Meeting Abstract

P3.149A  Sunday, Jan. 6  Sleeping Dwarfs: Photoperiodic Modulation of Infection-Induced Sleep in Siberian Hamsters (Phodopus sungorus) ASHLEY, N.T.*; ZHANG, N.; WEIL, Z.M.; MAGALANG, U.J.; NELSON, R.J.; Western Kentucky University, Bowling Green, KY; The Ohio State University, Columbus, OH; The Ohio State University, Columbus, OH; The Ohio State University, Columbus, OH; The Ohio State University, Columbus, OH noah.ashley@wku.edu

Infectious challenge or exposure to inflammatory stimuli, such as bacterial lipopolysaccharide (LPS), suppresses wakefulness and rapid-eye movement sleep (REMS) in favor of increased non-rapid eye movement sleep (NREMS). From a functional standpoint, these changes are hypothesized to conserve energy for immune system activation. Many vertebrates exhibit seasonal changes in sleep-wake cycles and immune function, and photoperiod (day length) serves as a reliable environmental cue to anticipate seasonal stressors in the environment. For example, winter is energetically demanding for most animals and Siberian hamsters (Phodopus sungorus) adapted to short winter day lengths display reduced febrile responses after LPS challenge. We hypothesized that short days increase the duration and intensity of NREMS after LPS challenge to create additional energy savings, despite evidence to the contrary that high fever is associated with increased NREMS. Male hamsters were housed under long (16L:8D) or short day lengths (8L:16D), and chronically implanted with transmitters that recorded electroencephalogram (EEG) and electromyogram (EMG) biopotentials simultaneously. After 10 weeks, hamsters received an i.p. injection of LPS or saline (control), and vigilance states (duration and distribution of NREMS, REMS, and wakefulness) and EEG delta power spectra (NREMS intensity) were assessed. Hamsters adapted to short photoperiods displayed cumulatively increased NREMS duration and EEG delta wave amplitude 0-8 h after LPS injection compared to long-day LPS-treated hamsters. These results suggest a seasonal decoupling of LPS-induced fever with sleep to promote energy conservation during predictable energy shortages.