Pharmacology General 5bdcfd2c All 5–HT receptors are heptahelical serpentine receptors EXCEPT : A 5–HT1 B 5–HT2 C 5–HT3 D 5–HT4 High-Yield Explanation All serotonin receptors are G-protein coupled receptors except 5-HT3, which is an anisotropic receptor.