Effects of Swimming on the Inflammatory and Redox Response in a Model of Allergic Asthma.

In this study we hypothesized that swimming during sensitization phase could result in a preventive effect in mice with allergic asthma. Swiss mice were divided into 4 groups: Control and Swimming (non-sensitized), OVA and OVA+Swimming (sensitized). The allergic inflammation was induced by 2 intraperitoneal injections and 4 aerosol challenges using ovalbumin. Swimming sessions were performed at high intensity over 3 weeks. 48 h after the last challenge mice were euthanized. Swimming decreased OVA-increased total IgE, IL-1, IL-4, IL-5 and IL-6 levels, as well as the number of total cells, lymphocytes and eosinophils in bronchoalveolar lavage fluid, (p<0.05). Simultaneously, swimming also increased IL-10 and glutathione levels in the Swimming and OVA+Swimming groups (p<0.05). The levels of glutathione peroxidase and catalase were increased only in the Swimming group when compared to all groups (p<0.05). 21 days of swimming resulted in an attenuation of pulmonary allergic inflammation followed by an increase of glutathione levels in the OVA group. Swimming only increased the levels of glutathione peroxidase and catalase in non-sensitized mice (p<0.05). These data suggest that the pulmonary anti-inflammatory effects produced by 3 weeks of high-intensity swimming in this model of OVA-induced asthma may be, at least partly, modulated by reduced oxidative stress and increased IL-10 production.

Peripheral and spinal activation of cannabinoid receptors by joint mobilization alleviates postoperative pain in mice.

The present study was undertaken to investigate the relative contribution of cannabinoid receptors (CBRs) subtypes and to analyze cannabimimetic mechanisms involved in the inhibition of anandamide (AEA) and 2-arachidonoyl glycerol degradation on the antihyperalgesic effect of ankle joint mobilization (AJM). Mice (25-35g) were subjected to plantar incision (PI) and 24h after surgery animals received the following treatments, AJM for 9min, AEA (10mg/kg, intraperitoneal [i.p.]), WIN 55,212-2 (1.5mg/kg, i.p.), URB937 (0.01-1mg/kg, i.p.; a fatty acid amide hydrolase [FAAH] inhibitor) or JZL184 (0.016-16mg/kg, i.p.; a monoacylglycerol lipase [MAGL] inhibitor). Withdrawal frequency to mechanical stimuli was assessed 24h after PI and at different time intervals after treatments. Receptor specificity was investigated using selective CB1R (AM281) and CB2R (AM630) antagonists. In addition, the effect of the FAAH and MAGL inhibitors on the antihyperalgesic action of AJM was investigated. AJM, AEA, WIN 55,212-2, URB937 and JZL184 decreased mechanical hyperalgesia induced by PI. The antihyperalgesic effect of AJM was reversed by pretreatment with AM281 given by intraperitoneal and intrathecal routes, but not intraplantarly. Additionally, intraperitoneal and intraplantar, but not intrathecal administration of AM630 blocked AJM-induced antihyperalgesia. Interestingly, in mice pretreated with FAAH or the MAGL inhibitor the antihyperalgesic effect of AJM was significantly longer. This article presents data addressing the CBR mechanisms underlying the antihyperalgesic activity of joint mobilization as well as of the endocannabinoid catabolic enzyme inhibitors in the mouse postoperative pain model. Joint mobilization and these enzymes offer potential targets to treat postoperative pain.

High-intensity swimming exercise reduces neuropathic pain in an animal model of complex regional pain syndrome type I: evidence for a role of the adenosinergic system.

This study investigated the involvement of the adenosinergic system in antiallodynia induced by exercise in an animal model of complex regional pain syndrome type I (CRPS-I). Furthermore, we analyzed the role of the opioid receptors on exercise-induced analgesia. Ischemia/reperfusion (IR) mice, nonexercised and exercised, received intraperitoneal injections of caffeine (10mg/kg, a non selective adenosine receptor antagonist), 1,3-dipropyl-8-cyclopentylxanthine (DPCPX) (0.1mg/kg, a selective adenosine A receptor antagonist), ZM241385 (3mg/kg, a selective adenosine A receptor antagonist), adenosine deaminase inhibitor erythro-9-(2-hydroxy-3nonyl) adenine [(EHNA), 5mg/kg, an adenosine deaminase inhibitor] or naloxone (1mg/kg, a nonselective opioid receptor antagonist). The results showed that high-intensity swimming exercise reduced mechanical allodynia in an animal model of CRPS-I in mice. The antiallodynic effect caused by exercise was reversed by pretreatment with caffeine, naloxone, DPCPX but it was not modified by ZM241385 treatment. In addition, treatment with EHNA, which suppresses the breakdown of adenosine to inosine, enhanced the pain-relieving effects of the high-intensity swimming exercise. This is the first report demonstrating that repeated sessions of high-intensity swimming exercise attenuate mechanical allodynia in an animal model of CRPS-I and that the mechanism involves endogenous adenosine and adenosine A receptors. This study supports the use of high-intensity exercise as an adjunct therapy for CRPS-I treatment.

