[avisser]

Perhaps my favorite science experiment, next to dual-slit, https://radiolab.org/podcast/197242-gut-feelings

They cut the vagus nerves of rats and see behavior change.

Which makes sense to me - when "brains" first evolved, the connection to the stomach would've been the prime connection.

[jinder]

Not just that. In mice, SSRIs stop having any anti-depressant effects if the vagus nerve is severed: https://www.nature.com/articles/s41598-019-50807-8

So they also seem to be effective via the enteric nervous system!