Artificial induction of lactation in ewes: the involvement of progesterone and prolactin in lactogenesis.

An attempt has been made to evaluate the importance of prolactin and 'progesterone withdrawal' for lactogenesis. The experimental model system used was the ovariectomized, non-pregnant ewe induced to lactate artifically by treatment with trigger hormone (either oestrogen, glucocorticoid or oxytocin) alone or in combination with progesterone. It appears from the results that prolactin is important in the lactogenic responses elicited by oestrogen and oxytocin but not as important in the response elicited by glucocorticoid. Moreover, the results suggest that, in the ewe, an appropriate positive hormonal stimulus will overcome the inhibitory influence of progesterone on lactogenesis.