The neurohypophysial hormone, oxytocin, is released in response to both external and internal neural stimuli. There is considerable published evidence indicating that release of oxytocin is elicited by the suckling or milking stimulus in the cow (Folley & Knaggs, 1965; Hays & Pritchard, 1967), the goat (Hawker & Roberts, 1957), and the sheep (Fitzpatrick, 1961). There is no published report on the release of oxytocin during suckling in mares, however, and this communication presents the results of the effect of a suckling stimulus on the release of oxytocin in a lactating mare.
The effect of a suckling stimulus was examined in eight mares, all of which were studied less than 1 month after parturition. Foals were isolated from their dams for a period of 5 to 10 hr. A blood sample collected 15 min before initiation of nursing served as a control. Further blood samples were collected at 30 sec,