HIPPOCAMPAL MORPHOLOGY AND OPEN-FIELD BEHAVIOR IN MUS-MUSCULUS-DOMESTICUS AND MUS-SPRETUS INBRED MICE

Mus spretus is extensively used in interspecific mouse backcross analy ses employed to generate genetic linkage maps. However, little is know n about its behavior and neuroanatomy, phenotypes for which large inte rstrain differences have been observed in Mus musculus domesticus. Beh avioral and hippocampal neuroanatomical variables were measured in adu lt male mice from the inbred strains C57BL/6J (Mus musculus domesticus ) and SEG (Mus spretus). Clear differences were found for behavioral r esponses to novelty in an open field, SEG being much less active than C57BL/6J. Morphometrical analysis of hippocampal terminal fields, visu alized with Timm's stain, revealed strain differences only for the siz e of the intra- and infrapyramidal messy fiber terminal fields, which were about 3x larger in C57BL/63 than in SEG. In addition, absolute le ft-right differences were larger in SEG for the stratum radiatum and s tratum oriens. In spite of these behavioral and neuroanatomical differ ences, the phenotypical scores obtained for SEG do not exceed the rang e observed for Mus musculus domesticus inbred strains.