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 (I DZ) prior to testing on vigilance and distraction tasks. In the vigila nce task, rats responded with nose pokes to brief visual cues presente d at variable intervals following trial onset. The distraction task wa s similar except that irrelevant odor cues (distractors) were presente d in the interval prior to light onset on some trials. IDZ injection h ad no effect on performance in the vigilance task. In the distraction task, however, the higher IDZ dose (1.0 mg/kg) modulated the propensit y to make a premature response when the distracters were presented. No tably, the direction of the effect varied with the rats' baseline leve l of distractibility. This pattern of effects suggests that endogenous norepinephrine (NE) influences distractibility and/or selective atten tion.