Evidence against a role of the rat's dorsal noradrenergic bundle in selective attention and place memory

In Experiment 1, 6-hydroxydopamine-induced lesions of the dorsal noradrenergic bundle (DNB) in rats did not impair either acquisition of non-delayed alternation, retention of non-delayed alternation, or performance of alternation with delays in a T-maze, whether or not the goal arms of the maze were visually distinctive. These results were in contrast with those of a previous report indicating that DNB lesions impair learning of spatial alternation. In Experiment 2, the lack of a reliable effect of DNB lesions on learning performance of spatial alternation was confirmed. However, the rats with DNB lesions showed an impairment of spontaneous alternation. The negative results of the present study do not support either the hypothesis that depletion of forebrain noradrenaline impairs selective attention or the hypothesis that such depletion induces an amnesia for past places. On the other hand, the finding of impaired spontaneous alternation is consistent with previous observations suggesting that depletion of forebrain noradrenaline impairs habituation of fear reactions.