Effects of Distinct Force Magnitude of Spinal Manipulative Therapy on Blood Biomarkers of Inflammation: A Proof of Principle Study in Healthy Young Adults.

OBJECTIVES: The purpose of this preliminary study was to determine the influence of thoracic spinal manipulation therapy (SMT) of different force magnitudes on blood biomarkers of inflammation in healthy adults. METHODS: Nineteen healthy young adults (10 female, age: 25.6 ± 1.2 years) were randomized into the following 3 groups: (1) control (preload only), (2) single thoracic SMT with a total peak force of 400N, and (3) single thoracic SMT with a total peak force of 800N. SMT was performed by an experienced chiropractor, and a force-plate embedded treatment table (Force Sensing Table Technology) was used to determine the SMT force magnitudes applied. Blood samples were collected at pre intervention (baseline), immediately post intervention, and 20 minutes post intervention. A laboratory panel of 14 different inflammatory biomarkers (pro, anti, dual role, chemokine, and growth factor) was assessed by multiplex array. Change scores from baseline of each biomarker was used for statistical analysis. Two-way repeated-measures analysis of variance was used to investigate the interaction and main effects of intervention and time on cytokines, followed by Tukey's multiple comparison test (P ≤ .05). RESULTS: A between-group (800N vs 400N) difference was observed on interferon-gamma, interleukin (IL)-5, and IL-6, while a within-group difference (800N: immediately vs 20 minutes post-intervention) was observed on IL-6 only. CONCLUSION: In this study, we measured short-term changes in plasma cytokines in healthy young adults and found that select plasma pro-inflammatory and dual-role cytokines were elevated by higher compared to lower SMT force. Our findings aid to advance our understanding of the potential relationship between SMT force magnitude and blood cytokines and provide a healthy baseline group with which to compare similar studies in clinical populations in the future.

Spine-Adjusting Instrument (Impulse®) Attenuates Nociception and Modulates Oxidative Stress Markers in the Spinal Cord and Sciatic Nerve of a Rat Model of Neuropathic Pain.

OBJECTIVE: Oxidative stress plays an important role in neuropathic pain (NP). Spinal manipulative therapy (SMT) can exert beneficial effects on pain outcomes in humans and in animal models. SMT can also modulate oxidative stress markers in both humans and animals. We aimed to determine the effect of Impulse®-assisted SMT (ISMT) on nociception and oxidative stress biomarkers in the spinal cords and sciatic nerves of rats with NP. METHODS: NP was induced by chronic constriction injury (CCI) of the sciatic nerve. Animals were randomly assigned to naive, sham (rats with sciatic nerve exposure but without ligatures), or CCI, with and without ISMT. ISMT was applied onto the skin area corresponding to the spinous process of L4-L5, three times per week for 2 weeks. Mechanical threshold, latency to paw withdrawal in response to thermal stimulus, and oxidative stress biomarkers in the spinal cord and sciatic nerve were the main outcomes evaluated. RESULTS: ISMT significantly increased mechanical threshold and withdrawal latency after CCI. In the spinal cord, ISMT prevented the increase of pro-oxidative superoxide anion generation and hydrogen peroxide levels. Lipid hydroperoxide levels both in the spinal cord and in the sciatic nerve were attenuated by ISMT. Total antioxidant capacity increased in the spinal cords and sciatic nerves of CCI rats with and without ISMT. CCI and ISMT did not significantly change the total thiol content of the spinal cord. CONCLUSIONS: Our findings suggest that reduced oxidative stress in the spinal cord and/or nerve may be an important mechanism underlying a therapeutic effect of SMT to manage NP nonpharmacologically.

Whole-body vibration therapy does not improve the peripheral nerve regeneration in experimental model.

