Final answer:
Selective Serotonin Reuptake Inhibitors (SSRIs) block the reuptake of serotonin into the presynaptic neuron, increasing the levels of serotonin in the synaptic cleft. This helps treat conditions like depression.
Step-by-step explanation:
Selective Serotonin Reuptake Inhibitors (SSRIs) operate at the synapse by blocking the reuptake of serotonin into the presynaptic neuron. This blockage increases the levels of serotonin in the synaptic cleft, allowing it to remain active for longer durations. By strengthening the effect of serotonin, SSRIs can help treat conditions such as depression. Common examples of SSRIs include Prozac, Paxil, and Zoloft.