Role of the pineal gland in the photoperiodic control of reproductive and non-reproductive functions in mink (Mustela vison).

摘要: Mink are long-lived mammals that exhibit seasonal changes in body weight, gonadal activity, pelage and plasma prolactin levels. Mating February-March is followed by an obligatory delay implantation during which the corpora lutea stay quiescent. All these events controlled annual variations daylength. The role of pineal gland its product, melatonin, conveying photic information to target organs has been studied. Pineal denervation bilateral ablation cervical superior ganglia rendered mink unresponsive artificial manipulations daily photoperiod: progesterone secretion spring moult were no longer stimulated long days or inhibited short pregnant females; same way increase weight late summer autumn advanced shortening photoperiod. Pinealectomy seemed desynchronize moulting cycles from those intact mink. Melatonin injections reproduced effects on hormonal delayed period. capsules given males phase testicular activity decrease regression onset exactly as did days. In contrast, melatonin administered inactivity triggered recrudescence this short-day breeder. These results support hypothesis all photoperiodic signals conveyed gland. But although seems essential for timing cycles, it does not modify themselves once they initiated.