Which of the following best describes how tricyclic antidepressants work upon ingestion?

• A. They inhibit the release of gamma-aminobutyric acid (GABA) in the central nervous system.
• B. They block the reuptake of norepinephrine and serotonin, increasing their levels in the synaptic cleft.
• C. They increase the breakdown of acetylcholine at the synapse.
• D. They directly stimulate dopamine receptors in the brain.

Answer: (B)

Verified step by step guidance

1. Step 1: Understand the role of neurotransmitters in mood regulation, focusing on norepinephrine and serotonin, which are key chemicals involved in depression and its treatment.
2. Step 2: Recognize that tricyclic antidepressants (TCAs) primarily function by affecting the levels of these neurotransmitters in the synaptic cleft, the space between neurons where communication occurs.
3. Step 3: Learn that TCAs block the reuptake (reabsorption) of norepinephrine and serotonin back into the presynaptic neuron, which means these neurotransmitters remain available longer to bind to receptors on the postsynaptic neuron.
4. Step 4: Understand that by increasing the concentration of norepinephrine and serotonin in the synaptic cleft, TCAs enhance neurotransmission and help alleviate symptoms of depression.
5. Step 5: Contrast this mechanism with other options, such as inhibiting GABA release, increasing acetylcholine breakdown, or directly stimulating dopamine receptors, which are not the primary actions of tricyclic antidepressants.