A cholinoceptor antiserum: its pharmacological properties.

1 Sera of rabbits immunized against a nocotinic receptor-rich fraction, obtained from the electric organ of Torpedo marmorata, were tested for their pharmacological activity on different in vitro preparations. 2 Sera containing antibodies against the nicotinic receptor blocked neuromuscular transmission in the phrenic-nerve hemidiaphragm preparation without affecting the muscle responses evoked by direct electrical stimulation. Complement inactivated sera were still active. Immune sera, incubated for 15 min with a receptor-rich fraction, lost their activity. 3 The immune sera antagonized the responses elicited by acetylcholine on the frog rectus abdominis. 4 The immune sera tested in vitro decreased the compound action potential evoked in the superior cervical ganglion of the rat by electrical stimulation of the preganglionic nerve. 5 The sera did not show any activity on muscarinic receptors of the guinea-pig ileum preparation. 6 It is concluded that in sera obtained from immunized rabbits a substance is present with curare-like action, and that this activity is probably due to the presence of antibodies against the nicotinic receptor.