Time course of certain behavioral changes after hippocampal damage and their alteration by dopaminergic intervention into nucleus accumbens.

Independent groups of rats with hippocampal, neocortical, or sham lesions were observed 7, 14, or 28 days after surgery in an open field-hole board apparatus and in a smaller circular apparatus. In the circular apparatus, animals were observed after unilateral injection of the dopamine agonist, 3,4-dihydroxyphenylamino-2-imidazoline (DPI) or saline into nucleus accumbens. Behavioral changes in locomotion, exploration and grooming measured in the open field were consistent with those found previously after hippocampal damage, with each behavioral anomaly demonstrating a specific pattern of change after surgery. In general, the injection of DPI into nucleus accumbens produced greater behavioral change in animals with hippocampal damage than in animals with either neocortical or sham lesions. The drug-induced changes in the hippocampally lesioned rats made their behavior more like that of control animals. These results suggest that destruction of the hippocampus may induce alterations in dopaminergic mechanisms in nucleus accumbens which can be modified by appropriate pharmacologic intervention.