Substance P is a member of a group of polypeptides known as neurokinins or tachykinins. It is thought to be the primary neurotransmitter for the transfer of sensory information from the periphery to the spinal cord and brain. Substance P as well as neurokinin NK₁ receptors have been detected in vagal afferent neurons in the area postrema, nucleus tractus solitarius and dorsal motor nucleus of the vagus. Substance P has been shown to increase the firing rate of neurons in the area postrema and nucleus tractus solitarius and to produce retching when applied directly to these areas in animal studies.

 Nociception

 Tachykinins