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Effects of chronic corticosterone ingestion on spatial memory performance and hippocampal serotonergic function
V N Luine1, R L Spencer, B S McEwen
1Department of Psychology, Hunter College, New York, NY 10021.
Brain Research
|July 9, 1993
Summary
Chronic corticosterone exposure altered hippocampal serotonin levels long-term. While most rats showed no spatial memory changes, some high-dose consumers experienced impairment, suggesting a potential threshold effect.
Area of Science:
- Neuroscience
- Endocrinology
- Behavioral Science
Background:
- Glucocorticoids, like corticosterone, are crucial for stress response and memory.
- Chronic elevation of glucocorticoids can negatively impact cognitive function and brain neurochemistry.
Purpose of the Study:
- To investigate the long-term effects of chronic corticosterone ingestion on spatial memory and brain monoamine levels.
- To identify specific brain regions and neurotransmitter systems affected by prolonged corticosterone exposure.
Main Methods:
- Rats received chronic corticosterone (400 µg/ml) in drinking water for 8 weeks.
- Spatial memory was assessed using an 8-arm radial arm maze.
- Monoamine levels (serotonin and norepinephrine) were measured in specific brain regions post-treatment.
Main Results:
- Long-lasting increases in hippocampal 5-HT (44%) and decreases in frontal cortex 5-HT (50%) and NE (36%) were observed 5 weeks post-treatment.
- No significant effects on spatial memory performance were found in most treated rats.
- A subset of rats with the highest corticosterone intake exhibited impaired spatial memory.
Conclusions:
- Hippocampal serotonergic terminals are sensitive to long-term corticosterone exposure, potentially serving as an early indicator of glucocorticoid-induced hippocampal dysfunction.
- Behavioral impairments may be related to high-dose exposure, suggesting a possible threshold effect or dose-response relationship requiring further investigation.