Natural hibernation—an animal model for seasonal affective disorder?

1. 1 In Turkish hamster ( Mesocricetus brandti) held under natural light conditions, constant light-dark cycles (LD 10:14), or continuous light, application of lithium chloride in the drinking water at the beginning of the hibernation season (“ treatment) delayed or suppressed daily torpor or hibernation if the daily uptake of LiCl was above 100 μg per g body wt. 2. 2 Application of LiCl from 3 weeks of age (“chronic” treatment) did not affect torpor but reduced mortality to 17% as compared to 42% in acutely treated hamsters. 3. 3 The results indicate a direct effect of lithium on functions interfering with the expression of torpor rather than indirect effects via the circadian system.