OBJECTIVES: Whole-body vibration (WBV) is commonly used to improve motor function, balance and functional performance, but its effects on the body are not fully understood. The main objective was to evaluate the morphometric and functional effects of WBV in an experimental nerve regeneration model. METHODS: Wistar rats were submitted to unilateral sciatic nerve crush and treated with WBV (4-5 weeks), started at 3 or 10 days after injury. Functional performances were weekly assessed by sciatic functional index, horizontal ladder rung walking and narrow beam tests. Nerve histomorphometry analysis was assessed at the end of the protocol. RESULTS: Injured groups, sedentary and WBV started at 3 days, had similar functional deficits. WBV, regardless of the start time, did not alter the histomorphometry parameters in the regeneration process. CONCLUSIONS: The earlier therapy did not change the expected and natural recovery after the nerve lesion, but when the WBV starts later it seems to impair function parameter of recovery.

Aqueous leaf extract from Luehea divaricata Mart. Modulates oxidative stress markers in the spinal cord of rats with neuropathic pain.

ETHNOPHARMACOLOGICAL RELEVANCE: Reactive oxygen species (ROS) play an important role in neuropathic pain (i.e., pain caused by lesion or disease of the somatosensory system). We showed previously that the aqueous extract prepared from Luehea divaricata leaves, a plant explored by native ethnic groups of Brazil to treat different pathologic conditions, exhibits good antioxidant activity and induces analgesia in rats with neuropathic pain (J Ethnopharmacol, 2020; 256:112761. doi: 10.1016/j.jep.2020.112761). The effect was comparable to that of gabapentin, a drug recommended as first-line treatment for neuropathic pain. However, increasing evidence has indicated the need to accurately determine the oxidative stress level of an individual before prescribing supplemental antioxidants. AIM OF THE STUDY: This study assessed the effects of the oral administration of aqueous extract from leaves of L. divaricata on the sciatic functional index (SFI) and spinal-cord pro-oxidant and antioxidant markers of rats with neuropathic pain. MATERIALS AND METHODS: Placement of four loose chromic thread ligatures around the sciatic nerve produced chronic constriction injury (CCI) of the sciatic nerve, a commonly employed animal model to study neuropathic pain. Aqueous extract from leaves of L. divaricata (100, 300, 500 and 1000 mg/kg), gabapentin (50 mg/kg) and aqueous extract (500 mg/kg) + gabapentin (30 mg/kg) were administrated per gavage daily for 10 or 35 days post-CCI. Antinociception was assessed using the von Frey test while SFI showed functional recovery post-nerve lesion throughout the experimental period. At days 10 and 35 post-surgery, the lumbosacral spinal cord and a segment of the injured sciatic nerve were dissected out and used to determine lipid hydroperoxide levels and total antioxidant capacity (TAC). The spinal cord was also used to determine superoxide anion generation (SAG), hydrogen peroxide (H2O2) levels and total thiol content. RESULTS: As expected, the extract, gabapentin and extract + gabapentin induced antinociception in CCI rats. While no significant functional recovery was found at 10 days post-CCI, a significant recovery was found in SFI of extract-treated CCI rats at 21 and 35 days post-CCI. A significant functional recovery was found already at day 10 post-CCI in gabapentin and gabapentin + extract-treated CCI rats. The extract treatment prevented increases in lipid hydroperoxides levels and TAC in injured sciatic nerve, which were found in this tissue of vehicle-treated rats at 10 days post-CCI. Extract also prevented an increase in SAG, H2O2 and lipid hydroperoxides levels in the spinal cord, which were elevated in this tissue of vehicle-treated rats at 10 and 35 days post-CCI. Extract also prevented a decrease in total thiol content and an increase in TAC in the spinal cord of CCI rats in these same time periods. CONCLUSIONS: Aqueous extract from L. divaricata leaves was demonstrated, for the first time, to improve SFI and modulate oxidative stress markers in injured sciatic nerve and spinal cord of CCI rats. Thus, the antinociceptive effect of the extract involves modulation of oxidative stress markers in injured sciatic nerve and spinal cord.

Aqueous extract from Luehea divaricata Mart. Leaves reduces nociception in rats with neuropathic pain.

