What is a psychedelic drug, and how does it act on serotonin receptors in the brain?
A mushroom, a cactus and a lab-made molecule can all unlock the same tiny docking point on nerve cells, and nobody fully knows why that changes how the world looks.
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Which one is it?
A psychedelic is a drug whose main effect is to push the mind into a non-ordinary state, often called a "trip", with a perceived expansion of consciousness. The classic examples are mescaline, LSD, psilocybin and DMT. Despite looking quite different as molecules, they share one trick in the brain: they bind to and switch on a docking point called the serotonin 5-HT2A .
A is a protein on the surface of a cell that a particular molecule can fit into, passing a signal inside. The 5-HT2A receptor normally answers to serotonin, one of the brain's own chemical messengers. A psychedelic is an imposter that fits the same lock. Because that receptor sits in circuits involved with sensory perception and thinking, switching it on changes how those circuits behave, which fits effects that are mainly about perceiving and thinking.
Step 1: A psychedelic molecule
LSD, psilocybin, mescaline or DMT
Step 2: Fits the 5-HT2A
A docking point on nerve cells
Step 3: switches on
Circuits for perception and thinking change
Step 4: Experience changes
How exactly is still unknown
How do researchers know the is the key? The stronger a drug binds to 5-HT2A, the stronger its effect in humans, and giving a drug that blocks the receptor, such as ketanserin, can abolish the effects. Still, how switching on this one receptor leads to the changes in perception and is not known. That gap is one reason scientists are cautious about big claims for these drugs.
The story has a human thread. Serotonin was found in the brain only in 1953, by Betty Twarog and Irvine Page, and researchers quickly noticed that LSD looks like serotonin in its structure. Yet people did not wait for chemistry: Indigenous peoples have used psychedelic plants and fungi for thousands of years.
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Recap
Classic psychedelics work by switching on the serotonin 5-HT2A receptor, but exactly how that changes perception is still unknown.
๐ก A trick to remember it ยท Many keys, one lock: whatever the molecule looks like, 5-HT2A is the keyhole it turns.
Surprising fact ยท Serotonin was found in the brain in 1953, long after people had used psychedelic plants for thousands of years.
Sources (2)
No source, no claim. Every fact in this lesson (13 claims) cites at least one of these.