Scientists from Johns Hopkins and two Israeli universities have discovered another likely benefit of the much-touted legume, soybeans: They may bring pain relief. A new study shows that laboratory rats fed a diet containing soy meal develop far less pain after nerve injury than their counterparts on soy-free diets.

"In people, strong individual differences exist in the perception of pain," says Hopkins neurosurgeon James N. Campbell, M.D., one of the researchers. "And while this is undoubtedly due to a number of factors, the idea that diet could affect the pain experience offers fascinating possibilities for understanding our vulnerability to it." Enough similarities exist between rats and humans in the biology of pain perception, Campbell says, to make them useful models.

The study, reported initially in a recent issue of the journal Neuroscience Letters, and since supported by additional research, arose from unusual circumstances, Campbell says, when visiting Israeli neuroscientist Yoram Shir of the Hebrew University of Jerusalem came to Hopkins to further study an animal model for pain he'd previously created with collaborators.

Shir's rats were treated to simulate serious painful syndromes that can follow nerve injury in humans. Patients can develop a heightened sensitivity to touch and temperature such that these normally mild stimuli cause pain.

Using anesthetized rats in which the sciatic nerve to one foot is partly severed surgically, the Israeli researchers measured sensitivity to pain by touching the foot with fine probes of varied size.

But when Shir tried to duplicate his model at Hopkins, most of the laboratory rats showed no heightened sensitivity to pain. "We were mystified," says Campbell.

Led by Shir, the research team then systematically tested every possible source of difference in the model, from the strain of rat to possible changes in surgical technique --
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Contact: Marjorie Centofanti
mcentofanti@jhmi.edu
410-955-8725
Johns Hopkins Medical Institutions
25-Jan-1999