Behavioral differences between outbred Wistar, inbred Fischer 344, brown Norway, and hybrid Fischer 344 x brown Norway rats.

Age differences in cognition have been found in many learning and memory tasks. These age-related cognitive deficits are at least partially caused by pathologic changes that accompany aging. Therefore, it might be advantageous to select a particular rat strain to study the age-associated decrements in cognitive performance. This strain should show "healthy" aging, and its age-related pathologies should be well documented. In the present study we evaluated the behavior of adult Wistar (WIS), Fischer-344 (F344), Brown Norway (BN), and the F1 (F344 x BN) hybrids in a series of tests that assess different aspects of the behavioral domain of rats. Knowledge of the behavioral characteristics of adult rats of these strains and the F1 hybrid may provide relevant information for studies that seek to evaluate the age-related changes in behavior in rats. This also applies to psychobiological studies in general when using rats as experimental subjects. Learning and memory performance was assessed using a Morris water escape task, an inhibitory or passive avoidance task, a delayed nonmatching to position task, and an active avoidance task in a shuttle box. Noncognitive behavior was measured in a shock sensitivity test, a light-dark preference test in a circular light-dark alley, and an open field test. Profound strain differences in cognitive performance and noncognitive behavior were observed. Adult BN rats showed very poor performance in most of the learning tasks. This might restrict their applicability in aging research when age-related deficits in cognitive functions are investigated. It is concluded that the F344 rats and the F344 x BN hybrids appear to be suitable models for aging research, provided special measures are taken to reduce the occurrence of specific pathologies, which are well documented for both genotypes. In addition, if both genotypes are used, a broad range of behavioral test paradigms can be applied in aging studies.