Neurotransmitters can produce either a fast or a slow response.
•Fast response involves ionotropic receptors where the neurotransmitter binds to a channel-linked receptor.
–All channel-linked receptors are ligand-gated channels.
–The channel opens, the ions flow down their electrochemical gradients, and produce a brief change in membrane potential called a postsynaptic potential (PSP).
•Slow responses act by triggering biochemical changes through G protein-linked receptors.
–These are called metabotropic receptors.
–Activation of the G protein may either open or close an ion channel.
–If the result is a depolarization the response is excitation; if the result is hyperpolarization the effect is inhibition.