and physiological responses depending on many factors, such as the type of inverse agonist, the type of receptor, mutants of receptors, binding affinities and whether the effects are exerted acutely or chronically based on receptor population density. Because of this, they exhibit a spectrum of activity below the Intrinsic activity level. Changes in constitutive activity of receptors affect response levels from ligands like inverse agonists. To illustrate, mechanistic models have been made for how inverse agonists induce their responses on G protein-coupled receptors (GPCRs). Many types of Inverse agonists for GPCRs have been shown to exhibit the following conventionally accepted mechanism. Based on the Extended Ternary complex model, the mechanism contends that inverse agonists switch the receptor from an active state to an inactive state by undergoing conformational changes. Under this model, current thinking is that the GPCRs can exist in a continuum of active and inactive states when no ligand is present. Inverse agonists stabilize the inactive states, thereby suppressing agonist-independent activity. However, the implementation of 'constitutively active mutants' of GPCRs change their intrinsic activity. Thus, the effect an inverse agonist has on a receptor depends on the basal activity of the receptor, assuming the inverse agonist has the same binding affinity (as shown in the figure 2). See also Agonist Receptor antagonist Autoreceptor References External links Inverse Agonists: An Illustrated Tutorial Panesar K, Guzman F. Pharmacology Corner. 2012 Pharmacodynamics Receptor agonists