38 THE EFFECT OF DIET ON PAIN

Topical Seminar: WIRING AND RE-WIRING OF THE DORSAL HORN Dr. Rea will review the harmful effect of environmental pollutants such as solvents, pesticides and other volatile chemicals on the peripheral, central and autonomic nervous system. Dr. Rea will present data showing that the majority of affected people have pain and fatigue as their main symptoms. Toxicity can be identified in these patients by oral, inhaled and intradermal challenge. Clearing the body from these substances is possible. Dr. Rea’s will present data showing that 85% of the patients cleared of these toxins reported decreased pain levels although no analgesic medications were used. The last speaker will be Dr. Shir that will present an overview on the effect of dietary ingredients on nociception. Although investigated for its beneficial role in multiple ailments, relatively meager research has been done on the possible role of diet in attenuating pain. This research shows that dietary ingredients, including carbohydrates, amino- and fatty acids and vitamins and trace elements can attenuate acute and chronic pain in rodents. Diet induces its anti-nociceptive effect via mechanisms involving production and function of cytokines, incorporation of phospholipids into peripheral nerves membranes, manipulating excitatory amino-acids production, etc. Although hardly investigated in humans, Dr. Shir will present data showing that dietary ingredients, like soy, could play an analgesic role in humans with painful inflammatory and neuropathic conditions. 38 THE EFFECT OF DIET ON PAIN Y. Shir ° . Pain Centre, Department of Anesthesia, McGill University Health Centre, Montreal, Quebec, Canada Diet and dietary ingredients have been extensively investigated for their beneficial role in variety of ailments. Although less studied as analgesic modality, there is a growing body of evidence showing that dietary ingredients may be analgesic in experimental animals and in some pain conditions in humans. This presentation will review: (a) evidence from multiple laboratories, including ours, that basic dietary ingredients can attenuate acute and chronic nociception in animals, (b) evidence that dietary manipulation could suppress nociception in humans, and (c) possible mechanisms of dietary analgesia. Animal experiments showed that dietary components such as carbohydrates, amino- and fatty acids and dietary supplements were capable of attenuating pain and altering the responsiveness to opioids in multiple pain tests. Changing the sources of dietary fat and protein enabled attenuating or augmenting pain levels in pathological pain models of neuropathic and cancer pain: pain suppression was significantly associated with diets based on soy or corn protein and fat, but not with other dietary sources. In addition, a significant interaction was demonstrated between dietary fat and protein in their ability to suppress pain behavior. Although less investigated, it has been established that diet possesses analgesic properties in humans as well. This effect was attributed to certain diets in general (e.g., sweet-tasting foods and fluids), specific dietary sources (e.g., fish oil) or specific dietary ingredients (e.g., amino acids like tryptophan and arginine; vitamin C). Following our studies in rats we conducted a pilot study testing the analgesic role of soy diets in patients with chronic post-traumatic pain. Soy-rich diets were not only safe and well tolerated by chronic pain patients, but were also associated with partial analgesia, correlating the amounts of dietary soy. The mechanisms of dietary analgesia are not fully understood and could be mediated through the attenuation of the immune response to injury (e.g., changes in the production and function of cytokines), suppression of excitatory amino-acids and altered incorporation of phospholipids into peripheral nerve membranes. Our currently available analgesic tools fail to relieve pain in more than half of the patients with chronic pain. While dietary manipulation alone may not suffice to relieve pain, diet may serve as a useful adjunct in the treatment of painful conditions. More extensive research is needed, however, to establish the analgesic role of diet in acute and chronic pain conditions.

S11 39 THE EFFECT OF ENVIRONMENTAL TOXICITY ON PAIN W.J. Rea ° . USA Abstract not available at time of printing. 40 HERBS AND CHRONIC PAIN: PAST, PRESENT AND FUTURE? M.A. Ware ° . Departments of Anesthesia and Family Medicine, McGill University, Montreal, Quebec, Canada For millennia, mankind has turned to the plant world as a source of medicines. An increasing prevalence of chronic pain in Western societies coupled with a grumbling public mistrust of pharmaceutical medicines has resulted in renewed interest in plant-based pain therapies. The history of pharmaceutical pain management is not complete without considering the role of herbal remedies. Examples of modern pain medicines that have herbal origins include opioids (Papaver somniferum), salicylates (Salix alba), capsaicin (Capsicum spp.) and cannabinoids (Cannabis sativa). In most cases, isolated, purified and even synthetic extracts of these plants have resulted in the development of standardized preparations which have subsequently been subjected to rigourous evaluation in clinical trials. However raw herbal preparations are still available and the so-called natural products industry is booming. In this session these issues will be explored in reference to two main areas: 1. The recent development of novel drugs based on cannabis has not only led to new medicines but has also helped us uncover some of the neurophysiological mechanisms of pain modulation. Cannabinoid receptors and endogenous ligands offer new therapeutic targets, and evidence of analgesic effects is gradually being translated from basic to clinical research, particularly in the domain of central neuropathic pain. 2. Evidence is emerging for the efficacy of other herbal preparations (including willow bark, Devil’s claw, and omega-3 preparations); these data will be reviewed and safety issues (e.g. standardization, drug– herb interactions, toxicity) will be discussed. Reasons why patients may choose such remedies will be briefly explored, including the perception of natural therapies being safe and the alleged superiority of complex botanicals over single agent therapeutics. Potential avenues for research to explore the analgesic properties of herbal compounds will be discussed. It is clear that our plant environment has yielded safe and effective medicines in the past; and it is important that we continue to identify and harness the healing power of plants as we continue our struggle against the problem of pain.

Topical Seminar: WIRING AND RE-WIRING OF THE DORSAL HORN 41 Topical Seminar Summary: WIRING AND RE-WIRING OF THE DORSAL HORN J. Sandk¨uhler ° . Dept. of Neurophysiology, Center of Brain Research, Vienna, Austria Hyperalgesia and allodynia are in part due to long-term changes which occur at the level of spinal cord dorsal horn. While this is now a generally accepted concept, the impact of neuronal plasticity in spinal cord on dynamic processing of nociceptive information in reciprocal spinal-supraspinal loops is only beginning to unfold. The workshop will specifically address the delicate balance between spinal and supraspinal processing of pain-related information. In the first talk entitled “Population coding of nociceptive information by spinal cord lamina I neurons” Dr. Lima will provide evidence for a role for differential activation of the four structural groups of spinal lamina I projection neurons in coding nociceptive information. Lamina I activation levels are likely to be determined by reciprocal lamina I-supraspinal circuits in a cell-type specific