Behavioral characteristics of dopamine D5 receptor knockout mice

<jats:title>Abstract</jats:title><jats:p>Major psychiatric disorders such as attention-deficit/hyperactivity disorder and schizophrenia are often accompanied by elevated impulsivity. However, anti-impulsive drug treatments are still limited. To explore a novel molecular target, we examined the role of dopamine D<jats:sub>5</jats:sub> receptors in impulse control using mice that completely lack D<jats:sub>5</jats:sub> receptors (D5KO mice). We also measured spontaneous activity and learning/memory ability because these deficits could confound the assessment of impulsivity. We found small but significant effects of D<jats:sub>5</jats:sub> receptor knockout on home cage activity only at specific times of the day. In addition, an analysis using the q-learning model revealed that D5KO mice displayed lower behavioral adjustment after impulsive actions. However, our results also showed that baseline impulsive actions and the effects of an anti-impulsive drug in D5KO mice were comparable to those in wild-type littermates. Moreover, unlike previous studies that used other D<jats:sub>5</jats:sub> receptor-deficient mouse lines, we did not observe reductions in locomotor activity, working memory deficits, or severe learning deficits in our line of D5KO mice. These findings demonstrate that D<jats:sub>5</jats:sub> receptors are dispensable for impulse control. Our results also indicate that time series analysis and detailed analysis of the learning process are necessary to clarify the behavioral functions of D<jats:sub>5</jats:sub> receptors.</jats:p>