ETHNOPHARMACOLOGICAL RELEVANCE: Luehea divaricata, popularly known in Brazil as "açoita-cavalo", has been widely explored by different ethnic groups native to Brazil to treat different pathologic conditions, including inflammatory pain. However, no report could be found on the effect that extract of L. divaricata has on neuropathic pain. This is an important topic because convergent and divergent mechanisms underlie inflammatory vs. neuropathic pain indicate that there may not always be a clear mechanistic delineation between these two conditions. AIM OF THE STUDY: The study aimed to determine antioxidant activity and macronutrient composition of aqueous extract from leaves of L. divaricata, and the effect of oral administration on nociception in rats with chronic constriction injury (CCI) of sciatic nerve-induced neuropathic pain, one of the most commonly employed animal models of neuropathic pain. MATERIALS AND METHODS: The antioxidant activity of the extract was evaluated by total phenolic content and DPPH, ABTS●+ and ORAC methods. Vitexin was determined by HPLC to show that the composition of the extract of the present study is similar to that used in previous studies with this genus. Total sugar and sucrose concentrations were assessed by the anthrone method, while glucose and triacilglycerides were determined using commercially available kits. Fructose concentration was calculated from values for total sugars, glucose and sucrose. Total protein was determined by Bradford assay. The effect on DNA strand breaking was investigated by inhibition of strand breaking of supercoiled DNA by hydroxyl radical. The antinociceptive effects of aqueous extract (100, 300, 500, and 1000 mg/kg, i.g.) were evaluated on thermal and mechanical thresholds for neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve in rats. We also compared the antinociceptive effect of the extract (500 mg/kg, i.g.) with that induced by gabapentin (50 mg/kg, i.g.), a first-line clinical treatment for neuropathic pain. The effect of co-administration of extract (500 mg/kg, i.g.) and low-dose gabapentin (30 mg/kg, i.g.) was also assessed. In addition, the effect of the extract on body weight, and blood and hepatic parameters were investigated to reveal possible side effects of treatment. RESULTS: The extract showed high content of total phenol; good reducing capacity for DPPH, ABTS●+ and ORAC assays; presence of vitexin; and a high capacity to inhibit strand breaking of supercoiled DNA. The predominant sugar was sucrose, followed by glucose and fructose. Total protein was greater than triacylglycerides, with the latter being present in a trace amount in the extract. The extract increased the thermal and mechanical thresholds, which was reduced by CCI. The antinociceptive effect was comparable to gabapentin and was also found after co-administration of extract and low-dose gabapentin. No significant change was found in body weight and blood and hepatic indicators after extract treatment. CONCLUSIONS: Aqueous extract from L. divaricata leaves was as effective as gabapentin at attenuating CCI-induced neuropathic pain, indicating for first time the therapeutic potential of this species for this type of pain.

Spinal Manipulation Therapy Improves Tactile Allodynia and Peripheral Nerve Functionality and Modulates Blood Oxidative Stress Markers in Rats Exposed to Knee-Joint Immobilization.

OBJECTIVE: The purpose of our study was to evaluate the effect of manually assisted lumbar spinal manipulation therapy on tactile allodynia, peripheral nerve functional recovery, and oxidative markers in rats exposed to knee immobilization-inducing hypersensitivity. METHODS: Tactile allodynia and sciatic, tibial, and peroneal functional indices were assessed before the knee joint immobilization, 24 hours after the knee cast removal, and 24 hours after 3 weeks of lumbar therapy with the Activator Adjusting Instrument, model 4 (AAI 4). Subsequently, the blood was collected from each rat, and oxidative markers such as lipid hydroperoxide levels; nitric oxide metabolites; and superoxide dismutase, catalase, and glutathione peroxidase activities were assessed. RESULTS: The AAI 4 improved the immobilization-induced allodynia and recovered the peripheral nerve functional indices impaired after knee immobilization. Immobilized rats treated with AAI 4 therapy presented a lack of significant changes in lipid hydroperoxides and nitric oxide metabolites in the plasma contrasting with rats that were kept freely in their cages, with no therapy applied, which presented elevated lipid hydroperoxides levels. Also, the antioxidant catalase enzymatic activity decreased in the blood of rats immobilized and treated with AAI 4. CONCLUSION: These results suggest that manually assisted lumbar spinal manipulation therapy modulates systemic oxidative stress, which possibly contributes to the analgesia and recovery of peripheral nerve functionality.

