Seasonal variation in brain mu-opioid receptor availability

Lihua Sun; Jing Ping Tang; Heidi Liljenbäck; Aake Honkaniemi; Jenni Virta; Janne Isojärvi; Tomi Karjalainen; Tatu Kantonen; Pirjo Nuutila; Jarmo A. Hietala; Valtteri Kaasinen; Kari K. Kalliokoski; Jussi Hirvonen; Harry Scheinin; Semi Helin; Kim Eerola; Eriika Savontaus; Emrah Yatkin; Juha O. Rinne; Anne Roivainen; Lauri Nummenmaa

doi:10.1523/jneurosci.2380-20.2020

NeuroscienceJournal of NeuroscienceDec 23, 2020

Peer-reviewed journal article

Seasonal variation in brain mu-opioid receptor availability

Lihua Sun iD, Jing Ping Tang iD, Heidi Liljenbäck iD, Aake Honkaniemi, Jenni Virta iD, Janne Isojärvi iD, Tomi Karjalainen iD, Tatu Kantonen iD, Pirjo Nuutila iD, Jarmo A. Hietala iD, Valtteri Kaasinen iD, Kari K. Kalliokoski iD, Jussi Hirvonen iD, Harry Scheinin iD, Semi Helin iD, Kim Eerola iD, Eriika Savontaus iD, Emrah Yatkin iD, Juha O. Rinne iD, Anne Roivainen iD, Lauri Nummenmaa iD

Abstract

Seasonal rhythms influence mood and sociability. The brain -opioid receptor (MOR) system modulates a multitude of seasonally varying socioemotional functions, but its seasonal variation remains elusive with no previously reported in vivo evidence. Here, we studied the seasonal effects on brain MOR availability via analysing a dataset (n=204) of [11C]carfentanil positron emission tomography (PET) scans of healthy volunteers. We found that seasonally varying daylength had an inverted U-shaped functional relationship with brain MOR availability. Brain regions sensitive to daylength spanned the socio-emotional brain circuits, where MOR availability formed a spring-like peak. Causal effect of daylength on brain MOR availability was further verified by a post hoc experiment with repeated PET imaging of rats (n=9) under seasonal photoperiodic simulation. Therefore, the in vivo brain MOR availability in normal humans shows significant seasonal variation, which aligns with expected seasonal variation in mood and suicidality.

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