Seasonal photoperiod cycling reduces inter-individual variability in mu-opioid receptor density in rats
Rationale: The mu-opioid receptor (MOR) is widely expressed across tissues and plays crucial roles in pain and stress responses, social behaviour, and immune regulation. Recent evidence indicates seasonal variation in in vivo MOR signalling; for example, short photoperiods are associated with reduced central MOR availability, increased MOR expression in brown adipose tissue (BAT), and…
Seasonal changes in the length of day and night have been shown to affect the density of mu-opioid receptors (MOR) in both brain and peripheral tissues in rats. Researchers investigated how this seasonal variation impacts MOR signalling by comparing rats housed under constant photoperiods with those exposed to seasonal photoperiod cycling.
By using ex vivo radioligand binding to directly measure MOR density, the study found that rats experiencing seasonal light fluctuations exhibited markedly reduced variability in MOR density across central and peripheral tissues, including the cerebellum, striatum, and adrenal glands. This stabilization of MOR dynamics at the population level suggests that stress-related adaptations triggered by seasonal changes may synchronize MOR signalling.
The findings highlight the role of seasonal light variation in modulating endogenous MOR signaling and provide insight into its potential influence on mood-related processes.
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