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Background Atomoxetine is commonly used for the treatment of attention deficit hyperactivity disorder,which could increase noradrenalin levels while activate dopamine transporter at a higher dose.It has been suggested that there may some interaction between noradrenalin and dopamine caused by atomoxetine when moderate impulsivity.Thus,we examined the effects of acute atomoxetine,haloperidol and their co-administration on impulsivity with a new impulsive model in rats.Methods The effects of atomoxetine(0.1 – 3.0 mg/kg),DA antagonist haloperidol(0.025-0.1 mg/kg)and co-administration of atomoxetine(0.3 mg/kg)and haloperidol(0.025 mg/kg and 0.05 mg/kg)were evaluated on a new impulsive model,namely response inhibition-delay discounting task,which can assess impulsive action and impulsive choice simultaneously.Rats in this procedure should make a choice between two levers,one is a small immediate(1 Food pellet)reward and another is a large but delayed reward(3 Food pellets),and the delayed time is increasing across block(i.e.,0 s-5 s-10 s-20 s).In addition,rats should acquire a response inhibition task before they make a choice,they should pay attention to the light cues,if they press any lever before the lights illuminated(waiting time is 4 s),it is recorded as a premature response,and will lead to an inter-trial interval(ITI)time and another trial begins.Results Atomoxetine had a dose dependent effect on impulsive choice and impulsive action,with 0.3 mg/kg increased the proportion for large-delayed rewards yet decreased it in 3.0 mg/kg,and 0.3 mg/kg increased the premature frequencies yet left it intact in in 3.0 mg/kg.Although,haloperidol(0.025 mg/kg,0.05 mg/kg and 0.1 mg/kg)had no effect on impulsivity,it increased the latency and omission in RIDDT dose dependently.Finally,the co-administration of atomoxetine(0.3 mg/kg)and haloperidol(0.025 mg/kg and 0.05 mg/kg)had no effects on impulsivity but still affected latency and omission at the dose of 0.05 mg/kg with haloperidol.Conclusion low-dose of atomoxetine executes a contrary effect on impulsivity,increasing impulsive action yet decreasing impulsive choice at the same time.Atomoxetine also produces an inverted-U dose-dependent curve in impulsive choice.Haloperidol can be used to disentangle the contrary effects of atomoxetine(low dose).These data conclusively suggest that dopamine is involved in the moderation of atomoxetine in impulsivity.