Bioassay of oxytocin on the superfused mammary gland of the mouse, using an automatic apparatus.

1 A sensitive method of assaying oxytocin using the superfused mouse mammary gland is described. The method is shown to be reliable, accurate and precise. Assays are performed automatically and the preparation is stable for at least 18 hours.2 The preparation is relatively insensitive to bradykinin, histamine, 5-hydroxytryptamine, angiotensin, prostaglandin F(2alpha), adrenaline and noradrenaline. The contractions produced by acetylcholine can be abolished by atropine without the sensitivity to oxytocin being affected.3 Vasopressin has a variable activity on the preparation; its potency can be as high as one-fifth that of oxytocin.4 It is concluded that this method compares favourably with other published methods.