Dopamine transporter knockdown mice in the behavioral pattern monitor: A robust, reproducible model for mania-relevant behaviors

Efforts to replicate results from both basic and clinical models have highlighted problems with reproducibility in science. In psychiatry, reproducibility issues are compounded because the complex behavioral syndromes make many disorders challenging to model. We develop translatable tasks that quantitatively measure psychiatry-relevant behaviors across species. The behavioral pattern monitor (BPM) was designed to analyze exploratory behaviors, which are altered in patients with bipolar disorder (BD), especially during mania episodes. We have repeatedly assessed the behavioral effects of reduced dopamine transporter (DAT) expression in the BPM using a DAT knockdown (KD) mouse line (~10% normal expression). DAT KD mice exhibit a profile in the BPM consistent with acutely manic BD patients in the human version of the task-hyperactivity, increased exploratory behavior, and reduced spatial d (Perry et al., 2009). We collected data from multiple DAT KD BPM experiments in our laboratory to assess the reproducibility of behavioral outcomes across experiments. The four outcomes analyzed were: 1) transitions (amount of locomotor activity); 2) rearings (exploratory activity); 3) holepokes (exploratory activity); and 4) spatial d (geometrical pattern of locomotor activity). By comparing DAT KD mice to wildtype (WT) littermates in every experiment, we calculated effect sizes for each of the four outcomes and then calculated a mean effect size using a random effects model. DAT KD mice exhibited robust, reproducible changes in each of the four outcomes, including increased transitions, rearings, and holepokes, and reduced spatial d, vs. WT littermates. Our results demonstrate that the DAT KD mouse line in the BPM is a consistent, reproducible model of mania-relevant behaviors. More work must be done to assess reproducibility of behavioral outcomes across experiments in order to advance the field of psychiatry and develop more effective therapeutics for patients.