Fluorescence microscopy images (top row) and corresponding bright-field images (bottom row) of UR-CG072 binding to CHO-K1 cells. Either wild-type CHO-K1 cells (c1 and c2) or CHO-K1-hM4R cells (a1, a2, b1, b2) in DMEM/F12 medium with added 9% FBS and antibiotic antimycotic solution were incubated with 2 nM UR-CG072 in the absence (a1, a2, c1, c2) or presence (b1, b2) of 5 µM scopolamine for 3 h. The number of seeded cells per well was 30 000. The contrast of fluorescence images was enhanced for presentation purposes only, the same lookup table was used for all images. The scale bar corresponds to 50 µm.