Perhaps the first link forged in the chain of knowledge concerning the cause of myasthenia gravis was Bernard's research with frogs on the mode of action of curare, which causes paralysis of muscles. Later, it was demonstrated that muscles of myasthenic patients, when stimulated through their nerves, fail to respond, as though they have been poisoned with curare. The concept soon evolved that acetylcholine interacted with receptor molecules on muscle where the nerve terminated. Curare blocked the action of acetyicholine and so decreased its effectiveness. Having a chemical that could tightly bind to the acetylcholine receptor, other investigators used the toxin to obtain large quantities of acetylcholine receptor molecules from the electric eel Torpedo, whose electricity-producing organ contains large quantities of acetylcholine and acetyicholine receptors.
Receptor proteins can also produce antibodies.
Indeed, in an attempt to make such antibodies, scientists injected the acetylcholine receptor protein into rabbits. Unexpectedly, the rabbits developed a complete clinical picture of myasthenia gravis, which led to the recognition that myasthenia gravis is an autoimmune disease. In fact, it is now one of the most completely understood autoimmune diseases. For some reason, the body produces antibodies that specifically bind to and decrease the functional activity of acetylcholine receptors. The search for an understanding of myasthenia gravis in humans has involved frog muscles, rodent neuromuscular synapses, snake toxin, electric eel receptors, and rabbit antibodies.