Stretch-induced nerve injury: a proposed technique for the study of nerve regeneration and evaluation of the influence of gabapentin on this model.

The rat models currently employed for studies of nerve regeneration present distinct disadvantages. We propose a new technique of stretch-induced nerve injury, used here to evaluate the influence of gabapentin (GBP) on nerve regeneration. Male Wistar rats (300 g; n=36) underwent surgery and exposure of the median nerve in the right forelimbs, either with or without nerve injury. The technique was performed using distal and proximal clamps separated by a distance of 2 cm and a sliding distance of 3 mm. The nerve was compressed and stretched for 5 s until the bands of Fontana disappeared. The animals were evaluated in relation to functional, biochemical and histological parameters. Stretching of the median nerve led to complete loss of motor function up to 12 days after the lesion (P<0.001), compared to non-injured nerves, as assessed in the grasping test. Grasping force in the nerve-injured animals did not return to control values up to 30 days after surgery (P<0.05). Nerve injury also caused an increase in the time of sensory recovery, as well as in the electrical and mechanical stimulation tests. Treatment of the animals with GBP promoted an improvement in the morphometric analysis of median nerve cross-sections compared with the operated vehicle group, as observed in the area of myelinated fibers or connective tissue (P<0.001), in the density of myelinated fibers/mm2 (P<0.05) and in the degeneration fragments (P<0.01). Stretch-induced nerve injury seems to be a simple and relevant model for evaluating nerve regeneration.

Light-emitting diode therapy induces analgesia and decreases spinal cord and sciatic nerve tumour necrosis factor-α levels after sciatic nerve crush in mice.

BACKGROUND: Neuropathic pain is severely debilitating and resistant to pharmacological approaches; therefore, the study of therapies to complement its treatment is especially relevant. In a case report study, light-emitting diode therapy (LEDT) has shown analgesic activity as well as reduced the expression of pro-inflammatory cytokines in a rabbit osteoarthritis model and in calcaneal tendinitis in rats. Although LEDT stimulated morphofunctional recovery after nerve injury in rats, its effect against neuropathic pain has not been tested. METHODS: To that purpose, mice under anaesthesia were subjected to the sciatic nerve crush (SNC) model. On the seventh post-operative day, after determining analgesic dose (energy density in joules), LEDT (950 nm, 80 mW/cm2, 2.5 J/cm2 ) was irradiated, daily for a period of 15 days, on the skin over the crush site. RESULTS: Compared with the SNC group, LEDT reduced mechanical hypersensitivity but not cold hypersensitivity which is induced by SNC, decreased spinal cord and sciatic nerve levels of tumour necrosis factor alpha (TNF-α) but did not alter interleukin (IL)-1ß and IL-10 levels, and finally, failed to accelerate motor functional recovery and morphological nerve regeneration. CONCLUSION: Taken together, these data provide first-hand evidence of LEDT effectiveness against neuropathic pain induced by SNC, with corresponding decrease of pro-inflammatory cytokine levels, both in the sciatic nerve and in the spinal cord, although at a small analgesic dose, LEDT failed to accelerate nerve regeneration.

Glycogen synthase kinase 3-specific inhibitor AR-A014418 decreases neuropathic pain in mice: evidence for the mechanisms of action.

