Post and presynaptic receptors

Post and presynaptic receptors

Some people think of receptors as only sitting on a cell of a target tissue (for example on the post-synaptic neuron of a synapse). But it is important to realize that the target cell can also be found pre-synaptically, helping to regulate the output of a cell. These are sometimes called

autoreceptors.

A good example that shows how the same agonist (adrenaline) can act both pre- and postsynaptically is shown below. The α2 receptor is a Gi coupled protein receptor, thus inhibitory. The β2 receptor (as well as the β1) is stimulatory (Gs-protein).