Exposure to juvenile stress exacerbates the behavioural consequences of exposure to stress in the adult rat
To examine the effects of exposure to post-weaning pre-puberty (juvenile) stress on the emotional and cognitive abilities in response to exposure to stress in adulthood, we first exposed rats to a platform stress at the age of 28 d. Two months later the rats were exposed to acute swim stress. Rats exposed to both stressors showed a higher level of anxiety (as measured both in open-field and startle response tests) than controls or rats exposed to either the juvenile or the adulthood stressor. In the Morris water-maze, rats that were exposed to both juvenile and adulthood stress performed better than the other groups. In a second experiment we verified that the effect of the juvenile stress was indeed age-dependent. One group was exposed at the age of 26–28 d and again at the age of 60 d (juvenile+adulthood stress); the other group was exposed to the first stressor at the age of 60–62 d and to the second at the age of 90 d [adulthood (60)+adulthood (90) stress]. Juvenile+adulthood stress had a significantly greater effect than exposure to stress twice in adulthood, on anxiety level and on the performance in the water-maze. Finally, in a third experiment we found that the juvenile+adulthood stress group swam faster and tended to explore the central area more than the other groups – a finding that could explain their better performance on the first trial of the spatial task. These results indicate that an exposure to a relatively brief juvenile stressful experience has profound and long-lasting effects on the ability to cope with stress in adulthood.(Received February 10 2004)
(Reviewed July 7 2004)
(Revised July 28 2004)
(Accepted August 1 2004)
Key Words: Anxiety; juvenile; PTSD; rat; spatial learning.
c1 Department of Psychology and The Brain & Behavior Research Center, University of Haifa, Mount Carmel, 31905 Haifa, Israel. Tel.: +972-4-824-0962 Fax: +972-4-8288578 E-mail: email@example.com