Program & Abstract Book - EPFL Latsis Symposium 2009

EPFL Latsis Symposium 2009: Understanding Violence
P-48
102
February 11-13 2009
ac u t e s t r e s s h a s a l o n g -l a s t i n g
e f f e c t o n o f f e n s i v e b e h a v i o u r in a
D o m i n a n c e h i e r a r c h y t e s t a n D l e a D s t o a
D o w n r e g u l a t i o n o f m o n o a m i n e o X i D a s e a
e X p r e s s i o n in l a t e r a l s e p t u m
Timmer, Marjan 1 ; Sandi, Carmen 1
1 Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzer-
land
Stress can have a major impact on social behaviour. We use a rat model to
investigate the effect of a stressful experience on the establishment and
maintenance of hierarchies. On day 1, one rat of a pair is exposed to foot
shocks prior to a social encounter and a food competition test (FCT). On
day 8, the memory for the hierarchy established on day 1 is tested in a
water competition test (WCT). Previous experiments in our group showed
that rats that are exposed to a stressful experience before the first encounter
usually become the subordinate individual of a pair. Furthermore,
the memory that is formed for the established hierarchy is enhanced by
stress compared to pairs consisting of two non-stressed rats.
In the present experiment rats were submitted to stress followed by a social
encounter and a FCT on day 1. In a WCT on day 8 they were exposed
to an unfamiliar partner that was either dominant or subordinate on day
1 (without exposure to stress). Stressed rats became the dominant individual
and showed a high ratio of offensive behaviour to a previously subordinate
partner in the WCT, whereas this was not the case when paired
with a previously dominant partner. In addition, we studied changes in
the expression of monoamine oxidase A (MAO A) mRNA expression in the
lateral septum under basal conditions, one week after exposure to stress
and the social encounter. We found a downregulation in MAO A expression
in stressed subordinate rats compared to naïve controls, and in the pairs
consisting of a stressed and a non-stressed rat compared to pairs consisting
of two non-stressed rats.
Our results indicate that exposure to acute stress has a long-lasting effect
on offensive behaviour, which might be explained by the downregulation in
MAO A in lateral septum.