Melatonin rhythm and other outputs of the master circadian clock in the desert goat (Capra hircus) are entrained by daily cycles of ambient temperature |
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Authors: | Hicham Farsi Driss Harti Mohamed R. Achaâban Mohammed Piro Véronique Raverot Béatrice Bothorel Mohammed Ouassat Etienne Challet Paul Pévet Khalid El Allali |
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Affiliation: | 1. Comparative Anatomy Unit, Department of Biological and Pharmaceutical Veterinary Sciences, Hassan II Agronomy and Veterinary Medicine Institute, Rabat, Morocco;2. Medicine and Surgical Unit of domestic animals, Department of Medicine, Surgery and reproduction, Hassan II Agronomy and Veterinary Medicine Institute, Rabat, Morocco;3. Laboratory of Hormonology, East Center for Biology and Pathology, East Hospital Group, Civil Hospices of Lyon, Lyon, France;4. Institute of Cellular and Integrative Neurosciences, CNRS and University of Strasbourg, Strasbourg, France |
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Abstract: | In desert areas, mammals such as camel and goat are exposed to harsh environmental conditions. The ambient temperature (Ta) cycles have been shown to entrain the circadian clock in the camel. In the present work, we assumed that, in the goat living in a desert biotope, Ta cycles would have the same synchronizing effect on the central clock. Therefore, the effects of Ta cycles on body temperature (Tb), locomotor activity (LA) and melatonin (Mel) rhythms as outputs of the master circadian clock have been studied. The study was performed on bucks kept first under constant conditions of total darkness (DD) and constant Ta, then maintained under DD conditions but exposed to Ta cycles with heat period during subjective day and cold period during subjective night. Finally, the Ta cycles were reversed with highest temperatures during the subjective night and the lowest temperatures during the subjective day. Under constant conditions, the circadian rhythms of Tb and LA were free running with an endogenous period of 25.3 and 25.0 hours, respectively. Ta cycles entrained the rhythms of Tb and LA to a period of exactly 24.0 hours; while when reversed, the Ta cycles led to an inversion of Tb and LA rhythms. Similarly, Ta cycles were also able to entrain Mel rhythm, by adjusting its secretion to the cooling phase before and after Ta cycles inversion. All together, these results show that the Ta cycles entrain the master circadian clock in the goat. |
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Keywords: | ambient temperature body temperature circadian clock entrainment Goat locomotor activity melatonin |
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