Once a ligand has bound to a receptor, it will continue to generate its response

One way in which ligands will leave their receptor is if the surrounding concentration decreases. This can be achieved by having the ligand leave via the blood where it can be degraded by the liver or kidneys, or by having adjacent cells take up excess ligand. If using the blood, this process will take a little longer. Using adjacent cells is certainly more rapid, but these cells may not always be located in close enough proximity. A third method for reducing local concentrations uses enzymes to digest any free ligand. Again, this is more rapid, but does require the enzymes to be present. Alternatively, the whole receptor-ligand complex can be endocytosed and digested within the cell. It is also possible to inactivate the functional domains of the receptor so that the effects of the ligand are no longer occurring intracellularly.