Serotonin modulates melatonin synthesis as an autocrine neurotransmitter in the pineal gland

Abstract

Significance The pineal gland secretes melatonin at night mainly driven by adrenergic sympathetic inputs. Many other neurotransmitters are found in the pineal gland, suggesting potential fine modulation of melatonin release. Serotonin as a precursor of melatonin synthesis is known to be significantly released by pinealocytes and its receptor also is expressed in pinealocytes. By identifying the release mechanism, cell signaling in the pinealocytes, and its effect on norepinephrine-induced melatonin secretion, our study defines serotonin as an autocrine neurotransmitter in the pineal gland and suggests possible modulatory targets for melatonin secretion.