Noradrenergic modulation of cognitive function in rat medial prefrontal cortex as measured by attentional set shifting capability.

ABSTRACT

The brain noradrenergic system is thought to facilitate neuronal processes that promote behavioral activation, alertness, and attention. One region in which norepinephrine may exert such effects is the medial prefrontal cortex, which has been implicated in many cognitive functions including arousal, attention, motivation, working memory, response inhibition, and behavioral flexibility. The present study addressed the modulatory influence of noradrenergic neurotransmission in medial prefrontal cortex on cognitive function in rats, as measured by performance in an attentional set shifting task. In experiment 1, we tested effects of increasing and decreasing brain noradrenergic neurotransmission by systemic administration of the alpha2-adrenergic autoreceptor antagonist and agonist drugs, atipamezole and clonidine, respectively. Atipamezole pretreatment significantly improved performance on the stages of the attentional task requiring an extradimensional shift in attention, and those involving stimulus reversals, whereas clonidine had no effect at any stage. In experiment 2, we then tested effects of microinjecting alpha1- or beta-adrenergic receptor antagonists into medial prefrontal cortex on the enhancement of performance on the extradimensional task produced by atipamezole. The atipamezole-induced enhancement of performance on the extradimensional set shifting task was blocked by alpha1-, but not beta-adrenergic receptor antagonists in medial prefrontal cortex. Neither antagonist alone had any effect on extradimensional set shift performance in the absence of atipamezole-induced enhancement. These results indicate that elevating noradrenergic activity at alpha1-receptors in medial prefrontal cortex facilitates cognitive performance of rats in an attentional set-shifting task, which may contribute to the role of norepinephrine in behavioral state changes such as arousal, or to the beneficial cognitive effects of psychotherapeutic drugs that target noradrenergic neurotransmission.