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Lateral hypothalamus: early developmental expression and response to hypocretin (orexin)
A N Van Den Pol1, P R Patrylo, P K Ghosh
1Department of Neurosurgery, Yale University Medical School, New Haven, Connecticut 06520, USA.
The Journal of Comparative Neurology
|April 12, 2001
Summary
Hypocretin peptide significantly enhances neuronal activity in the developing rat brain, impacting crucial functions like sleep and feeding from birth. This excitatory influence is vital for early development and survival.
Area of Science:
- Neuroscience
- Developmental Biology
Background:
- Hypocretin (also known as orexin) is a peptide synthesized in the lateral hypothalamic area (LH).
- It is implicated in regulating sleep, arousal, feeding, and endocrine functions, essential for survival.
- The developmental trajectory of the hypocretin system is not well understood.
Purpose of the Study:
- To investigate the developmental profile of the hypocretin system in rats.
- To determine the role of hypocretin in early neuronal development and function.
Main Methods:
- Northern blot analysis for hypocretin and receptor mRNA expression.
- Immunocytochemistry for hypocretin-2 peptide localization.
- Whole-cell patch clamp recordings and calcium imaging in hypothalamic slices and cultured cells.
Main Results:
- Hypocretin mRNA expression increased from postnatal day 1 to adulthood.
- Hypocretin receptor mRNAs were highly expressed early in development, decreasing in maturity.
- Hypocretin-2 peptide was detected as early as embryonic day 19.
- Hypocretin application robustly increased synaptic activity in LH neurons from the day of birth.
Conclusions:
- Hypocretin exerts a potent excitatory influence on developing neurons.
- This early influence may be critical for the maturation of arousal, sleep, feeding, and endocrine systems.
- The findings highlight the importance of the hypocretin system in early life development.