Reason for inactivation

Inactivation permits synapses to respond to fast changes in presynaptic neuron firing the frequency. Without it the postsynaptic cell cannot be updated on latest changes in the incoming signals. Additionally, by clearing the transmitter from the synaptic cleft, inactivation limits the receptor desensitization. There are three ways in which the transmitter can be inactivated and they are not mutually exclusive: enzyme-catalyzed degradation, bring out of the synaptic cleft back into neurons or glia, or by the passive diffusion away from synapse.