Do the therapeutic effects of psilocybin involve actions in the gut?

A representative serotonin (5-HT) neuron and synapse. The figure shows predominant cellular locations of 5-HT receptors discussed in the text (5-HT 1 , 5-HT 2 and 5-HT 7 ), with their net effect on cellular activity denoted as excitatory (+) or inhibitory (−). 

https://www.sciencedirect.com/science/article/abs/pii/S0165614723002766

 Approximately 90% of the serotonin the human body produces is in the gastrointestinal tract's enterochromaffin cells, where it regulates intestinal movements.

https://en.wikipedia.org/wiki/Serotonin

A Focus on Enterochromaffin Cells among the Enteroendocrine Cells: Localization, Morphology, and Role

https://www.mdpi.com/1422-0067/23/7/3758

https://en.wikipedia.org/wiki/Enterochromaffin_cell