pP2 of eserine and neostigmine on acetylcholine responses of isolated ileum.

pP(2) values of 7.9 and 8.0 for eserine and neostigmine show that these compounds are respectively about 200 and 300 times more potent in potentiating acetylcholine (ACh) responses on isolated cavy ileum than was previously found on frog rectus muscle. The increased tone and spontaneity usually produced by eserine and neostigmine were not prevented by morphine (10 to 100 mug/ml), which itself potentiated both ACh and histamine responses.