抄録
The mammary glands of rats which kept intact for 8 days after the removal of the litter on the 7th day of lactation, consisted only of islands of cell clusters which were remnants of ducts. An administration of oxytocin prevented the involutional change slightly which followed weaning. On the other hand, the relatively good preservation of the alveolar system, which seemed to be ascribed to the sucking stimuli, was observed in the rats which had hypothalamic lesions, and failed in rearing. In spite of the well preserved alveolar systems of the mammary gland in the rearing-failed lesioned rats, the values of the R. Q. were lower than unity.
The animals with hypothalamic lesions were subjected to the replacement with oxytocin. The more evident preservation of mammary secretory systems was observed than the rearing-failed lesioned animals without oxytocin replacement. The R. Q. of the mammary glands of the rats replaced with oxytocin remained in a high level.
It seems reasonable to infer that the histological integrity is maintained by prolactin secreted from the anterior pituitary through the suckling stimulus, and in order to maintain a high synthetic activity of the secretory cells, the removal of accumulated products in the alveoli is required in addition to the suckling stimulus.
