Neonatal monoaminergic depletion in mice (Mus musculus) improves performance of a novel odor discrimination task

This experiment examined behavior and neurochemistry in adult mice (Mus mus culus) after neonatal depletion of monoaminergic fibers projecting to the n eocortex and hippocampus. Lesions were made on Postnatal Day 1; mice develo ped to adulthood and were assessed on simple odor discrimination (SOD) and odor delayed nonmatch-to-sample (DNMS) tasks, passive avoidance (PA), and l ocomotor activity. On SOD, lesioned mice performed faster than controls but with similar accuracy. On the DNMS task, the lesioned mice performed faste r and more accurately than controls. On PA, the lesioned mice exhibited a r etention deficit relative to controls. Locomotor activity was similar in th e 2 groups. Postmortem analyses revealed that the lesions reduced significa ntly norepinephrine and serotonin levels in both the neocortex and hippocam pus. The data suggest that cortically projecting monoaminergic fibers play an important role in normal cognitive development.