Lighting conditions alter Candida albicans-induced sleep responses in rabbits

To evaluate the influence of light on sleep patterns after microbial challenge, we studied rabbits housed in 12:12-h light-dark (LD), constant light (LL), or constant darkness (DD) before and after intravenous Candida albicans inoculation. Compared with the LD group, uninoculated LL rabbits sporadically increased slow-wave sleep and delta-wave amplitudes during the circadian period previously associated with the dark phase. In contrast, uninfected DD rabbits showed reduced sleep during the circadian period previously associated with the light phase. Inoculation of LD rabbits with Candida approximately 2 h after light onset increased slow-wave sleep and delta-wave amplitudes during hours 4-8 postinoculation and reduced these parameters during hours 20-46. In contrast, Candida-inoculated LL rabbits demonstrated increased slow-wave sleep for up to 28 h after inoculation, with little subsequent reduction; delta-wave amplitudes were similar to those of LD rabbits. Candida-inoculated DD rabbits demonstrated attenuated increases in slow-wave sleep and delta-wave amplitudes, but the suppression phase was not altered. We conclude that lighting conditions modulate microbially induced sleep alterations.