"Of Mice and Mania"

There is a study being done to find the relationship of dopamine production to people with bipolar disorder in a manic episode. It is being conducted by manipulating a gene called the Clock gene in mice which is located in their brain and is associated with dopamine production. The purpose for altering this gene in mice is to find out which genes affect the neurochemical processes in humans related to dopamine.

Mice with the altered Clock gene seemed to respond more to the electric impulses sent to the pleasure pathways of their brain than the unaltered mice. These genetically altered mice kept coming back to the stimulus frequently, and the unaltered mice were not going back as often. When the Clock mice were given a dose of cocaine they were going back to the stimulus like the unaltered mice were, so their usage of the stimulus was reduced by the dose they were given.

Also, when mice were given a choice between water or sugar solution, this is something that mice find rewarding, the genetically altered mice chose the sugar solution more often than the normal unaltered mice. Genetically altered mice mimic symptoms of people in a manic bipolar state; hypersensitivity to rewards and euphoria, hyperactivity and nervous behavior, reduced anxiety and risk taking, mood stabilizing drug addiction.

Eitghty to ninety percent of people with bipolar disorder have a relative with a mood disorder. Clinicians have noted both depression and manic episodes increase substance abuse. This means these people tend to abuse stimulant drugs during manic phase and alcohol during depressive period. The lifetime rate of substance abuse for people with bipolar disorder is 38% where the rate is 10% for people without psychiatric illness. When bipolar patients abuse stimulating drugs their risks for hospitalization and suicide increase.

The genetically altered mice have different neurobiology than normal mice. Neurons in the starting point for brain dopamine pathways, including the reward circuit, fire more frequently and strongly resulting in greater dopamine release. Extra dopamine in the reward pathway is a critical factor in addiction and may influence vulnerability to both drug abuse and manic symptoms. This research is being done to find if the release of extra dopamine is also true in people with bipolar disorder in a manic episode. The findings may also provide clues to new treatments for people with bipolar disorder and drug abuse.

Whitten, Lori. "Manic Mice Show Heightened Sensitivity to Rewards." NIDA Notes Nov. 2009: 9-10. Print.