The metabolic and neuroinflammatory changes induced by consuming a cafeteria diet are age-dependent.

OBJECTIVES: To compare the effects of a palatable cafeteria diet on serum parameters and neuroinflammatory markers of young and aged female Wistar rats. METHODS: Three-month-old (young) and 18-month-old (aged) female Wistar rats had access to a cafeteria diet (Caf-Young, Caf-Aged) or a standard chow diet (Std-Young, Std-Aged). RESULTS: The Caf-Young group showed a higher food consumption, weight gain, visceral fat depot, serum insulin and leptin levels, and the insulin resistance index (HOMA-IR) than the Std-Young group. The Caf-Aged group exhibited an increase in interleukin-1 levels in the cerebral cortex and hippocampus. The number of GFAP-positive cells did not differ between the groups, but there was a diet effect in the cerebral cortex and an age effect in the hippocampus. Phospho-tau expression did not differ between the groups. DISCUSSION: The 3- and 18-month-old rats responded differently to a cafeteria diet. Insulin and leptin levels are elevated in young animals fed a cafeteria diet, whereas aged animals are prone to neuroinflammation (indicated by an increase in interleukin-1ß levels). A combination of hypercaloric diet and senescence have detrimental effects on the inflammatory response in the brain, which may predispose to neurological diseases.

Effects of Methanol Fraction from Leaves of Schinus terebinthifolius Raddi on Nociception and Spinal-Cord Oxidative Biomarkers in Rats with Neuropathic Pain.

We determined the antioxidant potential of fractions obtained from leaves of Schinus terebinthifolius, a medicinal plant known in Brazil as aroeira, to select the fraction with the best yield and antioxidant performance. These qualities were found in the methanol fraction (MeF), which was administered intraperitoneally (20 mg/kg/day) for 3 and 10 days to rats with chronic constriction injury (CCI) of the sciatic nerve, a model of neuropathic pain. The MeF increased the mechanical and thermal thresholds that had been lowered by CCI. In parallel, the lumbosacral spinal cord showed an increase in superoxide dismutase but a decrease in glutathione peroxidase and glutathione-S-transferase activities in saline- and MeF-treated CCI rats. Catalase activity decreased only in saline-treated CCI rats for 10 days. Total thiols decreased in saline- and MeF-treated CCI rats. Ascorbic acid increased in these rats at day 3 but only in saline-treated CCI rats at day 10. No change was found in hydrogen peroxide and lipid hydroperoxide. Open-field and elevated plus-maze tests and blood parameters of liver function did not change. Thus, the MeF from leaves of S. terebinthifolius has an antinociceptive action with no toxic effects, and it affects oxidant biomarkers in the spinal cord of rats with CCI.

Epitestosterone- and testosterone-replacement in immature castrated rats changes main testicular developmental characteristics.

Epitestosterone is the 17α-epimer of testosterone and has been described as an anti-androgen, since it inhibits the effects produced by testosterone and dihydrotestosterone via the nuclear androgen receptor (nAR). However, epitestosterone also displays an effect which is similar to the non-classical effect of testosterone, depolarizing the membrane potential of Sertoli cells and inducing a rapid Ca2+ uptake. This study aimed to investigate the effects of a treatment with epitestosterone on developmental parameters of immature rats. Animals were chemically castrated by using the gonadotropin-releasing hormone (GnRH) antagonist cetrorelix and then received a replacement of 7 days with epitestosterone or testosterone. Replacement with either epitestosterone or testosterone restored the anogenital distance (AGD) and testicular weight which had been reduced by chemical castration. The immunocontent of nAR and the nAR-immunoreactivity were reduced by epitestosterone treatment in the testis of both castrated and non-castrated animals. Furthermore, testosterone was unable of changing the membrane potential of Sertoli cells through its non-classical action in the group of animals castrated and replaced with epitestosterone. In conclusion, in relation to the level of protein expression of nAR epitestosterone acts as an anti-androgen. However, it acts in the same way as testosterone when genital development parameters are evaluated. Moreover, in castrated rats epitestosterone suppressed the non-classical response of testosterone, changing the pattern of testosterone signalling via a membrane mechanism in Sertoli cells.

