Abstract
Bipolar Disorder (BD) is a neuropsychiatric disorder characterized by symptoms ranging from a hyperactive manic state to depression, with periods of relative stability, known as euthymia, in between. Although prognosis for BD sufferers remains poor, treatment development has been restricted due to a paucity of validated animal models. Moreover, most models focus on the manic state of BD with little done to characterize the longitudinal behavior of these models. We recently presented two dopamine transporter (DAT) mouse models of BD mania: genetic (DAT knockdown; KD, mice) and pharmacological (the selective DAT inhibitor GBR 12909). These models exhibit an exploratory profile consistent with the quantified exploratory profile of manic BD patients observed in the cross-species translational test, the Behavioral Pattern Monitor (BPM). To further explore the suitability of these models, we examined the effects of reduced DAT function on the behavior of mice tested after familiarization to the BPM environment. Testing with 16mg/kg GBR 12909 in familiarized mice resulted in a consistent mania-like profile. In contrast, the mania-like profile of DAT KD mice disappears in a familiar environment, with partial reinstatement elicited by the introduction of novelty. In addition, we found that a subthreshold dose of GBR 12909 (9mg/kg) reinstated the mania-like profile in DAT KD mice without affecting wildtype behavior. Thus, the mania-like exploratory profile of DAT KD mice is reduced in a familiar environment, partially reinstated with novelty, but is fully restored when administered a stimulant that is ineffective in wildtype mice. These mice may provide a model of BD from mania to euthymia and back again with stimulant treatment. Acute blockade of the DAT by GBR 12909 however, may provide a consistent model for BD mania.