The normal processes of 5-HT and noradrenaline neurotransmission
When a nerve impulse arrives at a 5-HT or noradrenaline nerve terminal the neurotransmitter is released from the synaptic vesicle into the synaptic cleft. Neurotransmitter molecules bind to their specific receptors on the post-synaptic membrane and the nerve impulse is propagated or inhibited, depending on the receptor type. 5-HT and noradrenaline molecules are then released from their receptors and taken back into the nerve terminal via either the 5-HT or noradrenaline re-uptake transporters. 5-HT and noradrenaline are degraded by MAO and COMT, these enzymes are found in both the synaptic cleft and in the nerve terminal.
Click the image to view high resolution version
References
Other peripheral mediators: 5-hydroxytryptamine and purines. In: Pharmacology, 4th edition. Rang HP, Dale MM and Ritter JM. Edinburgh, UK: Harcourt Publishers Ltd, 2001:165–176.
Noradrenergic transmission. In: Pharmacology, 4th edition. Rang HP, Dale MM and Ritter JM. Edinburgh, UK: Harcourt Publishers Ltd, 2001:139–163.