Methionine Administration in Pregnant Rats Causes Memory Deficit in the Offspring and Alters Ultrastructure in Brain Tissue.

In the present work, we evaluated the effect of gestational hypermethioninemia on locomotor activity, anxiety, memory, and exploratory behavior of rat offspring through the following behavior tests: open field, object recognition, and inhibitory avoidance. Histological analysis was also done in the brain tissue of pups. Wistar female rats received methionine (2.68 µmol/g body weight) by subcutaneous injections during pregnancy. Control rats received saline. Histological analyses were made in brain tissue from 21 and 30 days of age pups. Another group was left to recover until the 30th day of life to perform behavior tests. Results from open field task showed that pups exposed to methionine during intrauterine development spent more time in the center of the arena. In the object recognition memory task, we observed that methionine administration during pregnancy reduced total exploration time of rat offspring during training session. The test session showed that methionine reduced the recognition index. Regarding to inhibitory avoidance task, the decrease in the step-down latency at 1 and 24 h after training demonstrated that maternal hypermethioninemia impaired short-term and long-term memories of rat offspring. Electron microscopy revealed alterations in the ultrastructure of neurons at 21 and 30 days of age. Our findings suggest that the cell morphological changes caused by maternal hypermethioninemia may be, at least partially, associated to the memory deficit of rat offspring.

Systemic administration of vitamins C and E attenuates nociception induced by chronic constriction injury of the sciatic nerve in rats.

Antioxidants have been tested to treat neuropathic pain, and α-Tocopherol (vitamin E--vit. E) and ascorbic acid (vitamin C--vit. C) are potent antioxidants. We assessed the effect of intraperitoneal administration of vit. C (30 mg/kg/day) and vit. E (15 mg/kg/day), given alone or in combination, on the mechanical and thermal thresholds and the sciatic functional index (SFI) in rats with chronic constriction injury (CCI) of the sciatic nerve. We also determined the lipid hydroperoxides and total antioxidant capacity (TAC) in the injured sciatic nerve. Further, we assessed the effects of oral administration of vit. C+vit. E (vit. C+E) and of a combination of vit. C+E and gabapentin (100mg/kg/day, i.p.) on the mechanical and thermal thresholds of CCI rats. The vitamins, whether administered orally or i.p., attenuated the reductions in the mechanical and thermal thresholds induced by CCI. The antinociceptive effect was greater with a combination of vit. C+E than with each vitamin given alone. The SFI was also improved in vitamin-treated CCI rats. Co-administration of vit. C+E and gabapentin induced a greater antinociceptive effect than gabapentin alone. No significant change occurred in TAC and lipid hydroperoxide levels, but TAC increased (45%) while lipid hydroperoxides decreased (38%) in the sciatic nerve from vit. C+E-treated CCI rats. Thus, treatment with a combination of vit. C+E was more effective to treat CCI-induced neuropathic pain than vitamins alone, and the antinociceptive effect was greater with co-administration of vit. C+E and gabapentin than with gabapentin alone.

Peripheral oxidative stress blood markers in patients with chronic back or neck pain treated with high-velocity, low-amplitude manipulation.

