Spatial exploration in transgenic mice expressing human beta-S100.

beta-S100 is a calcium-binding protein in the CNS which is involved in the development of the nervous system. In addition, it has been postulated to play a role in long-term potentiation (LTP) in the hippocampus. To test its role in behavior related to hippocampal function, the gene was overexpressed (80 copies) in CD-1 transgenic mice, and the exploration of a novel environment was examined in two experiments. In both experiments subjects' exploratory behavior was observed in an open-field arena containing four objects. No differences in emotional behavior were found between transgenic mice and their controls as measured by the subjects' motility, defecation, and urination. The results of Experiment 1 revealed that transgenic mice explored objects significantly less than the controls, and they did not respond overtly to the spatial change after object displacement. The control CD-1 subjects, on the other hand, showed increased selective reexploration of the displaced object. The results of Experiment 2 replicated the findings of Experiment 1 and revealed more subtle differences in object exploration between the groups. Transgenic mice climbed objects less often and they had longer latencies of object approach than normal CD-1 mice. The study suggests the possible involvement of beta-S100 protein in general exploratory behavior, which includes learning of spatial characteristics of the environment. Specifically, the overexpression of the beta-S100 gene seems to affect the subjects' reactivity to the arousal-inducing properties of novel stimuli.