Review Question - QID 212768

A scientist is studying how animals regulate their blood pressure in response to various stimuli. In particular, she is interested in how much a novel compound that binds to both alpha-1 and beta-1 adrenergic receptors will affect blood pressure. She studies this question in non-human primates, but finds that her results are confounded by the fact that the animals' heart rates start to decrease several minutes after administration of this novel compound. She therefore decides to pretreat these animals with a drug that is known to prevent this decrease in heart rate. Which of the following drugs would most likely achieve the desired effect?