Review Question - QID 109744

A 49-year-old man presents to his primary care provider complaining of weakness and fatigue. He reports that he has started moving slower than normal and has noticed difficulty buttoning up his pants or tying his tie. He is accompanied by his wife who reports that he has started to move more slowly over the past 2 years. He has also become increasingly irritable and has had trouble sleeping. His past medical history is notable for hypertension, diabetes mellitus, and obesity. He takes enalapril and metformin. His family history is notable for multiple strokes in his mother and father. His temperature is 99°F (37.2°C), blood pressure is 140/90 mmHg, pulse is 90/min, and respirations are 17/min. On exam, strength is 4+/5 bilaterally in his upper extremities and 4/5 in his lower extremities. Some muscle atrophy is noted in his legs and feet. Patellar reflexes are 3+ bilaterally. He has a tremor in his right hand that diminishes when he is instructed to hold a pen in his hand. He is oriented to person, place and time. He states that he feels depressed but denies suicidal ideation. His physician prescribes multiple medications including a drug that is also indicated in the treatment of prolactinomas. Which of the following is the mechanism of action of this medication?