A patient has been diagnosed with depression who responds well to MAO inhibitors. Neurotransmitter which is deficient in this patient is produced from ____
**Core Concept**
The patient with depression responding well to monoamine oxidase (MAO) inhibitors suggests a deficiency in a neurotransmitter that is primarily broken down by MAO. This neurotransmitter plays a key role in mood regulation and its deficiency leads to decreased synaptic levels, contributing to depressive symptoms.
**Why the Correct Answer is Right**
Monoamine oxidase inhibitors (MAOIs) work by irreversibly inhibiting the enzyme monoamine oxidase, which is responsible for the breakdown of certain neurotransmitters. The neurotransmitter that is primarily broken down by MAO and is implicated in depression is norepinephrine, but also serotonin and dopamine. However, the primary neurotransmitter targeted by MAOIs in depression is **norepinephrine**. The deficiency of norepinephrine leads to decreased synaptic levels, contributing to depressive symptoms.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while serotonin and dopamine are also neurotransmitters that are broken down by MAO and are implicated in depression, they are not the primary neurotransmitter targeted by MAOIs.
**Option B:** This option is incorrect because it is not a specific neurotransmitter, and the question is asking for a specific neurotransmitter that is deficient in the patient.
**Option C:** This option is incorrect because it is not a neurotransmitter that is broken down by MAO.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that MAOIs have a "cheese reaction" due to tyramine-containing foods, which can lead to hypertensive crises. Patients on MAOIs should be advised to avoid consuming foods rich in tyramine.
**Correct Answer: D. Norepinephrine**