Serotonin and melatonin systems (5-HT/MT systems)

The serotonin and melatonin systems represent a complex network of neurotransmitters, enzymes, and receptors that regulate critical physiological processes, including mood, sleep-wake cycles, and circadian rhythms (StatPearls: Physiology, Serotonin, 2023). Serotonin (5-hydroxytryptamine) is synthesized from the amino acid L-tryptophan and serves as the direct biochemical precursor to melatonin (N-acetyl-5-methoxytryptamine) in the pineal gland (StatPearls: Physiology, Melatonin, 2023). These systems utilize a variety of molecular components, including the serotonin transporter (SERT), multiple G protein-coupled receptor families (5-HT1 through 5-HT7, and MT1/MT2), and biosynthetic enzymes like tryptophan hydroxylase and aralkylamine N-acetyltransferase (IUPHAR/BPS Guide to Pharmacology, 2024). Dysregulation of these pathways is central to the pathophysiology of major depressive disorder, anxiety, and insomnia (NCBI: PMC6164985). Pharmacological agents such as selective serotonin reuptake inhibitors (SSRIs) and dual-acting drugs like agomelatine target these systems to treat psychiatric and sleep-related conditions (PubChem: Agomelatine, 2024). Because this entry describes a broad physiological system rather than a single molecular target, it is classified as a system-level pathway in therapeutic contexts.

Other names

5-Hydroxytryptamine and N-acetyl-5-methoxytryptamine systemsSerotonergic and melatonergic pathwaysSerotonin-melatonin axis

Drugs targeting these systems typically act as agonists or antagonists at specific G protein-coupled receptors (e.g., 5-HT1A, MT1, MT2), inhibitors of the serotonin transporter (SERT) to increase synaptic neurotransmitter levels, or modulators of biosynthetic enzymes.