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 postu lated to play a role in longterm potentiation (LTP) in the hippocampus . To test its role in behavior related to hippocampal function, the ge ne was overexpressed (80 copies) in CD-1 transgenic mice, and the expl oration of a novel environment was examined in two experiments. In bot h experiments subjects' exploratory behavior was observed in an open-f ield arena containing four objects. No differences in emotional behavi or were found between transgenic mice and their controls as measured b y the subjects' motility, defecation, and urination. The results of Ex periment 1 revealed that transgenic mice explored objects significantl y less than the controls, and they did not respond overtly to the spat ial change after object displacement. The control CD-1 subjects, on th e other hand, showed increased selective reexploration of the displace d object. The results of Experiment 2 replicated the findings of Exper iment 1 and revealed more subtle differences in object exploration bet ween the groups. Transgenic mice climbed objects less often and they h ad longer latencies of object approach than normal CD-1 mice. The stud y suggests the possible involvement of beta-S100 protein in general ex ploratory 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. (C) 1995 Academic Press, Inc.