Aberrant extracellular dopamine clearance in the prefrontal cortex exhibits ADHD-like behavior in NCX3 heterozygous mice.

Attention-deficit/hyperactivity disorder (ADHD) is a neurodevelopmental disorder that involves dopaminergic dysfunction in the prefrontal cortex (PFC), manifesting hyperactivity, inattention, and cognitive deficits. However, the ADHD-associated candidate genes underlying dopaminergic neurotransmission alterations remain poorly defined. Here, we identified the abundant localization of sodium-calcium exchanger 3 (NCX3) levels in the dopaminergic neurons of the ventral tegmental area, a major source of dopaminergic innervation to the PFC. We confirmed that NCX3 knockdown in N27 cells caused aberrant dopamine influx through the strong interaction between calcium/calmodulin-dependent protein kinase II alpha and dopamine transporter. In addition, we assessed behavioral changes and underlying molecular properties in NCX3 heterozygous (NCX3) mice. NCX3 mice exhibited hyperactivity, cognitive deficits, and social dysfunction which were alleviated by treating with methylphenidate. Furthermore, NCX3 mice displayed a persistent elevation of basal dopamine levels and decreased extracellular levels of dopamine triggered by social stimuli in the PFC of NCX3 mice. In agreement with the rise in extracellular dopamine levels in the PFC, NCX3 mice showed activation of dopamine D1 receptor signaling pathways in the PFC compared to wild-type mice. Thus, deficiency of NCX3 leads to impaired dopaminergic neurotransmission in the PFC, which likely accounts for the ADHD-like behavior in NCX3 mice.