Assertion: melatonin | /r/HasProperty | neurotransmitter
Facets:
Source sentences:
text: Melatonin is a neurotransmitter secreted by the pineal gland in the brain at the onset of darkness, initiating the sleep cycle.
text: Melatonin is a neurotransmitter produced by a gland in the brain that regulates the wake/sleep cycle and other daily biorhythms.