Changes in the behavioral response to a novel environment following lesioning of the central dopaminergic system in rat pups.

During the third week of life, a hyperactive period for laboratory rat, the occurrence of 8 behavioral categories was recorded in individual littermates transferred to a novel environment. Neonatal destruction of the catecholaminergic system by intraventricular injection of 6-OH-DA resulted in increased motor activity during the third week of life. Selective lesioning of the dopaminergic system by the combined treatment of 6-OH-DA + desmethylimipramine also induced a significant increase in some active behavioral categories. It appeared that in contrasts to the gross behavioral sequence, as seen in controls, which compromised locomotion and rearing leads to grooming leads to sitting and lying down, the lesioned animals showed a prolonged phse of restless locomotion. These data are interpreted as a disability to habituate adequately to a novel environment after neonatal lesioning of the dopaminergic system.