Background: When rats are subjected to chronic stress for 2 weeks, a significant decrease in hippocampal serotonin (5-HT)1A messenger RNA (mRNA) is observed. We wanted to investigate whether stress, administered for shorter periods of time, would result in decreases in 5-HT1A gene expression in hippocampus.
Methods: In one experiment, rats were either stressed daily for 1 week or implanted with two corticosterone pellets to produce elevated corticosterone levels. In another experiment, rats were subjected to a severe acute stressor and sacrificed 1 day or 1 week after the stressor.
Results: We found that 24 hours after the acute stress, rats showed a significant decrease in 5-HT1A mRNA levels in CA1 and the dentate gyrus compared to controls. No significant changes in 5-HT1A mRNA levels were detected in any of the other groups.
Conclusions: Although 1 week of chronic stress is not sufficient to cause significant decreases in hippocampal 5-HT1A mRNA levels, a severe and prolonged acute stress is capable of down-regulating, at least transiently, 5-HT1A mRNA gene expression in hippocampus.