Which of the following statements regarding MAO inhibitors and tricyclic antidepressants is true?

A) Both increase the amounts of norepinephrine and serotonin available for synaptic transmission.
B) MAO inhibitors are prescribed less than tricyclics because MAO inhibitors require dietary restrictions.
C) These drugs are effective treatments for about 65% of depressed patients.
D) All of the above statements are true.

All the statements are true. Both MAO inhibitors and tricyclic antidepressants increase the amounts of norepinephrine and serotonin available for synaptic transmission, which is how they exert their antidepressant effects. MAO inhibitors are indeed prescribed less frequently than tricyclics, partly because they can interact with certain foods and other medications, necessitating dietary restrictions. Lastly, these drugs are effective treatments for about 65% of depressed patients, reflecting the general efficacy rate of antidepressants.