Reversible inhibition of whole-cell TRPM3 currents by muscarinic receptor stimulation. (A) Representative time course of whole-cell currents in a HEK-M3 cell heterologously expressing the M1 mAChR, illustrating the reversible effect of M1 stimulation by 20 µM Oxo-M in the presence of 10 mM BAPTA in the intracellular solution. (B) Representative I-V traces for the experiment in A. (C) Relative amplitude of the current response to the second PregS application, normalized to the mean of the first and third responses, comparing the effect of vehicle or Oxo-M in HEK-M3 cells with or without expression of the M1 mAChR. (D) Same as A, but in the presence of 5 mM EGTA instead of BAPTA in the intracellular solution. (E) Relative amplitude of the current response to PregS in the presence of Oxo-M and after the Oxo-M wash out, normalized to the PregS response before the Oxo-M application, showing the effect of Oxo-M on HEK-M3 cells with or without expressing the M1 mAChR. (F and G) Same as in A and B, except in an Ins1 cell, which endogenously expressed TRPM3 and mAChR. (H) Comparison of the relative current amplitude of the second and third (recovery) response to the initial PregS application, in cells stimulated with Oxo-M or vehicle. P-values in C, E, and H were obtained by unpaired Student’s t tests.