I’ve read that LSD and MDMA are very different in how they increase Serotonin levels in the brain… but how different SSRIs are to the first two? ….neurologically speaking?… and if SSRI’s increase Serotonin Levels why aren’t folks tripping their asses off when they take them?
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They all affect serotonin, but in different ways and with different effects.
It’s a bit more complicated than there just being a level of serotonin in the brain. There are specific neurons that release serotonin. They run in pathways all over the brain and activate different types of serotonin receptors. Depending on which receptors are activated, when and how strongly, the effects are different.
LSD is the simplest. It directly activates a specific serotonin receptor, the 5HT2A receptor (note that 5HT is another name for serotonin). It’s different from naturally produced serotonin because it’s pretty specific to this receptor, whereas serotonin activates so many other ones as well.
MDMA and SSRIs both affect the serotonin transporter instead of the receptors. The serotonin transporter is the body’s way of getting rid of serotonin once it’s done it’s job. It takes serotonin and pumps it back into neurons, where it’s prepared to be used again.
MDMA reverses this process. Instead of pumping serotonin into cells, it pumps it out. This basically floods the brain with serotonin temporarily, activating all the serotonin receptors. It’s not as specific as LSD. This also explains why people often feel depressed for a few days after using MDMA. They’ve depleted a lot of their serotonin, and it needs time to replenish itself.
SSRIs are the most complicated, because we still don’t fully understand the mechanism of action. They stop the serotonin transporter from pumping serotonin back into cells, but unlike MDMA they don’t reverse it. It just becomes inactive. This more modestly increases serotonin throughout the brain. How this relieves depression, we still don’t know. The thought is that over time the high levels of serotonin cause the receptors to become less sensitive, which changes how to serotonin releasing neurons behave. This would explain why it takes weeks for them to work, even though they increase serotonin within hours.
Other neurotransmitters are also affected, causing some of the effects. For example, LSD also stimulates dopamine receptors. MDMA causes the release of noradrenaline and dopamine as well, but not as strongly as it affects serotonin.
Basically, the difference comes down to which serotonin receptors are being activated, how strongly, and for how long. Serotonin has many different actions in different parts of the brain, and these drugs change some of its actions but not others.
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