OBJECTIVE: The purpose of this study was to investigate oxidative-stress parameters in individuals with chronic neck or back pain after 5 weeks of treatment with high-velocity, low-amplitude (HVLA) spinal manipulation. METHODS: Twenty-three individuals aged 38.2 ± 11.7 years with nonspecific chronic neck or back pain verified by the Brazilian Portuguese version of the Chronic Pain Grade, with a sedentary lifestyle, no comorbidities, and not in adjuvant therapy, underwent treatment with HVLA chiropractic manipulation twice weekly for 5 weeks. Therapeutic procedures were carried out by an experienced chiropractor. Blood samples were assessed before and after treatment to determine the activities of the antioxidant enzymes superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx), and the levels of nitric oxide metabolites and lipid hydroperoxides. These blood markers were analyzed by paired Student t test. Differences were considered statistically significant, when P was <.05. RESULTS: There was no change in catalase but an increase in SOD (0.35 ± 0.03 U SOD per milligram of protein vs 0.44 ± 0.04 U SOD per milligram of protein; P < .05) and GPx (7.91 ± 0.61 nmol/min per milligram of protein vs 14.07 ± 1.07 nmol/min per milligram of protein; P < .001) activities after the treatment. The nitric oxide metabolites and the lipid hydroperoxides did not change after treatment. CONCLUSION: High-velocity, low-amplitude spinal manipulation twice weekly for 5 weeks increases the SOD and GPx activities. Previous studies have shown a relationship between pain and oxidative and nitrosative parameters; thus, it is possible that changes in these enzymes might be related to the analgesic effect of HVLA spinal manipulation.

The protective effect of N-acetylcysteine on oxidative stress in the brain caused by the long-term intake of aspartame by rats.

Long-term intake of aspartame at the acceptable daily dose causes oxidative stress in rodent brain mainly due to the dysregulation of glutathione (GSH) homeostasis. N-Acetylcysteine provides the cysteine that is required for the production of GSH, being effective in treating disorders associated with oxidative stress. We investigated the effects of N-acetylcysteine treatment (150 mg kg(-1), i.p.) on oxidative stress biomarkers in rat brain after chronic aspartame administration by gavage (40 mg kg(-1)). N-Acetylcysteine led to a reduction in the thiobarbituric acid reactive substances, lipid hydroperoxides, and carbonyl protein levels, which were increased due to aspartame administration. N-Acetylcysteine also resulted in an elevation of superoxide dismutase, glutathione peroxidase, glutathione reductase activities, as well as non-protein thiols, and total reactive antioxidant potential levels, which were decreased after aspartame exposure. However, N-acetylcysteine was unable to reduce serum glucose levels, which were increased as a result of aspartame administration. Furthermore, catalase and glutathione S-transferase, whose activities were reduced due to aspartame treatment, remained decreased even after N-acetylcysteine exposure. In conclusion, N-acetylcysteine treatment may exert a protective effect against the oxidative damage in the brain, which was caused by the long-term consumption of the acceptable daily dose of aspartame by rats.

Evaluation of peak force of a manually operated chiropractic adjusting instrument with an adapter for use in animals.

OBJECTIVE: This study was designed to assess the peak force of a manually operated chiropractic adjusting instrument, the Activator Adjusting Instrument 4 (AAI 4), with an adapter for use in animals, which has a 3- to 4-fold smaller contact surface area than the original rubber tip. METHODS: Peak force was determined by thrusting the AAI 4 with the adapter or the original rubber tip onto a load cell. First, the AAI 4 was applied perpendicularly by a doctor of chiropractic onto the load cell. Then, the AAI 4 was fixed in a rigid framework and applied to the load cell. This procedure was done to prevent any load on the load cell before the thrust impulse. In 2 situations, trials were performed with the AAI 4 at all force settings (settings I, II, III, and IV, minimum to maximum, respectively). A total of 50000 samples per second over a period of 3 seconds were collected. RESULTS: In 2 experimental protocols, the use of the adapter in the AAI 4 increased the peak force only with setting I. The new value was around 80% of the maximum value found for the AAI 4. Nevertheless, the peak force values of the AAI 4 with the adapter and with the original rubber tip in setting IV were similar. CONCLUSION: The adapter effectively determines the maximum peak force value at force setting I of AAI 4.

Effect of N-acetylcysteine on the spinal-cord glutathione system and nitric-oxide metabolites in rats with neuropathic pain.

