Failure of dorsal bundle lesions in rats to increase distractibility to a low intensity tone

Bilateral lesions of the dorsal noradrenergic bundle in rat brains with 6-hydroxydopamine produced a depletion of cortical noradrenaline to 19% of control values. Rats so treated showed resistance to extinction of a lever press task but no increased distractability from licking behaviour by a low intensity tone. These results cast doubt on the hypothesis that dorsal noradrenergic bundle lesions cause hyperdistractibility in rats.