title: Change in duration of the nighttime melatonin peak may be a signal driving photoperiodic responses in the Djungarian hamster (Phodopus sungorus).
abstract: A regime of 14 h of light and 10 h of darkness (LD 14:10) induced regression of testes and accessory glands in adult Djungarian hamsters maintained originally in LD 16:8, but recrudescence of these organs in hamsters maintained originally in LD 8:16. Duration of the period of elevated nighttime melatonin levels in LD 14:10 was the same irrespective of whether hamsters had come from LD 16:8 or from LD 8:16. It is suggested that a change in duration of the nighttime melatonin peak and its direction rather than absolute duration of the melatonin peak may be a hormonal signal driving photoperiodic responses in adult Djungarian hamsters.
mesh_terms: D000818:Animals; D006224:Cricetinae; D005260:Female; D005837:Genitalia, Male / Q000033:anatomy & histology; D008027:Light; D008297:Male; D008550:Melatonin / Q000032:analysis* / Q000097:blood; D009929:Organ Size; D010507:Periodicity; D010870:Pineal Gland / Q000032:analysis*; D012756:Sheep / Q000097:blood
chemical_list: D008550:Melatonin