Prolactin Delays Hair Regrowth in Mice

The study explored how prolactin influences hair follicle cycling in female Balb/c mice, discovering that prolactin levels rise before the anagen phase and that prolactin receptor mRNA in the skin increases during early anagen. Pharmacologically lowering prolactin with bromocriptine led to earlier hair regrowth by 3-5 days, while exogenous prolactin administration restored normal hair cycling. Prolactin treatments after anagen onset had no effect on the hair cycle. Skin from prolactin receptor-deficient mice grafted onto normal mice exhibited faster hair cycling, suggesting that prolactin directly affects hair growth cycles through the skin. The study concluded that prolactin directly delays hair growth cycle timing in mice. The grafting experiment involved 20 host mice with two grafts each, and skin was obtained from four prolactin receptor knockout and four wild-type mice.