Reactions to spatial and nonspatial change in two inbred strains of mice: Further evidence supporting the hippocampal dysfunction hypothesis in the DBA/2 strain

Mice belonging to the inbred C57BL/6 and DBA/2 strains were repeatedly exposed to a given spatial configuration of five objects contained in an open field. Locomotor activity, habituation of exploration, and reactivity to the displacement of some objects (spatial change) and to the substitution of a familiar object by a new one (nonspatial change) were examined. The results show that DBA mice were more active than C57 mice and that habituation developed more rapidly in the former strain. DBA mice did not react to spatial change by an increased exploration directed toward the displaced objects, whereas C57 mice showed both an increased interest for these objects and a parallel decreased interest for the nondisplaced ones. Conversely, both strains strongly reacted to non-spatial change. These results support the hypothesis that DBA mice represent a genetic model of hippocampal dysfunction. The fact that, in these and other spatial tasks, DBA mice behave as rats with dorsal lesions of the hippocampus suggests that mice from this strain reproduce more specifically the dorsal hippocampal syndrome.