https://www.sciencemag.org/news/2018/09/your-gut-directly-co...
"In a petri dish, enteroendocrine cells reached out to vagal neurons and formed synaptic connections with each other. The cells even gushed out glutamate, a neurotransmitter involved in smell and taste, which the vagal neurons picked up on within 100 milliseconds—faster than an eyeblink."