It has been suggested that in certain circumstances oxytocin may stimulate the release of prolactin in the rat (Benson & Folley, 1956) and goat (Bryant, Greenwood & Linzell, 1968). In order to test this hypothesis in a physiological situation the changes in blood levels of oxytocin and prolactin were determined in a series of samples taken during parturition in the goat, where oxytocin levels are known to be high (Folley & Knaggs, 1965; McNeilly, Martin, Chard & Hart, 1972).
The cannulation and blood sampling technique has been described previously (McNeilly et al. 1972). Jugular blood samples were taken continuously during the whole of labour in six pedigree British Saanen goats and all plasma samples were stored at −20 °C until assay. Oxytocin was