Transitional photoperiod induces a mania‐like behavior in male mice

Abstract

This study aimed to investigate the behavioral responses and circadianrhythms of mice to both rapid and gradual increases in photoperiod, mimickingthe transition from winter to summer, which is associated with a heightenedprevalence of hospitalizations for mania and suicidal behavior.Behavioral tests were performed in C57BL/6 male mice exposed to a transitionalphotoperiod, from short to long durations. To determine if circadianrhythms are affected, we measured spontaneous locomotor activity and bodytemperature. Mice exhibited heightened exploratory and risk-taking behaviorscompared with equatorial and static long (16:8 h of light–dark cycle for severaldays) groups. These behaviors were prevented by lithium. Spontaneous locomotoractivity and body temperature rhythms persisted and were effectivelysynchronized; however, the relative amplitude of activity and interdaily stabilitywere diminished. Additionally, the animals displayed increased activityduring the light phase. Photoperiodic transition modulates behavior and circadianrhythms, mirroring certain features observed in bipolar disorder patients.This study introduces an animal model for investigating mania-like behaviorinduced by photoperiodic changes, offering potential insights for suicide preventionstrategies and the management of mood disorders.