Every sensory system relies on a neuroepithelial circuit, with a specialized cell at the body’s surface that converts a stimulus into an electrical signal and relays it to the brain. The eye has photoreceptors. The nose has olfactory neurons. The tongue has taste buds. For decades, the gut was thought to lack this kind of direct sensory transduction, communicating with the brain instead through the slow release of hormones into the bloodstream.

That assumption changed with the discovery of neuropod cells, sensory epithelial cells scattered throughout the intestinal lining that form synapses. Through a basal cytoplasmic process, the neuropod, these cells make direct contact with the vagus nerve and release glutamate as a neurotransmitter. The signal reaches the brainstem in milliseconds.

This review surveys what is known about the biology of neuropod cells: how they develop, what they sense, how they synapse, and how that synaptic signal shapes behavior. The implications of gut-brain sensory transduction in understanding appetite, food preference, and the neural basis of visceral instinct are substantial.

https://www.annualreviews.org/content/journals/10.1146/annurev-neuro-091619-022657