Since N-acetylcysteine (NAC) is a donor of cysteine, we studied the relationship between NAC and concentration of oxidized and reduced glutathione (GSH/GSSG ratio), and glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities in the lumbosacral spinal cord of rats with chronic constriction injury (CCI) of the sciatic nerve that received NAC (150mg/kg/day, i.p.) or 0.9% saline solution for 3 or 10 days. Hydrogen peroxide (H2O2) and nitric-oxide (NO) metabolites were also measured. Von Frey hair and hot-plate tests showed hyperalgesia at day 1 in CCI rats. Hyperalgesia persisted at all other times in saline-treated CCI rats, but returned to pre-injury values in NAC-treated CCI rats after 3 postoperative days. GST activity and the GSH/GSSG ratio increased in saline-treated CCI rats, while the NAC treatment increased GST and GPx activities at day 10, with no significant change in the GSH/GSSG ratio. NAC treatment did not affect H2O2 levels, but it reduced NO metabolites in CCI rats 3 days after the surgery. Thus, the anti-hyperalgesic effect of NAC appears not to involve its action as a cysteine precursor for GSH synthesis, but involves a decrease in NO.

N-acetylcysteine protects the rat kidney against aspartame-induced oxidative stress.

Long-term intake of aspartame at the acceptable daily ingestion dose causes oxidative stress in the rat kidney through the dysregulation of glutathione homeostasis. N-acetylcysteine (NAC) provides the cystein required for the production of GSH, being effective in treating disorders associated with oxidative stress. The aim of this research was to investigate the effects of NAC on the aspartame-induced oxidative stress in the rat kidney. The animals received aspartame by gavage for six weeks (40mg/kg). From the 5th week, NAC (1mmol/kg, via intraperitoneal) was injected for two weeks. Then, they were anaesthetized for blood sample and euthanized for the kidney collection. The blood was centrifuged at 1800g for 15min and the serum was separated for creatinine measurement. The tissue was homogenized in 1.15% KCl buffer and centrifuged at 700g for 10min at 4°C. The supernatant fraction obtained was used to the measurements of oxidative stress biomarkers. The creatinine levels were enhanced in the serum of aspartame-treated rats. NAC caused a reduction in the thiobarbituric acid reactive substances, lipid hydroperoxides, carbonyl protein and hydrogen peroxide levels, which were increased in the kidney of aspartame-treated animals. Additionally, NAC caused an elevation in the glutathione peroxidase and glutathione reductase activities, total glutathione, ascorbic acid, and total reactive antioxidant potential levels, which were decreased in the kidney of aspartame-treated rats. In conclusion, NAC may be useful for the protection of the rat kidney against aspartame-induced oxidative stress.

Sciatic nerve transection modulates oxidative parameters in spinal and supraspinal regions.

Neuropathic pain is a very common dysfunction caused by several types of nerve injury. This condition leads to a variety of pathological changes in central nervous system regions related to pain transmission. It has been demonstrated that nociception is modulated by reactive oxidative species and treatments with antioxidant compounds produce antinociceptive effects. Thus, the aim of the present study was to investigate oxidative parameters in spinal and supraspinal regions following sciatic nerve transection (SNT). In behavioral assessments, animals showed mechanical allodynia and a significant functional impairment following SNT, measured by von Frey hairs test and sciatic functional index, respectively. Superoxide dismutase activity was increased 3 and 7 days following SNT in cerebral cortex and brainstem. Catalase activity was also increased in cerebral cortex 3 days after SNT. Ascorbic acid levels were decreased 7 days in the spinal cord only in SNT group. We also showed an increase in lipid peroxidation in cerebral cortex and brainstem 3 days after surgery in SNT and sham groups. These results showed that supraspinal regions also exhibit changes in antioxidant activity after SNT and demonstrate an intricate relationship among antioxidant defenses in different regions of the neuro axis related to pain transmission.

After-effects of consecutive sessions of transcranial direct current stimulation (tDCS) in a rat model of chronic inflammation.

