The use of the guinea-pig ileum preparation for testing the activity of substances which imitate or antagonize the actions of 5-hydroxytryptamine and tryptamine.

On the guinea-pig ileum, 5-hydroxytryptamine appeared to act in the same way as tryptamine on two types of receptor (morphine-sensitive and phenoxybenzamine(Dibenzyline)-sensitive). The actions of analogues of 5-hydroxytryptamine on the phenoxybenzamine-sensitive receptors resembled their actions on the rat uterus, and the actions on the morphine-sensitive receptors slightly resembled those on the rat fundus strip. The guinea-pig ileum preparation, however, did not appear to be more suitable than the rat uterus and rat fundus strip for testing the ability of compounds to imitate or antagonize 5-hydroxytryptamine.