Selective improvement of strain-dependent performances of cognitive tasks by food restriction.

Temporary food restriction affects strain differences for behavioral phenotypes in the inbred strains of mice C57BL/6 (C57) and DBA/2 (DBA). Since food restriction is a routine procedure to motivate learning, we evaluated its influence on differences for spatial and non-spatial discrimination between these strains of mice by using two non-associative tasks: the Spatial Novelty Test (SNT) and the Spontaneous Object Recognition Test (SORT). The results confirmed the poor performance of the DBA mice in SNT. Nonetheless, DBA mice were perfectly able to recognize the novel object in SORT. By contrast, C57 mice were good performers in SNT but failed to recognize a novel object in SORT. Finally, food restriction selectively improved C57 performance in SNT and DBA performance in SORT. These results support the view that a food restricting procedure enhances strain differences for discrimination of configurational information.

Susceptibility to amphetamine-induced place preference is predicted by locomotor response to novelty and amphetamine in the mouse.

RATIONALE: It has been demonstrated that major differences between mice of the C57BL/6J and DBA/2J inbred strains for amphetamine-induced place conditioning (preference and avoidance, respectively) are evident in standard housing conditions but abolished by temporary restricted feeding. This gene-experience model may be usefully exploited to dissect behavioral phenotypes related to place conditioning induced by addictive drugs. OBJECTIVES: This study evaluated a number of behavioral phenotypes related to amphetamine-induced place preference for strain differences (C57BL/6J vs DBA/2J) susceptible to be abolished by temporary food restriction. METHODS: Mice of the two inbred strains were tested for: (1) conditioned taste aversion and place preference induced by amphetamine within the same dose-range; (2) preference for a novel compartment 24 h after a single exposure to only one of two compartments; (3) amphetamine-induced behavioral sensitization and conditioned hyperactivity; and (4) locomotor activity during exploration of a novel environment. RESULTS: The two strains showed consistent taste aversion at doses of amphetamine that promoted opposite strain-dependent place conditioning. Both strains spent more time exploring the novel rather than the known compartment of the place conditioning apparatus. Instead, only mice of the C57 strain showed amphetamine-induced behavioral sensitization and conditioned hyperactivity. However, temporary food restriction did not affect strain differences for these phenotypes. Finally, C57 mice were more active than DBA in a novel environment and restricted feeding abolished this strain-dependent difference. CONCLUSIONS: These results relate individual differences for amphetamine-induced place conditioning with locomotor response to amphetamine and novelty.