At the cellular level, SSRIs target the presynaptic neurons in the brain. Specifically, they bind to the serotonin transporter (SERT) proteins located on the presynaptic membrane. By inhibiting these transporters, SSRIs prevent the reuptake of serotonin into the presynaptic neuron, leading to an increased concentration of serotonin in the synaptic cleft, which enhances serotonergic neurotransmission.
