Soy-containing diet suppresses chronic neuropathic sensory disorders in rats

Partial sciatic nerve ligation (PSL) in rodents produces chronic neuropathic sensory disorders resembling neuropathic pain in humans. We previously reported that levels of allodynia and hyperalgesia after PSL injury were markedly attenuated by consumption of soy-containing diets. Here we aimed to show that dietary effect on pain behavior is not specific to a certain laboratory. For this purpose, experiments were conducted in a different laboratory (Baltimore rather than Jerusalem) and a different rat strain (Wistar rather than Sabra), with additional and different testing methods (radiant heat from a lamp rather than a CO(2) laser). Rats were fed two soy-free diets and a soy-containing one for 28 days. The sensitivity of rats to nonnoxious and noxious stimuli was determined before PSL injury, and levels of neuropathic sensory disorders were determined after it. We found that consuming the soy-containing diet prevented development of tactile and heat allodynia, but not mechanical hyperalgesia. This dietary effect was not correlated with calorie intake and weight gain or dietary concentration of fat and carbohydrates. We conclude that, regardless of experimental site, diet markedly affects chronic neuropathic sensory disorders in rats and should be standardized in animal models of pain.

Levels of chronic sensory disorders in a rat model of allodynia and hyperalgesia after partial sciatic nerve ligation depend on the consumption of a soy-containing diet. Further studies are needed to determine the role of diet in humans with chronic pain.