Which one of the following statements regarding drug effects on serotonin receptor systems is accurate?

Cyproheptadine and ketanserin are 5HT2 receptor blockers used in the management of carcinoid and related states; cyproheptadine also has H1 receptor blocking effects. Sumatriptan is used in migraine (not for emesis) and exerts its effects on cerebral vasculature via activation of 5HT1D receptors. Ondansetron is the antiemetic, a blocker of 5HT3 receptors. Because serotonin is metabolized by MAO type A (which also metabolizes NE and tyramine), drugs like selegiline have no effects on 5HT levels in the brain. Newer antipsychotic drugs (e.g., olanzapine) are 5HT2 receptor antagonists, so it does not appear likely that inhibition of 5HT reuptake would have value in psychotic disorders such an action may be exacerbatory.