Desensitised State

A condition in which a receptor is unresponsive despite the presence of agonist also referred to as a refractory state . Typically this state is the consequence of prolonged exposure to agonist, and occurs after receptor activation it is a built in mechanism to limit a receptor s effects. Mechanistically the desensitised state differs from the resting, closed state of a receptor because in the latter state, a receptor can respond to agonist. This difference predicts that these states are structurally distinct. The desensitised state may also be stabilised by very low concentrations of agonist, such that no measurable activation of the receptor precedes it. Desensitisation is an intrinsic property of many receptors but can also be influenced by other interactions or modifications, such as phosphorylation. 

Agonists activate nAChR by binding to the agonistbinding site (Fig. 1). They can remain bound (often with higher affinity) when the nAChR enters the desensitised state. 

Descending Inhibitory Pathway Desensitised State Desensitization Desmoplakin... 

Besides the given mechanism the stationary concentration of the excited photophysical intermediate is influenced in contact with a partner B. Energy transfer to an acceptor molecule B opens a new reaction channel, but does not form a new reaction product itself. Looking at the photoisomerisation, this energy transfer will reduce the concentration of the excited state. By this step the photoreaction is desensitised or quenched. This quenching can either happen in the singlet state A or at the triplet state A". Both mechanisms are discussed in the following examples. 

---