Poster abstracts

Poster number 82 submitted by Taryn Aubrecht

Dim light at night interferes with the development of the short-day phenotype and impairs cell-mediated immunity in Siberian hamsters (Phodopus sungorus)

Taryn G. Aubrecht (Department of Neuroscience, The Ohio State University Wexner Medical Center, Institute for Behavioral Medicine Research), Zachary M. Weil (Department of Neuroscience, The Ohio State University Wexner Medical Center, Institute for Behavioral Medicine Research), Randy J. Nelson (Department of Neuroscience, The Ohio State University Wexner Medical Center, Institute for Behavioral Medicine Research)

Abstract:
Winter is a challenging time to survive and breed outside of the tropics. Animals monitor day length (photoperiod) to regulate seasonally appropriate adaptations in anticipation of harsh winter conditions. The net result of these photoperiod-mediated adjustments is enhanced immune function and increased survival in the absence of breeding. Thus, the ability to discriminate day length information is critical for survival and reproduction in small animals. However, during the past century, urban and suburban development has rapidly expanded and filled the night sky with light from various sources, obscuring crucial light-dark signals, which alters interpretation of day lengths. Furthermore, reduced space, increased proximity to people, and the presence of light at night may act as stressors for small animals. Whereas acute stressors typically enhance immune responses, chronic exposure to stressors typically impairs immune responses. Therefore, we hypothesized the combination of dim light at night and chronic stress interferes with enhanced cell-mediated immunity observed during short days. Siberian hamsters (Phodopus sungorus) were assigned to short or long days with dark nights or dim (5 lux) light at night for 10 weeks. Following restraint (6 h/day, 2 wks), delayed type hypersensitivity (DTH) responses were assessed. Both dim light at night and restraint reduced DTH responses. Dim light at night during long nights produced an intermediate short day phenotype including impaired DTH response and partially regressed reproductive organs. These results suggest the constant presence of light at night could negatively affect small species survival by disrupting the timing of breeding and immune responses.

Keywords: dim light at night, cell-mediated immunity, chronic stress