Antibodies to the nicotinic acetylcholine receptor, obtained from serum of myasthenic patients, may decrease...

Release of [3H]-ACh from [3H]-Ch loaded nerve endings from rat hippocampus is dependent on Ca2+ and K+-concentration. [3H]-ACh release, evoked by a depolarizing K+ concentration is decreased in the presence of IgG isolated from the serum of some myasthenic patients but not in that of IgG from controls. Myasthenic IgG contains antibodies to the nicotinic acetylcholine receptor (nAChR). Isolated nerve endings were shown not to be leaky. Curare-sensitive alpha-bgt receptor was found at a concentration of 60-90 fmol/mg protein. It is discussed if a presynaptic nAChR exists in the membrane of hippocampal nerve endings and is involved in an autoregulation of ACh-release or if myasthenic IgG in a manner independent of the receptor.