The release of oxytocin by suckling was demonstrated in unanaesthetized rabbits by recording the uterine motility of the lactating animal by means of a previously inserted intrauterine balloon. The amount of oxytocin released was found to correspond to 1–2 mU intravenously injected oxytocin per each young suckling separately, and to 50–100 mU oxytocin when a whole litter was suckling simultaneously. Ethanol administered either intravenously or orally was found to inhibit this release of oxytocin by suckling. The dose of alcohol necessary for complete inhibition increases with increasing strength of stimulus. Release of 10 mU oxytocin or less could be inhibited by 0.8 g ethanol per kg body weight, whereas 2.0 g/kg body weight was necessary to prevent the secretion of oxytocin by a stimulus, which normally results in the release of about 50–100 mU. Occasionally 3.0 g/kg was needed to inhibit the release of about 100 mU oxytocin.
The release of oxytocin by high doses of acetylcholine injected intravenously into atropinized rabbits was also demonstrated. An oxytocic response corresponding to about 5 mU oxytocin occurred after 10 mg of acetylcholine given intravenously. This release could be inhibited by previous administration of 0.8 g/kg body weight of ethanol.