"Long before it's in the papers"
December 12, 2013

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Scientists developing way to “see” pain in the body

Dec. 12, 2013
Courtesy of the American Chemical Society
and World Science staff

Sci­en­tists are hop­ing a new tech­nique will let them “see” pain in the bod­ies of hurt­ing peo­ple, so doc­tors won’t have to rely solely on pa­tients’ some­times un­clear ac­counts of their own pain.

Past re­search has shown a link be­tween pain and a cer­tain kind of mol­e­cule in the body, called a so­di­um chan­nel—a pro­tein that helps nerve cells trans­mit pain and oth­er sensa­t­ions to the brain. Cer­tain types of so­di­um chan­nel are over-pro­duced at the site of an in­ju­ry. So re­search­ers set out to de­vel­op a way to make the re­sult­ing over-concentra­t­ions of so­di­um chan­nels vis­i­ble in scan­ning im­ages.

Cur­rent ways to di­ag­nose pain bas­ic­ally in­volve ask­ing the pa­tient if some­thing hurts. This can lead doc­tors astray for a va­ri­e­ty of rea­sons, in­clud­ing if a pa­tient can’t com­mu­ni­cate well or does­n’t want to talk about the pain. It can al­so be hard to tell how well a treat­ment is really work­ing. 

No ex­ist­ing meth­od can meas­ure pain in­tens­ity ob­jec­tively or help physi­cians pin­point where the pain is, said Sandip Biswal of Stan­ford Uni­vers­ity in Cal­i­for­nia and col­leagues, who de­scribed their new tech­nique Nov. 21 on­line in the Jour­nal of the Amer­i­can Chem­i­cal So­ci­e­ty. 

Biswal and col­leagues tested the tech­nique in rats.

They used an ex­ist­ing scan­ning meth­od known as pos­i­tron emis­sion to­mog­ra­phy (PET) scan, which uses a harm­less ra­di­o­ac­t­ive sub­stance called a trac­er to look for dis­ease in the body. They al­so turned to a small mol­e­cule called sax­i­toxin, pro­duced nat­u­rally by cer­tain types of mi­cro­scop­ic ma­rine crea­tures, and at­tached a sig­nal to it so they could trace it by PET im­ag­ing.

When the re­search­ers in­jected the mol­e­cule in­to rats, of­ten a stand-in for hu­mans in lab tests, they saw that the mol­e­cule ac­cu­mu­lat­ed where the rats had nerve dam­age. The rats did­n’t show signs of tox­ic side ef­fects, the sci­en­tists said, adding that the work is one of the first at­tempts to mark these so­di­um chan­nels in a liv­ing an­i­mal.


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Scientists are hoping a new technique will let them “see” pain in the bodies of hurting people, so doctors won’t have to rely solely on patients’ sometimes unclear accounts of their own pain. Past research has shown a link between pain and a certain kind of molecule in the body, called a sodium channel—a protein that helps nerve cells transmit pain and other sensations to the brain. Certain types of sodium channel are over-produced at the site of an injury. So researchers set out to develop a way to make the resulting over-concentrations of sodium channels visible in scanning images. Current ways to diagnose pain basically involve asking the patient if something hurts. This can lead doctors astray for a variety of reasons, including if a patient can’t communicate well or doesn’t want to talk about the pain. It can also be hard to tell how well a treatment is really working. No existing method can measure pain intensity objectively or help physicians pinpoint where the pain is, said Sandip Biswal of Stanford University in California and colleagues, who described their new technique Nov. 21 online in the Journal of the American Chemical Society. Biswal and colleagues tested the technique in rats. They used an existing scanning method known as positron emission tomography (PET) scan, which uses a harmless radioactive substance called a tracer to look for disease in the body. They also turned to a small molecule called saxitoxin, produced naturally by certain types of microscopic marine creatures, and attached a signal to it so they could trace it by PET imaging. When the researchers injected the molecule into rats, often a stand-in for humans in lab tests, they saw that the molecule accumulated where the rats had nerve damage. The rats didn’t show signs of toxic side effects, the scientists said, adding that the work is one of the first attempts to mark these sodium channels in a living animal.