Effects of hydrocortisone, prolactin and oxytocin on lactational performance of rats

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Abstract
The effects on lactational performance of 0.25-, 0.5- or 1.0-mg doses of hydrocortisone acetate, 1.0 mg prolactin (1.0 mg = 20 iu) or 1.0 iu oxytocin given twice daily, were studied in 90 mature female albino rats of the Carworth strain. Litter weight gains were used as a measure of milk secretion. When hydrocortisone acetate, oxytocin or prolactin were injected individually, only hydrocortisone acetate at the 0.5-mg dose level increased milk secretion significantly (P < .05) and neither prolactin nor oxytocin altered milk yield. When all three hormones were injected in combination, the effects on lactation were the same as with the individual hormones and only the combination containing 0.5 mg hydrocortisone acetate increased milk secretion. These results indicate that adrenal glucocorticoids have the ability to increase milk secretion in the rat and it is believed that this effect is due to its direct action on the mammary gland.