behavior. It is released by an area of the brain called the hypothalamus, which also regulates other functions such as hunger, thirst and body temperature. Dopamine acts on the central nervous system by increasing blood pressure and heart rate.
Evidence
A study published in December 2009 in "Bipolar Disorders" conducted a critical analysis of the body of research on bipolar disorder and found dopamine may play a major role in the disorder. For example, evidence for pharmacological studies show mania in bipolar disorder is associated with increased dopamine activity, and depression in bipolar disorder is linked to decreased dopamine activity, according to the findings of a study published in October 2007 in "Acta Psychiatrica Scandinavica."
Treatment
Dopamine administered as a drug cannot cross the blood-brain barrier. However, the understanding of the role of dopamine in bipolar depression has spawned the use of atypical antipsychotics to treat bipolar disorder, according to a January 2007 article published in "Progress in Neuro-Psychopharmacology and Biological Psychiatry." Atypical antipsychotics, such as Zyprexa, also known as olanzapine, are a therapeutic class of drugs that have a tranquilizing effect on the central nervous system and can help manage the symptoms of bipolar disorder without triggering unwanted symptoms.
Mechanism
Typical antipsychotics bind more tightly to the dopamine receptor than dopamine itself. This leads to the reduced ability of dopamine to enter the receptor site, according to a study published in 2004 in "Focus." Extrapyramidal signs and symptoms, or movement-related problems, follow as a result of this dopamine restriction. Atypical antipsychotics like Zyprexa bind more loosely to the dopamine receptors, allowing dopamine to flow freely and not exacerbate the symptoms of bipolar disorder.
Predisposition
There is evidence bipolar disorder has a genetic component to it that involves dopamine. Specifically, differences in the SLC6A3 gene have been observed in the offspring of parents with bipolar disorder, according to a study published in October 2008 in the "American Journal of Medical Genetics." SLC6A3 is a protein that helps pump dopamine out of the synaptic gap, or space between neurons, so it can be utilized for normal brain functioning. Genetics can influence how much of this protein SLC6A3 is expressed in an individual, thereby creating potential for a dopamine-related disorder.
References
- Wiley Online Library: "Bipolar Disorders": The Role of Dopamine in Bipolar Disorder
- Wiley Online Library: "American Journal of Medical Genetics": Family Based Association Study of Pediatric Bipolar Disorder and the Dopamine Transporter Gene (SLC6A3)
- Science Direct: "Progress in Neuro-Psychopharmacology and Biological Psychiatry": Atypical Antipsychotics in Bipolar Depression: Neurobiological Basis and Clinical Implications
- "Focus": Atypical Antipsychotics: Mechanism of Action
- Wiley Online Library: "Acta Psychiatrica Scandinavica": Dopamine Dysregulation Syndrome: Implications for a Dopamine Hypothesis of Bipolar Disorder
