It's an endogenous peptide made up of 5 amino acids: Glutamine-Arginine-Phenylalanine-Serine-Arginine.
I'm somewhat confused as to how this compound works. It's administered to the rats IV and produces analgesia comparable to morphine.
The article says that "Opiorphin is the human functional homologue of the rat sialorphin, previously identified by a postgenomic approach as an inhibitor of pain perception that acts by potentiating mu- and delta- opiate receptor-dependent pathways".
So is the mechanism of analgesia simply potentiating endogenous opiate peptides, and not opiate receptor agonism?
--------------------------------
Abstract:
Wisner, A., et al. 2006. Proc Natl Acad Sci U S A. 13 Nov 06 [Epub ahead of print]. doi:10.1073/pnas.0605865103
Mammalian zinc ectopeptidases play important roles in turning off neural and hormonal peptide signals at the cell surface, notably those processing sensory information. We report here the discovery of a previously uncharacterized physiological inhibitor of enkephalin-inactivating zinc ectopeptidases in humans, which we have named Opiorphin. It is a QRFSR peptide that inhibits two enkephalin-catabolizing ectoenzymes, human neutral ecto-endopeptidase, hNEP (EC 3.4.24.11), and human ecto-aminopeptidase, hAP-N (EC 3.4.11.2). Opiorphin displays potent analgesic activity in chemical and mechanical pain models by activating endogenous opioid-dependent transmission. Its function is closely related to the rat sialorphin peptide, which is an inhibitor of pain perception and acts by potentiating endogenous micro- and delta-opioid receptor-dependent enkephalinergic pathways. Here we demonstrate the functional specificity in vivo of human Opiorphin. The pain-suppressive potency of Opiorphin is as effective as morphine in the behavioral rat model of acute mechanical pain, the pin-pain test. Thus, our discovery of Opiorphin is extremely exciting from a physiological point of view in the context of endogenous opioidergic pathways, notably in modulating mood-related states and pain sensation. Furthermore, because of its in vivo properties, Opiorphin may have therapeutic implications.