Specific effects of idazoxan in a distraction task: evidence that endogenous norepinephrine plays a role in selective attention in rats.

Rats were injected with the alpha 2-adrenergic antagonist idazoxan (IDZ) prior to testing on vigilance and distraction tasks. In the vigilance task, rats responded with nose pokes to brief visual cues presented at variable intervals following trial onset. The distraction task was similar except that irrelevant odor cues (distractors) were presented in the interval prior to light onset on some trials. IDZ injection had no effect on performance in the vigilance task. In the distraction task, however, the higher IDZ dose (1.0 mg/kg) modulated the propensity to make a premature response when the distractors were presented. Notably, the direction of the effect varied with the rats' baseline level of distractibility. This pattern of effects suggests that endogenous norepinephrine (NE) influences distractibility and/or selective attention.