Veterinary Physiology-III

PINEAL GLAND

• Pineal galnd is also called as epiphysis cerebri.

Location

• Slightly flattened cone-shaped appendage of the brain.
• Its base is slightly constricted to form hollow peduncle by which it is attached to the roof of the third ventricle.

(Picture source: Wikipedia)

• Narrow prolongation of ventricle called pineal recess .
• It contains the highest content of serotonin and the enzyme hydroxyl-indol-o-methyl-transferase (N-methyl transferase) which converts serotonin to melatonin (N-acetyl 5-methoxy tryptamine).

Biological functions

• Lightening of skin colour in amphibia
  • May be also in mammals
• Inhibits gonadal activity in long day breeders
  • Hamsters, Horse
• Stimulates onset of breeding season in short day breeders
  • Sheep
• Long daily periods of elevated melatonin secretion
  • induce ovarian cycles in ewes
• Continuous administration of melatonin induces cyclicity in acyclic ewes
  • Inhibit ovarian cycles in mares
• Removal of pineal / cutting nerve connections to pineal leads to r emoval of seasonality in seasonal breeders