Integration of Nervous and Endocrine Signaling (3A) Practice Test

A clinical trial evaluates a new centrally acting $b2$-adrenergic agonist intended to treat attention deficits. Investigators monitor endocrine side effects during a standardized fasting test. Compared with placebo, the drug group shows higher plasma glucagon and higher plasma glucose after 12 hours of fasting, with no difference in measured plasma insulin.

Which outcome would be expected if the drug increases sympathetic-like signaling to pancreatic islets while fasting?

Researchers tested whether acute pain alters prolactin secretion through dopaminergic pathways. Healthy participants underwent a brief noxious heat stimulus. One group received a D2 receptor antagonist beforehand. Serum prolactin was measured at baseline and 20 minutes.

Which of the following best explains the relationship between dopamine signaling and prolactin release suggested by these data?