Neuropeptide K

Where it comes from

Made in

Sensory and brain neurons that make the beta splice form of TAC1

Sent out by

With substance P and neurokinin A

Acts on

• Airway and gut smooth muscle
• Vessels

What it does

• Acts like neurokinin A, more slowly and for longer ¹
• Lowers blood pressure when infused into animals, and raises it when given into the brain
• A tissue form that is cut down to neurokinin A, and cleared from tissue more slowly than the short peptide ³

In medicine

• No medicine copies it or blocks it; the NK2 blockers trialled in asthma and irritable bowel syndrome act at its receptor ¹
• It is not measured in practice. In research it is separated from neurokinin A by chromatography first, since an antiserum to the shared end of the molecule reads both ²

Beyond the body’s own use

• Nothing containing it is in trials, approved or obtainable outside the laboratory
• Its reason for existing is the splice: the beta form of the tachykinin gene puts a 26-residue extension in front of neurokinin A ¹, and the product is slower to act and slower to be destroyed ³
• What is unknown is whether that matters in the body. No animal has been made that can make one splice form and not the other, so nothing shows what a tissue loses when it keeps substance P and loses neuropeptide K ²