THE PHYSIOLOGICAL ROLE OF OREXIN TO THE HUMAN SYSTEM.

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