Exogenous Oxytocin and Lactation in the Mouse

Abstract

Twenty-four primiparous mice were divided into four equal groups. The four groups were randomly assigned to injections of .5, .25, and .125 IU of synthetic oxytocin or oxytocin solvent. Average daily body weights of mothers and pups were compared over 15 days postpartum. Mammary glands were removed and processed for histological examination. Average body weight gains of mothers were not significantly different among treatment groups. In general, there was no difference in average body weight gain of pups among treatment groups except that in the group nursing mothers injected with .5 IU oxytocin, average weights decreased slowly until by 12 days of age their weight gain adjusted for 4-day weights was less than the .25 and .125 oxytocin groups (P < .10). Microscopic examination of mammary glands revealed that involution occurred in 4 of 6 mice injected with .5 IU oxytocin. Also, the histological appearance of the .25 IU group suggested that this amount of oxytocin enhanced secretory activity of the cells. Milk production response to exogenous oxytocin injection is dependent both on amount of oxytocin administered and on duration and intensity of the suckling stimulus applied. © 1971, American Dairy Science Association. All rights reserved.