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Developmental changes in neural corticosteroid receptor binding capacity in altricial nestlings
Haruka Wada1, Creagh W Breuner
1Section of Integrative Biology, University of Texas at Austin, Austin, Texas 78712, USA. hwada@uwo.ca
Developmental Neurobiology
|July 15, 2010
Summary
Young white-crowned sparrows show a weak adrenocortical response due to immature systems. This study found that changes in mineralocorticoid receptor (MR) binding capacity, not glucocorticoid receptor (GR) binding, may influence this response in developing nestlings.
Area of Science:
- Neuroendocrinology
- Developmental Biology
- Avian Physiology
Background:
- Altricial nestlings exhibit a suppressed adrenocortical response early in development.
- This muted response may stem from an immature hypothalamic-pituitary-adrenal (HPA) axis or heightened negative feedback control.
- Key brain regions like the hypothalamus and hippocampus are crucial for HPA axis regulation via negative feedback.
Purpose of the Study:
- To investigate the ontogenetic changes in glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) binding capacities in white-crowned sparrow nestlings.
- To determine if altered receptor densities in the brain contribute to the dampened adrenocortical response observed in early development.
- To elucidate the role of negative feedback mechanisms in regulating the HPA axis during avian nestling periods.
Main Methods:
- Quantification of GR and MR binding capacities in the brains of white-crowned sparrow nestlings over a 10-day period post-hatch.
- Analysis of age-related changes in receptor binding within specific brain regions, including the cerebellum, hippocampus, and hypothalamus.
- Comparison of receptor binding patterns between different brain areas to identify localized developmental effects.
Main Results:
- Mineralocorticoid receptor (MR) binding capacity significantly decreased with age throughout the nestling period.
- Glucocorticoid receptor (GR) binding capacity showed no significant age-related changes.
- The observed decline in MR levels was primarily attributed to a decrease in the cerebellum, with no significant age-related changes in the hippocampus or hypothalamus.
Conclusions:
- Enhanced negative feedback, mediated by GR and MR in the brain, does not appear to be the primary driver of the attenuated adrenocortical responses in white-crowned sparrow nestlings.
- The developmental trajectory of MR binding, particularly in the cerebellum, may play a role in modulating the HPA axis response during early life stages.
- Further research is needed to fully understand the complex regulatory mechanisms underlying the HPA axis maturation in altricial birds.
