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Unlabelled: Certain dietary proteins and oils are capable of decreasing chronic neuropathic pain levels in rats after partial sciatic nerve ligation injury. We tested, for the first time, the role of dietary polyunsaturated fatty acids in suppressing pain in partial sciatic nerve ligation-injured rats. Six groups of male Wistar rats were fed an identical casein-based, fat-free diet for 1 wk preceding partial sciatic nerve ligation injury and for 1 wk thereafter. In addition, rats received, via gavage, 1 mL/day of pure canola, corn, hemp, soy, or sunflower oil, differing significantly in their omega-3 and omega-6 polyunsaturated fatty acid content, or 1 mL of plain water. Responses to tactile and noxious heat stimuli were recorded before and after surgery and a difference score was calculated for each group by subtracting the preoperative from the post-partial sciatic nerve ligation values. Heat hyperalgesia, but not tactile allodynia, was significantly different among the dietary groups (P = 0.005). Heat hyperalgesia of rats fed hemp oil, developing the most robust response, was significantly larger compared with rats fed corn oil, developing the least pain model (difference score: 24.3 +/- 4.1 s versus 6.1 +/- 3.1 s, respectively; P < 0.001). These oils contain similar levels of omega-6 polyunsaturated fatty acids (hemp, 60%; corn, 58%) but their omega-3 levels are 28-fold different (20% versus 0.7%, respectively). A significant correlation was found among dietary levels of omega-3, but not omega-6 or the omega-3/omega-6 ratio, of the six dietary groups and heat hyperalgesia (P = 0.006). We conclude that dietary oil might predict levels of neuropathic pain in rats and that this effect may be associated with dietary omega-3 levels., Implications: We found that certain commonly used oils can have a significant analgesic effect in rats with persistent pain after partial nerve injury. This effect may be associated with the amounts of omega-3 fatty acids consumed by rats.

Chronic neuropathic sensory disorders (CNSD) of rats receiving a partial sciatic nerve ligation injury (the PSL model) are suppressed by dietary soy protein. Although previously shown to modify nociceptive behavior in acute pain models, dietary fat has never been tested for its putative analgesic properties in chronic pain states. Here we tested the role of dietary fat, protein and fat/protein interactions in the development of tactile allodynia and heat hyperalgesia in PSL-injured rats. Male Wistar rats were fed nine different diets, comprising of three proteins (soy, casein and albumin) and three fats (corn, soy and canola) for a week preceding PSL injury and for 2 weeks thereafter. Rats' responses to tactile and noxious heat stimuli were tested before surgery and 3, 7 and 14 days afterwards. Tactile and heat sensory abnormalities following PSL injury were significantly different among the nine dietary groups. Consumption of corn and soy fats suppressed the levels of tactile and heat allodynia and hyperalgesia, whereas consumption of soy and casein proteins was associated with lower levels of heat hyperalgesia but not tactile allodynia. A significant fat/protein interaction was found for the heat but not tactile stimuli. We conclude that dietary fat is a significant independent predictor of levels of neuropathic sensory disorders in rats and that this effect is accentuated by dietary protein. The mechanisms by which fat suppresses neuropathic disorders have yet to be determined.

Objective: Good pain control is a prerequisite for success in the management of many rheumatological diseases. However, some rheumatology patients may present challenges in terms of pain management and be subsequently referred to a specialized pain clinic. We examined the characteristics and assessed the outcome of patients with rheumatic diseases who were referred to a tertiary care pain center., Methods: All new patients with a primary rheumatological diagnosis referred over a 9 year period to the McGill University Pain Centre were studied. Patients were identified through a computer search according to both diagnoses and symptoms. Demographic information, clinical and pain characteristics, and subsequent management and final outcome were assessed., Results: Out of a total of 1120 new patients, 60 (5%) had a primary rheumatologic diagnosis to account for pain and referral. The diagnoses were as follows: fibromyalgia in 26 (43%), inflammatory arthritis 17 (28%), degenerative arthritis 9 (15%), and soft tissue rheumatism 8 (13%). The median age at presentation was 52 years and 47 (78%) were female. The median duration of pain was 5 years. The mean pain scores according to the McGill Pain Questionnaire and the visual analog scale were 27 +/- 15 and 7 +/- 2, respectively. Patients were followed a mean duration of 10.6 +/- 15 months. Seventy-two percent were assessed by a psychologist and 52% by a physiotherapist or occupational therapist. New pharmacologic treatments were prescribed for 47 (78%) patients, with 47% receiving opioids, 37% antidepressants, 12% nonsteroidal antiinflammatory drugs, 8% tranquillizers, and 18% other medications. Final outcome was described as follows: improved in 55%, no change in 43%, and worsened in 2%., Conclusion: Although patients with a primary rheumatologic process to account for pain constituted a small proportion of patients evaluated, improvement was considerable in over half. Further study should address the selection of patients that are most likely to benefit from referral to multidisciplinary pain centers and the longterm outcome of such interventions.