Transcranial direct current stimulation (tDCS) induces cortical excitability changes in animals and humans that can last beyond the duration of stimulation. Preliminary evidence suggests that tDCS may have an analgesic effect; however, the timing of these effects, especially when associated with consecutive sessions of stimulation in a controlled animal experiment setting, has yet to be fully explored. To evaluate the effects of tDCS in inflammatory chronic pain origin immediately and 24 h after the last treatment session, complete Freund's adjuvant (CFA) was injected (100 µl) in the right footpad to induce inflammation. On the 15th day after CFA injection, rats were divided into two groups: tDCS (n = 9) and sham (n = 9). The tDCS was applied for 8 days. The hot plate and Von Frey tests were applied immediately and 24 h after the last tDCS session. Eight 20-min sessions of 500 µA anodal tDCS resulted in antinociceptive effects as assessed by the hot plate test immediately (P = 0.04) and 24 h after the last tDCS session (P = 0.006), for the active tDCS group only. There was increased withdrawal latency in the Von Frey test at 24 h after the last session (P = 0.01). Our findings confirm the hypothesis that tDCS induces significant, long-lasting, neuroplastic effects and expands these findings to a chronic pain model of peripheral inflammation, thus supporting the exploration of this technique in conditions associated with chronic pain and peripheral inflammation, such as osteoarthritis.

Assessment of oxidative parameters in rat spinal cord after chronic constriction of the sciatic nerve.

Although reactive oxygen species (ROS) are involved in neuropathic pain, the direct relationship between these species and chronic constriction of sciatic nerve (CCI) has not been studied in spinal cord. Thus, this study induced CCI in rats and these animals were sacrificed 3 and 10 days after the surgical procedure to determine the superoxide dismutase (SOD) and catalase activities, as well as ascorbic acid, hydrogen peroxide (H(2)O(2)) and lipid hydroperoxide levels in lumbosacral spinal cord. Von Frey Hair and hot plate tests were performed to assess the degree of mechanical and thermal hyperalgesia at days 0, 3 and 10. The results showed that CCI significantly induced mechanical and thermal hyperalgesia at days 3 and 10. Parallel there was increase in spinal cord lipid hydroperoxide at days 3 and 10 in rats submitted to CCI. In Sham rats a significant increase in this parameter occurred at day 10. H(2)O(2) decreased at day 10 only in CCI group. SOD activity was decreased in Sham and CCI groups at day 3, while catalase activity was increased in CCI rats at days 3 and 10. Ascorbic acid levels were reduced only in CCI rats at day 3. Although the role of such changes is unclear, many were not specific to neuropathic pain and the differences could be related to different degrees of central sensitization in Sham and CCI rats.

Effect of high-velocity, low-amplitude treatment on superoxide dismutase and glutathione peroxidase activities in erythrocytes from men with neck pain.

OBJECTIVE: This study investigates the analgesic effect of high-velocity, low-amplitude (HVLA) manipulation and antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GPx) in erythrocytes of men with neck pain. METHODS: Twenty-two men with neck pain of mechanical origin who were aged 20 to 50 years, were nonsmokers, had a sedentary lifestyle, had no comorbidities, and were not in adjuvant therapy underwent 6 sessions of HVLA chiropractic manipulation 3 times a week for 2 weeks. Patients were treated by the same chiropractor and under the same conditions. Blood samples were collected before the beginning of the treatment and at the end of the third and last session. Erythrocytes were separated from blood and then processed to determine SOD and GPx activities. The quadruple visual scale and the Neck Disability Index were used to demonstrate the analgesic effect of treatment. The results were analyzed by repeated-measures analysis of variance followed by Bonferroni posttest. Differences were considered significant when P was less than .05. RESULTS: Despite the tendency to reduction in SOD and increase in GPx activities, there was no significant change after the treatment. CONCLUSION: High-velocity, low-amplitude treatment for 6 sessions in men with neck pain did not affect systemic SOD and GPx activities. Despite the absence of significant changes, this study is important because it is the first to investigate the activities of SOD and GPx in patients with neck pain treated with HVLA spinal manipulation.