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Orexin expression and function: glucocorticoid manipulation, stress, and feeding studies
Gemma K Ford1, Kamal A Al-Barazanji, Shelagh Wilson
1Henry Wellcome Laboratory for Integrative Neuroscience and Endocrinology, University of Bristol, Dorothy Hodgkin Building, Whitson Street, Bristol BS1 3NY, United Kingdom.
Endocrinology
|June 18, 2005
Summary
Glucocorticoid manipulation affects feeding behavior in rats. Corticosterone replacement reversed adrenalectomy-induced feeding reduction and increased orexin mRNA in the brain, suggesting integrated stress and feeding regulation.
Area of Science:
- Neuroendocrinology
- Behavioral Neuroscience
- Molecular Biology
Background:
- Orexin-A plays a role in feeding behavior.
- Glucocorticoids are key stress hormones influencing various physiological processes.
Purpose of the Study:
- To investigate the impact of glucocorticoid levels on orexin-A-induced feeding.
- To examine the effect of glucocorticoid manipulation on prepro-orexin mRNA expression in the lateral hypothalamic area (LHA).
Main Methods:
- Adrenalectomy (ADX) and corticosterone (CORT) replacement in rats.
- Measurement of orexin-A-induced feeding behavior.
- Quantification of prepro-orexin mRNA levels in the LHA using in situ hybridization.
Main Results:
- ADX reduced orexin-A-induced feeding, an effect reversed by CORT replacement.
- CORT up-regulated prepro-orexin mRNA in the morning but not the evening.
- Partial abolition of orexin-A-induced feeding by ADX suggests dual regulatory pathways.
Conclusions:
- Orexin expression is sensitive to glucocorticoid concentrations, particularly in the morning.
- Endogenous glucocorticoids may not tonically regulate basal orexin expression.
- An integrated relationship exists between orexin, stress, glucocorticoids, and feeding patterns in rats.