Tachykinins, such as substance P, are implicated in pain modulation and inflammation.

“So these are brain chemicals. They're different from dopamine and serotonin in that they're not small organic molecules. They're actually short pieces of protein that are directly encoded by genes that are active in specific neurons and not in others. And when those neurons are active, those neuropeptides are released together with classical transmitters like glutamate. Whatever tackyins have been famously implicated in pain, particularly tachikin 1, which is called substance P, one of the original pain modulating. This is something that promotes inflammatory pain.”