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Unlabelled: In certain patients with neuropathic pain, the pain is dependent on activity in the sympathetic nervous system. To investigate whether the spared nerve injury model (SNI) produced by injury to the tibial and common peroneal nerves and leaving the sural nerve intact is a model for sympathetically maintained pain, we measured the effects of surgical sympathectomy on the resulting mechanical allodynia, mechanical hyperalgesia, and cold allodynia. Decreases of paw withdrawal thresholds to von Frey filament stimuli and increases in duration of paw withdrawal to pinprick or acetone stimuli were observed in the ipsilateral paw after SNI, compared with their pre-SNI baselines. Compared with sham surgery, surgical lumbar sympathectomy had no effect on the mechanical allodynia and mechanical hyperalgesia induced by SNI. However, the sympathectomy significantly attenuated the cold allodynia induced by SNI. These results suggest that the allodynia and hyperalgesia to mechanical stimuli in the SNI model is not sympathetically maintained. However, the sympathetic nervous system may be involved, in part, in the mechanisms of cold allodynia in the SNI model., Perspective: The results of our study suggest that the SNI model is not an appropriate model of sympathetically maintained mechanical allodynia and hyperalgesia but may be useful to study the mechanisms of cold allodynia associated with sympathetically maintained pain states.

Unlabelled: Bone is a common metastatic site for prostate and breast cancer, and bone cancer is usually associated with severe pain. Traditional treatments for cancer pain can sometimes be ineffective or associated with side effects. Thus an increasing number of patients seek alternative therapies. In this study we investigated the analgesic effects of a soy diet on 3 experimental models of bone cancer pain. Mice were fed a diet in which the protein source was either soy or casein. After 1 week on the diet, sarcoma cells (NCTC 2472) were injected into the medullary cavity of the humeri, femur, or calcaneus. Experimenters blinded to diet of the animal assessed the pain behavior in these animals, forelimb grip force in the humerus model and paw withdrawal frequency to mechanical stimuli in the calcaneus and femur models. The effect of morphine on cancer-induced pain behavior was investigated in calcaneus and femur models. In addition, in the femur model, the effects of soy on tumor size and bone destruction were studied. The soy diet reduced secondary mechanical hyperalgesia in the femur model but had no effect on primary mechanical hyperalgesia in the calcaneus model or on movement-related hyperalgesia in the humerus model. No dietary impact was discerned in measurements of tumor size, bone destruction, and body weight in the femur model, suggesting that the soy diet had no effect on cancer growth. Morphine dose-dependently reduced hyperalgesia with no diet-based difference. These results suggest that a soy diet might provide analgesia in certain forms of hyperalgesia associated with bone cancer., Perspective: The study raises the possibility of dietary supplements influencing aspects of cancer pain. Further research will help determine if use of nutritional supplements, such as soy proteins, can reduce opioid analgesic use in chronic pain states and help minimize the side effects associated with long term use of opioids.