Differences in measures of exploration and fear in MHC-congenic C57BL/6J and B6-H-2K mice

MHC-congenic mice prefer to mate with mice of different MHC types and are able to discriminate between MHC-congenic mice by their urine odors, but nothing is known about behavioral differences among MHC-congenic mice. The present experiments examine the strain and sex differences in MHC-congenic C57BL/6J and B6-H-2K mice with respect to exploration and fear motivated behaviors in the elevated plus maze, the elevated zero maze, and the open field. In the elevated plus maze and elevated zero maze, C57BL/6J mice spent more time in the open areas than B6-H-2K mice, suggesting that they were less fearful and more exploratory. No sex differences for exploration were found but male mice defecated more than females in the elevated plus maze. In the open field there were no significant strain or sex differences in measures of exploration or fear. There were no strain differences in the investigation of a novel object placed into the open field, but males investigated the novel object more than females. These results indicate that there are differences in exploratory and fear behavior in MHC-congenic mice that may contribute to mate preferences and that behavioral differences in these mice might be further examined advantageously.