Multiple conductance classes of mouse nicotinic acetylcholine receptors expressed in Xenopus oocytes

Acetylcholine receptor (AcChoR) subunit mRNAs transcribed from mouse BC3H-1 cDNAs were injected into Xenopus oocytes and the expressed AcChoR channels were examined by single channel recording. Injection of α-, β-, γ-, and δ-subunit mRNAs produced two predominant channel classes with conductances of ≈50 and ≈12 pS, while infrequent openings of ≈25-pS channels were also observed. Injection of α-, β-, and γ-subunit mRNAs produced a single class of ≈12-pS AcChoR channels, which resembled the smallest conductance channels present in αβγδ-injected oocytes. Assembly of δ-less channels may thus explain the lowest conductance AcChoR channels in αβγδ-injected oocytes and might also account for similar channels that have been observed in vertebrate skeletal muscle.