<P> Melatonin , also known as N - acetyl - 5 - methoxy tryptamine , is a hormone that is produced by the pineal gland in animals and regulates sleep and wakefulness . Melatonin is also produced in plants where it functions as a first line of defense against oxidative stress . </P>
the part of the brain that regulates the production of the hormone melatonin is called
the pineal gland