Painkiller in saliva

PainkillerA natural analgesic (painkiller) that is six times stronger than the opiate morphine has been found in human saliva.

In 2003, Catherine Rougeot and her colleagues at the Pasteur Institute identified a potent pain sensation inhibitor in rats they called sialorphin. The present work confirms the presence of a related compound in humans. The compound inhibits the same class of proteins as sialorphin.

The analgesic, termed opiorphin (someone not related to the research team registered domain name yesterday!) is a peptide with the amino acid sequence: tyrosine glutamine arginine phenylalanine serine arginine.

In rat studies, injections of opiorphin suppressed pain sensation for both chemical-induced inflammation and acute physical pain. In both cases, the administered dose of 1 mg/kg opiorphin provided the same painkilling power as 3-6 mg/kg of morphine.

The authors hope to next identify which physiological conditions trigger the natural release of opiorphin, but also note that the strong analgesic properties of opiorphin warrants potential exploration for clinical pain management. However, Rougeot cautions that it might not be developable as a conventional painkiller as the compound may also have anti-depressant activity.

I’m curious though, if spit has this potent painkiller why does it hurt so much when you accidentally bite your tongue?

The work is reported in this week’s issue of PNAS.