Figure 3

³H-NMS binding to isolated parotid gland membranes. (A) Typical example of total (•) and nonspecific ³H-NMS binding (◊) (³H-NMS binding in the presence of an excess amount of unlabelled ligand) to membranes from rat parotid glands allow the calculation of specific ³H-NMS binding (○). (B) Inhibition of ³H-NMS binding to rat parotid gland muscarinic receptors by the full muscarinic receptor agonist methacholine in the absence (•) or presence (○) of the stable GTP-analogue GppNHp. Lines are best computer-fit curves according to a two-site (solid line) or a one-site (dotted line) binding model. The two binding sites revealed in the absence of GppNHp are converted into a single site in the presence of GppNHp. Results from one, typical experiment.