Upon excitation, synaptic vesicles release neurotransmitter into the synapse where the neurotransmitters are then free to distribute and associate and disassociate with receptors in a concentration dependent basis. Association with post-synapticreceptors results in neurotransmission by activating ion-channels, enzymes, second-messenger systems or protein-synthesis. Association
If norepinephrine is released into the synapse and interacts with a receptor that modulates the neurotransmission of serotonin, the receptor is a:
Extra info: Because the norepinephrine is effecting another type of neuron (serotonin) this is an example of a hetero-receptor.