Final answer:
Drugs that inhibit serotonin reuptake cause an increased concentration of serotonin in the synaptic gap, facilitating improved signal transmission, especially in depression treatment.
Step-by-step explanation:
Drugs that block the reuptake of serotonin, a neurotransmitter, increase the concentration of serotonin molecules in the synaptic gap. Selective serotonin reuptake inhibitors (SSRIs) are an example of these drugs that block the transport of serotonin back into the presynaptic neuron, leading to an accumulation of serotonin in the synaptic cleft. This heightened presence of serotonin can enhance its effects at the synapse, often used to treat depression, which is linked with low levels of serotonin.