Our model predicts the existence of personalized synchronization strategies that enable the maintenance of homeostatic rhythms while allowing for differential responses to transient and permanent light schedule changes. By incorporating the interactions across the core, the shell, and the HPA axis, we investigate how these coupled systems synchronize leading to robust circadian oscillations. In this work, we discuss a semi-mechanistic mathematical model that reflects the essential hierarchical structure of the photic signal transduction from the SCN to the HPA axis. The shell converts the VIP rhythmic signals to circadian oscillations of arginine vasopressin (AVP), which eventually act as a neurotransmitter signal entraining the hypothalamic–pituitary–adrenal (HPA) axis, leading to robust circadian secretion of glucocorticoids. The light signal entrains the molecular clock of the photo-sensitive ventrolateral (VL) core of the SCN which in turn entrains the dorsomedial (DM) shell via the neurotransmitter vasoactive intestinal polypeptide (VIP). The suprachiasmatic nucleus (SCN) functions as the central pacemaker aligning physiological and behavioral oscillations to day/night (activity/inactivity) transitions. Effect of daytime oral melatonin administration on neurobehavioral performance in humans. Administration of melatonin when the jet traveler is required to be awake (e.g., for work or driving) should be avoided because melatonin has been reported to impair performance. Adjustment to westward travel should include exposure to dim light/darkness in the morning.
This can be achieved by wearing sunglasses if the sun has not set and by turning the lights down in the house. Adjustment to eastward travel should include exposure to dim light/darkness in the evening. B, Light exposure during the evening and melatonin administration in the morning will induce a westward phase delay shift of the internal circadian clock. A, When entrained to local time, light exposure during the morning and melatonin ingestion in the afternoon will induce an eastward phase advance shift of the internal circadian clock.
Using light and melatonin to phase shift the internal biological time.
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