Release of oxytocin in unanaesthetized lactating rats.

The action of certain substances on the release of oxytocin has been studied in unanaesthetized lactating rats. The release of oxytocin has been assessed by the increase in weight after suckling of rats separated overnight from the mother. A large variety of substances appear to block the release of oxytocin. These include pentolinium, atropine and chlorpromazine. Adrenaline and noradrenaline also cause a block in the release of oxytocin, and it is suggested that adrenaline blocks the central release of oxytocin as well as blocking its peripheral action. Reserpine and oestradiol in the doses administered did not block the release of oxytocin. Block also occurred after the ingestion of water, ethanol and normal saline, an effect which may be produced indirectly by impulses from the gastro-intestinal tract.