Conflicting effects of exercise on the establishment of a short-photoperiod phenotype in Syrian hamster.
In the Syrian hamster, winter seasonal inhibition of reproduction occurs in response to decreasing day length. This inhibitory response is modulated by nonphotic cues. In particular, access to a running wheel has been shown to produce incomplete gonadal regression. The present study sought to determine whether this occurs as a consequence of wheel effect on adaptation of the circadian system to short days or whether downstream physiological responses are involved. Short-day adaptation of the circadian clock, which is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, was tested by lengthening the photosensitive phase of the SCN (assayed by light-induced c-Fos expression in the SCN) as a parameter. We found that wheel-running activity does not inhibit the integration of the photoperiodic change by the SCN even if complete testicular regression is prevented. Moreover, this exercise was even capable of accelerating the lengthening of the photosensitive phase after the transfer to short day length. Thus, although wheel-running activity inhibits the short photoperiod-induced gonadal regression, it acts on the SCN to accelerate the integration of the photoperiodic change by the biological clock.
ULP-CNRS UMR 7518, Neurobiologie des Rythmes, IFR Neurosciences 37, 12 rue de l'Université, 67000 Strasbourg, France.
Jerome S
JS
Menet
Patrick
P
Vuillez
Daniel
D
Bonn
Aurore
A
Senser
Paul
P
Pévet
D000222:Adaptation, Physiological; D000273:Adipose Tissue / Q000502:physiology; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D006224:Cricetinae; D004822:Epididymis / Q000502:physiology; D005247:Feeding Behavior / Q000502:physiology; D008297:Male; D008647:Mesocricetus; D009043:Motor Activity / Q000502:physiology*; D009929:Organ Size; D010641:Phenotype; D017440:Photoperiod; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis; D012669:Seminal Vesicles / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000378:metabolism / Q000502:physiology; D013737:Testis / Q000502:physiology
D016760:Proto-Oncogene Proteins c-fos