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.