There has been a surge in interest in medicinal cannabis in Canada. We conducted a questionnaire survey to determine the current prevalence of medicinal cannabis use among patients with chronic non-cancer pain, to estimate the dose size and frequency of cannabis use, and to describe the main symptoms for which relief was being sought. Over a 6-week period in mid-2001, 209 chronic non-cancer pain patients were recruited in an anonymous cross-sectional survey. Seventy-two (35%) subjects reported ever having used cannabis. Thirty-two (15%) subjects reported having used cannabis for pain relief (pain users), and 20 (10%) subjects were currently using cannabis for pain relief. Thirty-eight subjects denied using cannabis for pain relief (recreational users). Compared to never users, pain users were significantly younger (P=0.001) and were more likely to be tobacco users (P=0.0001). The largest group of patients using cannabis had pain caused by trauma and/or surgery (51%), and the site of pain was predominantly neck/upper body and myofascial (68% and 65%, respectively). The median duration of pain was similar in both pain users and recreational users (8 vs. 7 years; P=0.7). There was a wide range of amounts and frequency of cannabis use. Of the 32 subjects who used cannabis for pain, 17 (53%) used four puffs or less at each dosing interval, eight (25%) smoked a whole cannabis cigarette (joint) and four (12%) smoked more than one joint. Seven (22%) of these subjects used cannabis more than once daily, five (16%) used it daily, eight (25%) used it weekly and nine (28%) used it rarely. Pain, sleep and mood were most frequently reported as improving with cannabis use, and 'high' and dry mouth were the most commonly reported side effects. We conclude that cannabis use is prevalent among the chronic non-cancer pain population, for a wide range of symptoms, with considerable variability in the amounts used. Discussions between patients and health care providers concerning cannabis use may facilitate education and follow up, and would allow side effects and potential interactions with other medications to be monitored. Clinical trials of cannabis for chronic non-cancer pain are warranted.

This study investigated the feasibility of bonding layers of porcine small intestinal submucosa (SIS, Cook Biotech, Inc.) with a light-activated protein solder. SIS is an acellular, collagen-based extracellular matrix material that is approximately 100 microns thick. The solder consists of bovine serum albumin and indocyanine green dye (ICG) in deionized water. The solder is activated by an 808 nm diode laser, which denatures the albumin, causing the albumin to bond with the collagen of the tissue. The predictable absorption and thermal energy diffusion rates of ICG increase the chances of reproducible results. To determine the optimal condition for laser soldering SIS, the following parameters were varied: albumin concentration (from 30-45% (w/v) in increments of 5%), the concentration of ICG (from 0.5-2.0 mg/ml H2O) and the irradiance of the laser (10-64 W/cm2). While many of the solder compositions and laser irradiance combinations resulted in no bonding, a solder composition of 45% albumin, ICG concentration of 0.5 mg/ml H2O, and a laser irradiance of 21 W/cm2 did produce a bond between two pieces of SIS. The average shear strength of this bond was 29.5 +/- 17.1 kPa (n = 14). This compares favorably to our previous work using fibrin glue as an adhesive, in which the average shear strength was 27 +/- 15.8 kPa (n = 40).

Background: Chronic pain is one of the most common reasons for therapeutic cannabis use., Objectives: To describe therapeutic cannabis use among patients with chronic pain., Methods: Patients with chronic pain who voluntarily indicated that they used cannabis therapeutically completed a questionnaire about the type of cannabis used, the mode of administration, the amount used and the frequency of use, and their perception of the effectiveness of cannabis on a set of pain-associated symptoms and side effects. The study was approved by the McGill University Health Centre Research Ethics Board., Results: Fifteen patients (10 male) were interviewed (median age 49.5 years, range 24 to 68 years). All patients smoked herbal cannabis for therapeutic reasons (median duration of use six years, range two weeks to 37 years). Seven patients only smoked at night-time (median dose eight puffs, range two to eight puffs), and eight patients used cannabis mainly during the day (median dose three puffs, range two to eight puffs); the median frequency of use was four times per day (range one to 16 times per day). Twelve patients reported improvement in pain and mood, while 11 reported improvement in sleep. Eight patients reported a 'high'; six denied a 'high'. Tolerance to cannabis was not reported., Conclusions: The results of this self-selected case series must be interpreted with caution. Small doses of smoked cannabis may improve pain, mood and sleep in some patients with chronic pain. Clinical trials are warranted to test these effects. Further prospective studies should examine the patterns and prevalence of cannabis use among chronic pain populations.