Impaired cliff avoidance reaction in dopamine transporter knockout mice

Rationale: Impulsivity is a key feature of disorders that include attention-deficit/hyperactivity disorder (ADHD). The cliff avoidance reaction (CAR) assesses maladaptive impulsive rodent behavior. Dopamine transporter knockout (DAT-KO) mice display features of ADHD and are candidates in which to test other impulsive phenotypes. Objectives: Impulsivity of DAT-KO mice was assessed in the CAR paradigm. For comparison, attentional deficits were also assessed in prepulse inhibition (PPI) in which DAT-KO mice have been shown to exhibit impaired sensorimotor gating. Results: DAT-KO mice exhibited a profound CAR impairment compared to wild-type (WT) mice. As expected, DAT-KO mice showed PPI deficits compared to WT mice. Furthermore, the DAT-KO mice with the most impaired CAR exhibited the most severe PPI deficits. Treatment with methylphenidate or nisoxetine ameliorated CAR impairments in DAT-KO mice. Conclusion: These results suggest that DAT-KO mice exhibit impulsive CAR behavior that correlates with their PPI deficits. Blockade of monoamine transporters, especially the norepinephrine transporter (NET) in the prefrontal cortex (PFC), may contribute to pharmacological improvement of impulsivity in these mice.