Recycling of muscarinic M1-M5 receptors. CHO cells stably expressing muscarinic M1 (A), M2 (B), M3 (C), M4 (D) or M5 (E) receptors were incubated with (■) or without (□) carbachol for 1 h. Cells were then washed and treated with cyclized BCM (50 nM) for 5 min as described in section 2.3 “Receptor recycling assay”. Cells were then incubated for various periods of time for up to 90 minutes at 37°C and then used in intact, whole cell [3H]NMS binding assays as described in section 2.5 “Intact, whole cell receptor binding assays”. Each data point represents the mean ± S.E.M. of three to five experiments conducted in triplicate.