ABSTRACT
Orexins are recently discovered
neuropeptides synthesized by neurons located in the posteriolateral
hypothalamus. There are about 10,000 to 20,000 of these neurons in the
hypothalamus and their axons extend throughout the brain and spinal cord where
their receptors are located. The word Orexin is a Greek word reflecting orexigenic
(appetite stimulating) activity of hormone. There are two types of
Orexin – Orexin-A and Orexin-B – and these are essentially the same as
hypocretine 1 and 2. Orexin in man has been reported similar to those seen in
several other mammals (example, rats, mices, bovine, porcine, etc). Orexin
receptors (Ox1R and Ox2R) atrophies with age, making their efficiency in
coordinating and regulating several systemic activities to be reduce in older
animals. Activities of Orexin include regulation of anterior pituitary gland
secretions; Regulation of feeding and energy balance in animals; and regulation
of wake/sleep states in animals. Mutation in the gene coding preproorexin or
Ox2R gene results in narcolepsy in mice.
In patients with narcoplexy, Orexin neurotransmission was altered and Orexin
level in cerebrospinal fluid was undetectable. Other disorders such as Obesity,
cataplexy etc have also been reported to be associated with Orexin mutation and
reduction in human.
TABLE OF CONTENT:
1.0 INTRODUCTION
2.0 FUNCTIONS OF OREXIN
2.1 Regulation At The Neuroendocrine System
2.2 Regulation Of Feeding And Energy Balance
2.3 Regulation
Of Sleep / Wake States
3.0 MECHANISM
OF REGULATION
4.0 DISORDERS
ASSOCIATED WITH OREXIN DEFFICIENCY
3.1 Narcolepsy
3.2 Cataplaxy
3.3 Obesity
5.0 SUMMARY AND CONCLUSION
REFERENCES