5-HT2A Receptor - History

History

Serotonin receptors were split into two classes by Gaddum and Picarelli when it was discovered that some of the serotonin-induced changes in the gut could be blocked by morphine, whilst the remainder of the response was inhibited by dibenzyline leading to the naming of M and D receptors respectively. 5-HT_2A is thought to correspond to what was originally described as D subtype of 5-HT receptors by Gaddum and Picarelli. In the pre-molecular-cloning era when radioligand binding and displacement was the only major tool, spiperone and LSD were shown to label two different serotonin receptors, and neither of them displaced morphine, leading to naming of the 5-HT₁, 5-HT₂ and 5-HT₃ receptors, corresponding to high affinity sites from LSD, spiperone and morphine respectively. Later it was shown that the 5-HT₂ was very close to 5-HT_1C and thus were clubbed together, renaming the 5-HT₂ into 5-HT_2A. Thus the 5-HT₂ receptor family is composed of three separate molecular entities: the 5-HT_2A (erstwhile 5-HT₂ or D), the 5-HT_2B (erstwhile 5-HT_2F) and the 5-HT_2C (erstwhile 5-HT_1C) receptors.