Seasonal variation in brain mu-opioid receptor availability

Sun, L.; Tang, J.; Liljenback, H.; Honkaniem, A.; Virta, J.; Isojarvi, J.; Karjalainen, T.; Kantonen, T.; Nuutila, P.; Hietala, J.; Kaasinen, V.; Kalliokoski, K.; Hirvonen, J.; Scheinin, H.; Helin, S.; Eerola, K.; Savontaus, E.; Yatkin, E.; Rinne, J. O.; Roivainen, A.; Nummenmaa, L.

doi:10.1101/2020.05.20.104349

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bioRxiv · 10.1101/2020.05.20.104349

Seasonal variation in brain mu-opioid receptor availability

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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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Sun, L., Tang, J., Liljenback, H., Honkaniem, A., Virta, J., Isojarvi, J., Karjalainen, T., Kantonen, T., Nuutila, P., Hietala, J., Kaasinen, V., Kalliokoski, K., Hirvonen, J., Scheinin, H., Helin, S., Eerola, K., Savontaus, E., Yatkin, E., Rinne, J. O., Roivainen, A., Nummenmaa, L.. 2020-05-22. Seasonal variation in brain mu-opioid receptor availability. https://doi.org/10.1101/2020.05.20.104349

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