title: Sympathoadrenal system differentially affects photoperiodic changes in humoral immunity of Siberian hamsters (Phodopus sungorus).
abstract: Siberian hamsters (Phodopus sungorus) rely on photoperiod as a primary cue to coordinate seasonally appropriate changes in physiology and behaviour. Among these seasonal changes is reduced immune function in short 'winter-like' days, compared to long 'summer-like' days. Previous evidence suggests that immune function is regulated, in part, by the sympathoadrenal system. The precise role of the sympathoadrenal system in regulating photoperiodic changes in immune function, however, remains unspecified. The goal of the present study was to examine the differential contributions of direct sympathetic innervation of immune target tissue, as well as adrenal medullary catecholamines, to photoperiodic changes in immune function in male Siberian hamsters. In Experiment 1, hamsters underwent either bilateral surgical removal of the adrenal medulla (ADMEDx), or sham surgeries, and were maintained in long (LD 16 : 8) or short days (LD 8 : 16). In Experiment 2, hamsters received either surgical denervation of the spleen, or sham surgeries, and were then housed in long or short days. Serum anti-KLH IgG concentrations and splenic norepinephrine (NE) content were determined in both experiments. Short-day hamsters had reduced humoral immunity compared to long-day hamsters. ADMEDx reduced immune function, but only in long-day hamsters. In contrast, splenic denervation reduced humoral immunity, but only in short-day hamsters. Splenic NE content was increased in short days and by ADMEDx. NE content was markedly reduced in denervated hamsters compared to sham-operated hamsters. Collectively, these results suggest that the sympathoadrenal system is associated with photoperiodic changes in immune function.
authors.affiliation: Department of Biology, Indiana University, Bloomington, IN 47405 USA. gdemas@bio.indiana.edu
authors.forename: G E
authors.initials: GE
authors.lastname: Demas
authors.forename: D L
authors.initials: DL
authors.lastname: Drazen
authors.forename: A M
authors.initials: AM
authors.lastname: Jasnow
authors.forename: T J
authors.initials: TJ
authors.lastname: Bartness
authors.forename: R J
authors.initials: RJ
authors.lastname: Nelson
mesh_terms: D000311:Adrenal Glands / Q000502:physiology*; D000313:Adrenal Medulla / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D000917:Antibody Formation / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D002395:Catecholamines / Q000032:analysis / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D006224:Cricetinae; D004797:Enzyme-Linked Immunosorbent Assay; D007074:Immunoglobulin G / Q000276:immunology; D008297:Male; D009929:Organ Size / Q000502:physiology; D017111:Phodopus / Q000276:immunology*; D017440:Photoperiod; D013154:Spleen / Q000294:innervation / Q000502:physiology; D013564:Sympathetic Nervous System / Q000502:physiology*; D013737:Testis / Q000254:growth & development / Q000502:physiology
chemical_list: D002395:Catecholamines; D007074:Immunoglobulin G