Pain free and happy from saliva

The title in Proceedings of the National Academy of Science (PNAS, or "penis" in the trade) doesn't sound like much: Human Opiorphin, a natural antinociceptive modulator of opioid-dependent pathways (abstract). The first couple of sentences in the abstract are even less enticing:

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, and human ecto-aminopeptidase, hAP-N (EC

So we turn to New Scientist for a translation: Natural-born painkiller found in human saliva and it turns out to be pretty interesting.

Scientists at the Institut Pasteur in Paris have found a simple molecule in human saliva that prolongs the lifetime of naturally produced human painkillers, the enkephalins. They say it has six times the analgesic potency as morphine without the addictive or psychological side effects. At least according to the rats they tested it on. Rats tend to lie, at least in our experience. That's one of the things that gives them such a bad reputation. That and the fact that they are rats.

Anyway, the new molecule is simple enough that synthesis should be easy, according to the authors. That means we won't have to have gigantic spit distillers. Just chemical factories. But don't get too excited. It hasn't been tested in humans and is suspected of having side effects:

"Its pain-suppressive effect is like that of morphine," says Catherine Rougeot at the Pasteur Institute in Paris, France, who led the research. "But we have to test its side effects as it is not a pure painkiller," she says. "It may also be an anti-depressive molecule."

Anti-depressive side-effects. That's a bummer.


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probably explains thumb sucking.

Rats are actually much more trustworthy than most humans I've met.

deadrose: I thought that comment might raise the hackles of the rat contingent. As a matter of fact, I am a feral rat admirer myself. Mrs. R., on the other hand, feels nuclear weapons are too good for them.

Maybe this is where that kissing bo-bo's came into being?
Oh and rats are cool. At least the pet ones we have. They like spit too. Especially of it has beer or chocolate mixed in with it.

By G in INdiana (not verified) on 15 Nov 2006 #permalink

Hmm, I've got some doubts about this one. There's been a lot of interest in the lay-press as a novel therapy, but I think there are questions remaining.

This being a peptide is presumably going to be no good for oral administration, correct? It'll just get cut to pieces.

If topical rather than oral, say in wounds or ulcers, are the targets (NEP and AP-N) present in open wounds?

If IV rather than either of the above, might there not be a risk of either an auto-immune response or risk of inflammation?

I suspect that this is of more interest to define the targets for small molecule drugs rather than peptide drugs, or am I wrong?

coracle: No, I think you are right on target. This is an interesting article and may lead to a new class of analgesics. But it has a long way to go before anything comes of it, if anything does.

Now I know why my dog licks himself.

I remember reading or hearing many years ago that some component of animal saliva aided in the healing process of open wounds, though I'd never heard of the pain-killing element. They seem to know instinctively that it's good for them; unfortunately many humans find it pretty gross and the idea of "licking one's own wounds" would undoubtedly turn many a stomach. We are, alas, animals ourselves, and I can testify from personal experience that I've often licked a cut or scrape in lieu of antiseptic and can't remember a single one of those injuries becoming infected. Not sure it helped much with the pain, though....

cougar, that is so true - when you punch a hole in your finger it's almost instinctive to stick it in your mouth. Depending on where your finger has been, of course. Our familial custom is to use whisky as antiseptic. This also has fine painkilling qualities.

Dizzy, whiskey as a topical or oral painkiller???

coracle: thanks for the reference, interesting reading, especially the mention about egg whites. I've used them before as a facial toner as they tighten up during drying. Not a pleasant experience but a cheaper and more natural alternative to chemical toners on the market.
Dizzy, hadn't thought about it before but you're absolutely right about instinct kicking in when you get hurt. Looks like science backs it up.

Saliva has other interesting uses. It is used to clean old paintings. A standard conservator's trick is to spit on a tissue and stick on the painting. The painting surface is oxidized linseed oil and enzymes break down various surface-layer reaction and bacterial products.

By Ground Zero Homeboy (not verified) on 23 Nov 2006 #permalink