What effect do Selective Serotonin Reuptake Inhibitors (SSRIs) have on serotonin levels?

Selective Serotonin Reuptake Inhibitors, or SSRIs, function by inhibiting the reuptake of serotonin in the synaptic cleft. This means that when serotonin is released into the synapse, it remains in that space longer because the SSRIs block its reabsorption back into the presynaptic neuron. By preventing the reuptake process, SSRIs effectively increase the availability of serotonin to bind with postsynaptic receptors, thereby enhancing serotonergic neurotransmission.

This mechanism is pivotal for the treatment of various mood disorders, such as major depressive disorder and anxiety disorders, as increased serotonin levels can lead to improved mood and reduced anxiety. In contrast to the other options presented, which describe actions that do not align with the pharmacological activity of SSRIs, the correct understanding focuses on the enhancement of serotonin's action at the synapse due to reuptake inhibition.