Kinetics of Synaptic Current

Current kinetics takes into account three key components of receptor function. They include an open or activated state, a deactivated state, and a desensitized state. As the ligand binds to the receptor, a conformational change takes place allowing pore formation and ion permeability, defining an activated state. The deactivated state refers to a receptor transitioning from a bound to an unbound agonist state with decreasing ionic permeability as the channel closes. This process occurs as the agonist concentration becomes zero. Finally, a desensitized state refers to a reduced response to an agonist often due to prolonged agonist exposure (i.e., the receptor is in a nonconducting state despite agonist being bound to the receptor). Desensitization can be altered by neurotransmitter clearance from the synaptic cleft via diffusion, degradation, or reuptake through transporters expressed on neuronal or glial cells. Prolonged exposure to neurotransmission may induce desensitization of receptors, while rapid removal of the neurotransmitter from the synaptic cleft may reduce desensitization.