Suprachiasmatic nucleus (SCN) controls various physiological, endocrine and behavioral functions by regulating conversion of serotonin (5-HT) to melatonin (MEL). Aging leads to alterations in the neural and temporal organization of the SCN leading to circadian dysfunction. Age-induced stoichiometric alterations in daily chronomics of various components of 5-HT metabolism were studied by constructing interactomes between parameters. The levels of tryptophan (TRP), 5-hydroxytryptophan (5-HTP), 5-hydroxytryptamine (5-HT), N-acetylserotonin (NAS), N-acetyl 5-methoxytryptamine (MEL), 5-hydroxyindoleacetic acid (5-HIAA), 5-methoxyindole acetic acid (5-MIAA), 5-hydroxytryptophol (5-HTOH), 5-methoxytryptophol (5-MTOH) and N-acetyltryptamine (NAT) were measured at (Zeitgeber time 0, 6, 12 and 18) in male rat SCN of 3, 12 and 24 months age groups. Age-induced decrease was observed in mean levels of NAS, MEL, 5-HIAA, 5-MIAA, 5-MTOH, and NAT and increase was observed in TRP, 5-HTP, 5-HT and 5-HTOH in rat SCN. Daily pulses decreased with aging significantly for TRP, 5-HT, NAS, MEL, 5-HIAA, 5-MIAA and NAT. We report here, the age-induced change in interactions between various 5-HT metabolism components by middle age (12 m) changing further by 24 m. The daily rhythms persisted with aging for NAS, MEL and 5-HTOH. Though, rhythms were abolished for TRP, 5-HTP, 5-HIAA, 5-MIAA, 5-MTOH and NAT differentially at 12 and 24 m. The MEL administration showed restoration in 5-HT ratio with 5-HTP, MEL and 5-HTOH in 24 m and NAS and 5-HIAA in 12 m SCN. Thus, MEL administration effects alterations of age-induced stoichiometry in levels and chronomics of serotonin metabolic network interactomes.
