Recent studies have suggested that psychedelic drugs may be effective in treating PTSD and treatment-resistant depression. To understand how these substances work, researchers have been exploring their molecular-level effects.
In this Ars Technica article, we meet the scientists doing the research.
Serotonin signaling is complicated. There are seven classes of receptors in humans; some activate signaling pathways, while others inhibit them. One group of receptors allows ions into a cell in response to serotonin, triggering nerve impulses. The rest interact with proteins inside the cell, triggering longer-term responses to serotonin. Psychedelics such as LSD and mescaline bind to members of this latter group and activate it.
It appears that psychedelics bind to a specific serotonin receptor, activating it. This is similar to how SSRIs (selective serotonin reuptake inhibitors) work, but psychedelics produce mind-altering effects that SSRIs do not.
Further research has revealed that psychedelics may activate serotonin signaling in a different way than serotonin itself, reaching receptors in parts of the cell that serotonin cannot. Additionally, psychedelics seem to cause changes to nerve cells that allow them to alter their connectivity, potentially allowing them to escape the network configuration associated with a medical disorder.