Pain and Gastrin Releasing Peptide Receptors

Gastrin has traditionally been associated with the stomach, but like intestinal vasoactive peptide now takes its place as a mediator of pain (itch).

Sun and Chem report in the current issue of Nature. 2007 Jul 25 that gastrin releasing peptide receptor (GRPR is found in significant amounts in the dorsal horn of the cord, specifically in Lamina I of the spinal cord, which is pain central. The marginal cells of Layer I have always been a bit mysterious, having the ability to sensitize very large areas of the body.

The above researchers have found that GRPR mediates itch as a protection against puritic stimuli, but not pain. It was entirely unknown that Rexed Layer I was invovled in itch. Finding a peptide in the dorsal horn reinforces Marshall Devor’s communicatio to painonline that there are over a hundred peptides present in the synapses which have never been studied, suggesting that more pain peptide receptors may likely be implicated in pain transmission.

Why these chemicals come from the gut is anyone’s guess, but it teaches us that any signaller anywhere, in the blood vessels, gut, etc. must be evaluated as to noxious stimuli. It is a brave new world out there. Doctors are going to have to keep a very open mind as we thread out the peptide receptors which feed into the detection of and activation from noxious stimuli.

We have had a few respondencts to the survey who feel increased itch is part of their central pain. They are in the minority however. It is hard to distinguish itch from really minute pins and needles, so we may yet learn more about some link. In the past all pins and needles has been attributed to hyperpathia in the blodd vessels to very slight drops in oxygenation, but it may be that the picture is more complicated than we thought.

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