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Correlations between hypothalamus-pituitary-adrenal axis parameters depend on age and learning capacity
O C Meijer1, B Topic, P J Steenbergen
1Division of Medical Pharmacology, Leiden/Amsterdam Center for Drug Research and Leiden University Medical Center, P.O. Box 9502, 2300 RA Leiden, The Netherlands. o.meijer@lacdr.leidenuniv.nl
Endocrinology
|November 27, 2004
Summary
Aging and learning ability impact the hypothalamus-pituitary-adrenal (HPA) axis. Individual differences in spatial learning reveal age-related HPA axis alterations, suggesting adaptive set-points influence cognitive function.
Area of Science:
- Neuroscience
- Endocrinology
- Behavioral Biology
Background:
- Glucocorticoid hormones, released via the hypothalamus-pituitary-adrenal (HPA) axis, influence brain functions like synaptic plasticity and memory.
- Individual differences in spatial learning and memory exist across ages, allowing for classification into superior and inferior learners.
Purpose of the Study:
- To investigate associations between HPA axis activity measures and cognitive functions in young and aged rats.
- To determine if correlations between HPA axis markers are influenced by age and learning performance.
Main Methods:
- Rats were categorized as superior or inferior spatial learners based on water maze performance.
- Basal and stress-induced HPA axis activity markers (ACTH, corticosterone) and gene expression (CRH, glucocorticoid receptor, mineralocorticoid receptor, AVP) were analyzed.
- Correlations between HPA axis markers were examined in relation to age and learning ability groups.
Main Results:
- Aged rats showed increased basal ACTH, with exaggerated stress-induced ACTH in aged-inferior learners.
- Aged-superior learners exhibited lower hypothalamic glucocorticoid receptor and CRH mRNA expression.
- Correlations between HPA axis markers were significantly dependent on age and learning performance, with unique patterns observed in superior learners.
Conclusions:
- The interdependencies among HPA axis markers vary across distinct age and learning subgroups.
- These variations suggest adjusted HPA axis set-points, potentially reflecting age-independent adaptations influencing learning ability.