Activation of serotonin 2A receptors (5-HT2ARs) is essential for tryptamine-based psychedelics to produce antidepressant-like effects in rodents. While hallucinogenic properties are generally attributed to 5-HT2AR activation, it was unclear whether these receptors also mediate antidepressant effects, especially because some nonhallucinogenic analogues show antidepressant-like properties. Using pharmacological and genetic tools, the authors demonstrate that 5-HT2AR activation is required for the antidepressant-like effects of tryptamine psychedelics, suggesting that hallucinogenic and therapeutic effects can arise through the same receptor.
Tropane-containing small molecules such as scopolamine can promote neuronal growth (psychoplastogens) but also block all muscarinic receptor subtypes, causing unwanted anticholinergic side effects. Researchers conducted phenotypic structure-activity relationship studies on various tropane subclasses to separate these effects. They identified several novel tropanes that substantially increase cortical neuron growth while showing much weaker activity at all muscarinic receptor subtypes than scopolamine, suggesting that the neuroplasticity-promoting and muscarinic-blocking properties can be decoupled.
Tropane alkaloids and their derivatives are a diverse group of small molecules with many therapeutic uses. Many tropanes affect dopamine and serotonin transporters in the brain. While blocking the dopamine transporter contributes to the addictive potential of tropanes like cocaine, modulating the serotonin transporter may counteract those effects. Serotonin transporter modulators such as MDMA, ibogaine, and SSRIs show promise for treating depression, addiction, and PTSD. This work profiled various tropane subclasses and identified compounds, notably UCD0168 and UCD0820, that potently modulate the serotonin transporter similarly to fluoxetine, MDMA, or noribogaine. UCD0168 acts as a full serotonin releasing agent, and UCD0820 as a partial one. The tropane scaffold can serve as a starting point for developing new serotonin transporter modulators.