Correction for Liu et al., M₁ Muscarinic Receptors Inhibit L-type Ca²⁺ Current and M-Current by Divergent Signal Transduction Cascades

AA may participate in L-current inhibition by the slow pathway. A, Schematic illustrates putative sites of action for OPC, BSA, and AA. B, Example traces of AA-induced inhibition of long-lasting tail currents. C, Example traces of AA-induced inhibition of long-lasting tail currents in the presence of 10 μM OPC. D, Summary of the effects of 5–10 μM AA in the absence (n = 6) or presence (n = 6) of OPC. AA inhibited both the long-lasting tail current (50 ± 7%; n = 6) and peak current (43 ± 6%; n = 6), similar to its effects in the absence of OPC; *p < 0.05 compared with control current levels when using a two-tailed paired t test. E, Model by which BSA antagonizes M₁R modulation of channels. Control, After its liberation from phospholipids, AA diffuses from the inner to the outer lipid layer of the cell membrane. BSA, BSA binds free AA, facilitating its movement from the outer bilayer into the bath, consequently lowering AA levels in the bilayer and cytoplasm. AA binds to BSA well within several seconds, potentially fast enough to minimize any actions of AA liberated by M₁R stimulation (Kanterman et al., 1990). F, The presence of BSA increased the amounts of AA found in the incubation medium of adult SCG stimulated with Oxo-M for 10 min. ***p < 0.001 compared with no BSA in the bath; n = 5 ganglia per group when using a two-way t test for two means.G, In the presence of 1 μMFPL and 0.5 mg/ml BSA, Oxo-M rapidly and reversibly inhibited peak current, but inhibition of the long-lasting tail current was lost. H, Selected sweeps from G. I, Summary of the effects of BSA (n = 6); p > 0.05 when comparing control (Con) with BSA group.