Pharmacology Which one of the following statements regarding drug effects on serotonin receptor systems is accurate? A 5HT2 receptor blockers counteract bronchoconstriction and diarrhea of carcinoid. B Sumatriptan is an antiemetic because it blocks 5HT3 receptors. C MAO type B inhibitors lead to increased levels of serotonin in the CNS. D Ondansetron is used in migraine because it activates 5HT1D receptors. 💡 Explanation Which one of the following statements regarding drug effects on serotonin receptor systems is accurate? ✓ Correct Answer: A. 5HT2 receptor blockers counteract bronchoconstriction and diarrhea of carcinoid.