http://www.news-medical.net/news/20250804/Psychedelic-and-non-hallucinogenic-drugs-promote-neuroplasticity-through-shared-pathways.aspx :

The prevailing hypothesis in the field was that psychedelics promote neuroplasticity by causing this big burst of glutamate in the brain, which then turns on intermediate early genes. We now know that non-hallucinogenic compounds like TBG can promote neuroplasticity without inducing a glutamate burst or immediate early gene activation."

—David E. Olson, director of the Institute for Psychedelics and Neurotherapeutics and a professor of chemistry and of biochemistry and molecular medicine at UC Davis

Also cf.: http://www.nature.com/articles/s41386-022-01389-z .