But remember, the story we're after is what happens after that , inside the cell. We'll get to that soon. For years we have known that most antidepressants work by increasing the amount of neurotransmitter in the synapse. It turns out that most antidepressants decrease the amount of neurotransmitter being cleared away. This leaves more of it floating around in the synapse, where it can bind to the receptors of the next cell.
Some antidepressants block the enzyme that chews up neurotransmitter.
Most cells re-use a lot of their neurotransmitter. They have a recycling device that pulls the neurotransmitter out of the synapse and prepares it to be released again. So, if we block the recycling device, you would expect to see more neurotransmitter in the synapse. In fact, it's been part of the puzzle. You see, antidepressants usually take at least days and sometimes weeks to become effective, if they work.