The psychoplastogen tabernanthalog induces neuroplasticity without proximate immediate early gene activation

Nonhallucinogenic psychoplastogens, such as tabernanthalog (TBG), are being developed as potentially safer, more scalable alternatives to psychedelics for promoting neuronal growth and treating various brain conditions. Currently, it is unclear whether 5-hydroxytryptamine 2A (5-HT2A) receptors and immediate early gene (IEG) activation have a role in the neuroplasticity-promoting effects of nonhallucinogenic psychoplastogens. Here, we use pharmacological and genetic tools in rodents to show that nonhallucinogenic psychoplastogens promote cortical neuroplasticity through the same biochemical pathway—involving 5-HT2A, TrkB, mTOR and AMPA receptor activation—as classic psychedelics and that TBG-induced cortical spinogenesis is required for the sustained antidepressant-like behavioral effect of TBG. In contrast to psychedelics, TBG does not induce an immediate glutamate burst or IEG activation. As these effects have been assumed to be necessary for psychedelic-induced neuroplasticity, our results shed light on the mechanisms by which certain psychoplastogens can promote cortical neuroplasticity in the absence of hallucinogenic effects. Aarrestad et al. show that, in contrast to psychedelics, the nonhallucinogenic psychoplastogen tabernanthalog promotes neuroplasticity through 5-HT2AR activation without immediately increasing extracellular glutamate levels or immediate early gene expression.