PACAP-27

Where it comes from

Made in

Hypothalamus, trigeminal and other sensory ganglia, adrenal medulla, gut

Sent out by

With PACAP-38, of which it is a tenth

Acts on

• Neurons
• Vessels
• Adrenal chromaffin cells
• Immune cells

What it does

• Dilates vessels and protects neurons like PACAP-38 ¹
• Two-thirds identical to VIP, the closest relative of the pair ¹
• The minority form in nearly every tissue, about a tenth of what PACAP-38 provides ¹

In medicine

• Covered by the PACAP-38 card. An infusion of PACAP-27 brings on a migraine-like attack in people with migraine, as PACAP-38 does, which showed the headache does not need the longer peptide ²
• It is not measured separately in practice; the assays used in headache research are directed at PACAP-38, the form that makes up most of what tissue holds ¹

Beyond the body’s own use

• Nothing containing PACAP-27 is approved or obtainable outside the laboratory
• The antibody now in development binds the peptide rather than a receptor, so it neutralises both forms; the phase 2 trials that reduced migraine days therefore say nothing about which of the two matters ³
• What is unknown is whether the short form has work of its own. It is two-thirds identical to VIP and a tenth as abundant as PACAP-38, and because the same gene and the same cut produce both, no animal exists that keeps one and loses the other ¹