March 2, 2023

Sex counts in the brain as seasons change

Photoperiod, or length of day, has sex-specific impacts on dopamine dynamics in the brain, offering insights into sex differences in neuropsychiatric disorders, Vanderbilt researchers report.

Photoperiod, or length of day, influences seasonal changes in disorders such as depression and bipolar disorder, with these changes being more prevalent in females. Not incidentally, there are known sex differences in the brain’s reward pathway, where release of dopamine into the nucleus accumbens (NAc) has been implicated in mood disorders.  

In eNeuro, Alexis Jameson, PhD, Brad Grueter, PhD, and colleagues report the first study of photoperiod effects on the reward system at the synaptic level. 

Performing electrochemical measurements on a subsecond time scale with a method called fast-scan cyclic voltammetry, the researchers found that photoperiod modulates dopamine in the NAc in female mice, but not in males. Release and uptake of dopamine was enhanced in the NAc of female mice raised in long, summer-like photoperiods, spelling a potential neural circuit basis for sex-linked seasonality in affective behaviors. 

The authors note that, beyond its immediate findings, the study introduces an animal model for exploring mechanisms of sex differences in neuropsychiatric disorders.

Others on the study include Justin Siemann, PhD, James Melchior, PhD, Erin Calipari, PhD, and Douglas McMahon, PhD. The study was supported by the National Institutes of Health (MH108562).