The following is the action of melatonin

The following is the action of melatonin?
a) Facilitates ACTH secretion
b) Prevents sleep induction
c) Regulates the circadian day night rhythm
d) Release of TSH
Correct Answer - C
Ans. C. Regulates the circadian day night rhythm
The principal secretory product of the pineal gland is melatonin.
Melatonin secretion shows a circadian rhythm, the level being higher
at night and lower at day.
This diurnal variation is brought about by norepinephrine secreted by
postganglionic sympathetic nerves that innervate the pineal gland.
In the dark norepinephrine, secretion is increased which acts on β-
receptors to increase intracellular cAMP and cAMP, in turn,
produces a marked increase in N-Acetyl transferase activity, an
enzyme involved in melatonin synthesis from serotonin.