CC BY
379th multidisciplinary international
Conference of Biological Psychiatry
«Stress and Behavior»
Proceedings of the 9th International Multidisciplinary Conference «Stress and behavior» Saint-Petersburg, Russia, 16-19 May 2005 Editor: Allan V. Kalueff, PhD
CONFERENCE ABSTRACTS
4. EXPERIMENTAL MODELS: M.A. DERYAGINA MEMORIAL SYMPOSIUM
HIPPOCAMPUS-DEPENDENT AND ASSOCIATIVE MEMORY IN MICE SUBJECTED TO ACUTE PREDATOR STRESS
G. Fesenko, E. Shunk, N. Gorenkova, V. Kovalzon Severtsov Institute of Ecology and Evolution, Institute of Reanimathology, Moscow, Russia;
University of Bielefeld, Germany
A number of studies documented contradictory effects of acute stress on learning abilities. Here, we investigated effects of predator stress in mice on two distinct types of memory: a hippocampus-dependent contextual memory and a cortex-dependent conditioned taste aversion associative learning. Also, we related memory scores to individual copying strategies of social behavior. Employed stress paradigm was proposed earlier as a model of extreme environmental stress in humans.
Methods. Male CD1 mice have been tested in a resident-intruder paradigm, in which animals display either dominant or subdominant types of social behavior. Type of social behavior in mice is considered to be a valuable parameter reflecting stress-responsiveness and general style of behavioral coping with various aversive situations. Two month after testing, animals were exposed to predator stress for a time period of 9 h. Therefore they were placed into a small container and introduced to a cage, which was containing a rat; mice were water and food deprived during entire period of stress. Non-stressed animals remained untreated and were kept in regular animal facility. 4 hours after termination of stress, stressed and non-stressed animals were split to two experimental groups and trained in two learning tasks. Half of animals were subjected to a conditioned taste aversion paradigm. Animals were previously trained to a special water drinking schedule, getting a 2-h access to water daily. For training, they received 2.5% sucrose solution and 30 min later were injected with .18 M/kg LiCl that caused nausea in all mice. 24 h later, mice were tested for their preference to sucrose solution (a parameter of associative memory), in a two-bottle paradigm based on a choice between sucrose solution and plain water. Second half of stressed and control animals was trained in a step-down avoidance paradigm. Mice learned to refrain from stepping down onto a grid floor in order to avoid an electric shock. In this test, baseline latency of stepping down, a measure of anxiety-related behavior, as well as short-term and long-term memory was estimated.
Results and discussion. Among control mice subjected to training in conditioned taste aversion paradigm, six out of nine animals showed decreased preference to sucrose (below 50%) as compared to mice not treated with LiCl (mean preference to sucrose 90%) and were considered as good learners. In the stress group, five out of ten animals acquired conditioned taste aversion task. The only difference between the groups was in water drinking: stressed mice showed reduced water consumption. Thus, predator stress does not impair associative learning in conditioned taste aversion paradigm. In a step-down avoidance paradigm, stressed mice showed normal learning scores both for short-term memory (during recall session 3 h after training) and long-term memory (during recall session 24 h after training). However, analysis of good learners from the stress group showed that 80% of them were constituted from mice with subdominant type of behavior. Notably, preliminary experiments in nanve mice did not reveal any differences in acquisition of step-down avoidance between dominant and subdominant groups of mice. In a present experiment, parameters of anxiety were not statistically different between the groups; moreover, dominant mice had a
Psychopharmacol. Biol. Narcol. 2005. Vol. 5, N 2. P. 901-902
Psyhopharmacology & biological narcology
ISSN 1606-8181
tendency to have higher anxiety scores. These data suggest that differences in learning of passive avoidance task between dominant and subdominant mice cannot be explained by unspecific changes in anxiety-related behavior.
Conclusion. Thus, the type of behavioral copying plays a significant role in stress-responsiveness and hippocampus-dependent learning in male mice subjected to acute stress.
Psychopharmacol. Biol. Narcol. 2005. Vol. 5, N 2. P. 901-902
Psyhopharmacology & biological narcology
ISSN 1606-8181
