Many drugs, and most drugs that are directed at cognitive processes (e.g. anti-depressants, hallucinogenics) target receptors. Receptors are proteins involved in the way cells in the body signal to each other. The following is a review of one particular type of receptor called the 5-HT2A receptor, and it’s role in mediating the effects of LSD.
What is a receptor?
Our body is made up of individual units called cells. There are sorts of different types of cells, like muscle cells or fat cells or neuron cells. Neurons are cells that are very good at transmitting signals, and are involved in receiving signals (like when you see something in your eye), or transmitting signals (like when you tell your hand to move), or when you need to process information (like when you imagine something).
There are two major strategies neurons use to send and receive information. (1) Within a neuron, signals can be sent as electricity, and then when it needs to pass on the information to the next neuron then (2) it releases a chemical out across the small gap between neurons to the next neuron. This gap between the two neurons where they signal to each other is called the synapse. The next neuron then receives the chemical and based on how it interprets it, it might signal itself (in which case it will send an electric current) or possibly turn off, or even just slightly modify the way it signals.
The chemicals that neurons use to send messages to each other are called neurotransmitters. There are many different types of neurotransmitters. Some of the famous neurotransmitters include dopamine and serotonin. Neurotransmitters have their corresponding receptors. So if the first cell (called presynaptic) sends serotonin to the next cell (called postsynaptic) then the second receptor will use a serotonin receptor receive the signal. To a certain extent, the relationship between neurotransmitters and receptors is like a key and lock, so that a receptor can normally only be turned on by one particular neurotransmitter.
A detail which makes this all more complicated is that receptors have subtypes. Subtypes are categorized according to their similarity. So, for example, there is a type of receptor called muscarinic receptors which receive signals from the neurotransmitter acetylcholine. To date, there are have been five subtypes of muscarinic receptors identified (M1 through to M5). All muscarinic receptors respond to their main neurotransmitter – acetylcholine – but they can be found in different parts of the body and also respond in different ways upon receiving a signal. Additionally, drugs can take advantage of receptor subtypes by making sure the drug preferentially activates one particular subtype.
What’s the 5-HT2A receptor?
Serotonin is a major neurotransmitter. Confusingly, serotonin is also known by the name 5-Hydroxytryptamine or 5-HT[1].
[1] 5-Hydroxytryptamine isn’t just a random name chosen by scientists to make themselves sound more important. That phrase – “5-Hydroxytryptamine” – is the chemical name for serotonin, so it describes what serotonin is actually made of. ELABORATE.
