Na⁺, K⁺-ATPase inhibition causes hyperactivity and impulsivity in mice via dopamine D2 receptor-mediated mechanism

Hyperactivity and impulsivity are common symptoms in several psychiatric disorders. Although dysfunction of Na⁺, K⁺-ATPase has been reported to be associated with the psychiatric disorders, it is not clear whether inhibition of Na⁺, K⁺-ATPase causes behavioral effects, including hyperactivity and impulsivity, in mice. Here, we evaluated the effect of intracerebroventricular (icv) injection of ouabain, an inhibitor of Na⁺, K⁺-ATPase, on hyperactivity and impulsivity in mice. At seven days after icv injection, ouabain-injected mice displayed the increase in the distance traveled in the open field arena in the open field test and the increase in the number of head-dipping behavior in the cliff avoidance test. Chlorpromazine or haloperidol, typical antipsychotics, reduced the hyperactivity and impulsivity in ouabain-injected mice. On the other hand, neither lithium carbonate nor valproate, established mood-stabilizing drugs, improved hyperactivity and impulsivity in our mouse model. Furthermore, ouabain-injected mice exhibited the increase in the number of c-fos-positive cells in the nucleus accumbens and the prefrontal cortex but not in the ventral tegmental area, which was reduced by haloperidol. These results suggest that the dysfunction of Na⁺, K⁺-ATPase causes hyperactivity and impulsivity via hyperactivation of dopamine D2 receptor-mediated signaling pathway, causing disturbed neuronal circuits in mice.