Atomoxetine facilitates attentional set shifting in adolescent rats

Adolescent rats show immaturities in executive function and are less able than adult rats to learn reinforcement reversals and shift attentional set. These two forms of executive function rely on the functional integrity of the orbitofrontal and prelimbic cortices respectively. Drugs used to treat attention deficit disorder, such as atomoxetine, that increase cortical catecholamine levels improve executive functions in humans, non-human primates and adult rats with prefrontal lesions. Cortical noradrenergic systems are some of the last to mature in primates and rats. Moreover, norepinephrine transporters (NET) are higher in juvenile rats than adults. The underdeveloped cortical noradrenergic system and higher number of NET are hypothesized to underlie the immaturities in executive function found in adolescents. We assessed executive function in male Long-Evans rats using an intra-dimensional/extradimensional set shifting task. We administered the NET blocker, atomoxetine (0.0, 0.1, 0.9 mg/kg/ml; i.p.), prior to the test of attentional set shift and a reinforcement reversal. The lowest dose of drug facilitated attentional set shifting but had no effect on reversal learning. These data demonstrate that NET blockade allows adolescent rats to more easily perform attentional set shifting.