Hippocampal Morphology and Open-Field Behavior in Mus musculus domesticus and Mus spretus Inbred Mice

Mus spretus is extensively used in interspecific mouse backcross analyses employed to generate genetic linkage maps. However, little is known about its behavior and neuroanatomy, phenotypes for which large interstrain differences have been observed in Mus musculus domesticus. Behavioral and hippocampai neuroanatomical variables were measured in adult male mice from the inbred strains C57BL/6J (Mus musculus domesticus) and SEG (Mus spretus). Clear differences were found for behavioral responses to novelty in an open field, SEG being much less active than C57BL/6J. Morphometrical analysis of hippocampai terminal fields, visualized with Timm's stain, revealed strain differences only for the size of the intra- and infrapyramidal mossy fiber terminal fields, which were about 3× larger in C57BL/6J than in SEG. In addition, absolute left-right differences were larger in SEG for the stratum radiatum and stratum oriens. In spite of these behavioral and neuroanatomical differences, the phenotypical scores obtained for SEG do not exceed the range observed for Mus musculus domesticus inbred strains.