Exploring seasonal fluctuations in dopamine D2/D3 receptor availability in healthy adults: A [¹¹C]PHNO imaging study

Dopamine is a neurotransmitter implicated in functions ranging from motor control to cognitive performance. In humans, dopaminergic markers have been associated with seasonal symptomatic fluctuations. Here we investigated potential seasonal variations in dopamine D2/D3 receptor availability in healthy adults using [¹¹C]PHNO positron emission tomography (PET).

Data were retrospectively extracted from a database at the Yale School of Medicine. All healthy participants with non-displaceable binding potential (BP_ND) measurements using [¹¹C]PHNO over the past 20 years were included. Scan dates were used to group participants into spring, summer, fall, and winter groups and daylight hours and average daily temperatures on the scan dates were extracted from appropriate sources. Mixed-effects models were used to investigate the predictive potential of daylight exposure and average daily temperatures for [¹¹C]PHNO BP_ND.

Participants (n = 124, 85 men; mean age = 34.77(9.52) years) demonstrated no significant differences in [¹¹C]PHNO BP_ND levels between those scanned in different seasons. Additionally, mixed-effects analyses revealed no significant associations between daylight exposure and average daily temperatures and [¹¹C]PHNO BP_ND after adjusting for age, sex, and body mass index as fixed effects and subject as a random effect.

Our findings do not provide strong evidence for significant seasonal variations in dopamine D2/D3 receptor availability in healthy individuals. However, variations in PET ligand, geographic latitude, and seasonal daylight exposure may affect findings. These factors should be carefully considered for a fuller understanding of seasonal variation in dopamine receptor imaging studies.