by Matthew S. Koval, M.D. 

But ... um ... just how do antidepressants really work?

The simple answer is, well, we don’t know for sure. In fact, scientists actually discovered antidepressants by accident.

But before we can move on to that interesting story, we must have a basic understanding of brain neurochemistry. Perhaps in the process we can discover a few clues ...

BRAIN CHEMISTRY
In the human brain, it is vital that nerve cells, or neurons, have the ability to communicate with each other. They achieve this communication by passing along neurochemical signals.

Start by imagining two neurons very close together. One is called the resynaptic neuron and the other is the postsynaptic neuron. Notice that -synaptic” part. In between these two neurons, you see, is a tiny space called the synapse.

The presynaptic neuron (before the synapse) has a small factory inside making important chemical messengers called neurotransmitters. These messengers are packaged into small bubbles and sent to the neuron’s outer surface. The bubble’s contents are dumped from the presynaptic cell into the synapse.

The messengers then travel across the synapse and connect to receptors on the postsynaptic neuron, thereby finally delivering their message. The new message typically results in electrochemical excitement in the postsynaptic neuron, which triggers various activities in that neuron, including making more neurotransmitters. This process continues in a similar fashion on and on down the line of nerve cells.

If any excess neurotransmitters get out into the synapse, the presynaptic neuron has a neat little reuptake pump, or recycle bin, that it uses to scoop up the excess and transport it back into the presynaptic neuron. That way, the leftovers can be sent to the neuron’s incinerator, where they can be destroyed and converted back into raw  materials for the neuron to use in other endeavors.

This is the way most nerve cells work in your brain and body.