The present study examined the antihyperalgesic effect of a specific inhibitor of Glycogen Synthase Kinase 3 (GSK3), AR-A014418, on the partial ligation of the sciatic nerve (PSNL), a neuropathic pain model in mice and investigated some mechanisms of action. AR-A014418 (0.01-1 mg/kg) administered by intraperitoneal route (i.p.) inhibited mechanical hyperalgesia. This action started 30 min after i.p. administration and remained significant up to 2 h. When administered daily for 5 days, AR-A014418 (0.3 mg/kg, i.p.) significantly reduced the mechanical hyperalgesia caused by PSNL. Intraperitoneal (i.p.) treatment with AR-A014418 (0.3 mg/kg) also significantly inhibited cold hyperalgesia induced by PSNL. Pre-administration of PCPA (100 mg/kg, i.p., inhibitor of serotonin synthesis) and AMPT (100 mg/kg, i.p., inhibitor of tyrosine hydroxylase), but not l-arginine (600 mg/kg, i.p., a nitric oxide precursor), significantly reduced the mechanical hyperalgesia elicited by AR-A014418. Furthermore, the administration of AR-A014418 significantly prevented the increase of TNF-α (inhibition of 76±8%) and IL-1ß (inhibition of 62±10%), but did not alter lumbar spinal cord IL1-ra and IL-10 levels. Finally, intraperitoneal administration of AR-A014418 did not affect locomotor activity in the open-field test. Taken together, these results provide experimental evidence indicating that AR-A014418 produces marked antihyperalgesic effects in neuropathic pain in mice, possibly due to mechanisms that reduce proinflammatory cytokines, as well as increases in serotonergic and catecholaminergic pathways. The present study suggests that GSK3 may be a novel pharmacological target for the treatment of neuropathic pain and AR-A014418 might be a potential molecule of interest for chronic pain relief.

Neuroprotective and neuroregenerative effects of low-intensity aerobic exercise on sciatic nerve crush injury in mice.

Here, we established a program of low-intensity aerobic exercise and compared the effects of exercise preoperative, postoperative, and a combination of both pre- and postoperative protocols on recovery from sciatic nerve crush injury in mice using behavioral, biochemical, and morphological assays. Sciatic nerve crush was performed in adult male mice. The animals were submitted to preoperative (for 2 weeks), postoperative (for 2 weeks), and a combination of preoperative-postoperative (for 4 weeks) training protocols. During the training period, functional recovery was monitored using the Sciatic Functional Index, the Sciatic Static Index, and mechanical and cold hypersensitivity analyses. Morphological and biochemical alterations were analyzed on the 14th day post-crushing. The functional recovery values of all of the exercised groups were significantly better than the nonexercised group. Biochemically, all of the exercise groups showed a reduction in the increase of interleukin-1ß (IL-1ß) in the sciatic nerve and in the IL-1ß and interleukin-6 receptor (IL-6R) levels in the spinal cord. However, the levels of tumor necrosis factor alpha (TNF-α) decreased only in the postoperative group and in the combination exercise protocols. In the morphological analysis, the combination exercise subjects presented an increase in fiber and axon diameter, in the myelination degree and in the number of myelinated fibers. The present study showed that pre- and postoperative exercise achieved values for functional and morphological sciatic nerve regeneration that were significantly better than either the preoperative or postoperative protocols. This experimental study suggests that physical exercise can restore motor and nerve function to a substantial degree when performed using a prophylactic and therapeutic approach.

(-)-Linalool, a naturally occurring monoterpene compound, impairs memory acquisition in the object recognition task, inhibitory avoidance test and habituation to a novel environment in rats.

It is known that (-)-linalool is a competitive antagonist of NMDA receptors, which play a key role in the learning and memory processes; however, only a few studies have reported a possible interference of (-)-linalool in memory. The purpose of this study was to investigate the (-)-linalool effects on acquisition of short- and long-term memories through the objects recognition task, inhibitory avoidance test and habituation to a novel environment. Furthermore, the open field test was used to investigate the interference of (-)-linalool in motivation, locomotion and exploration by animals. Wistar male adult rats received an intraperitoneal injection (i.p.) of saline (NaCl 0.9%), tween 5% or (-)-linalool (50 or 100 mg/kg) before training in the tasks; MK-801 (0.1 mg/kg), a glutamate antagonist, was used as positive control. Short-term (STM) and long-term (LTM) memories were tested 1.5 and 24 h after training, respectively, in the inhibitory avoidance and recognition objects. The results suggested that (-)-linalool (as 50- and 100-mg/kg doses) impaired LTM acquisition, but not STM acquisition, in the object recognition task. In the inhibitory avoidance test, animals receiving linalool (both doses) showed impairment in acquisition of both memories measured. In the open field test, the animals that received (-)-linalool showed no significant difference in the crossings and latency to start the locomotion in any of the doses tested, although (-)-linalool 100 mg/kg reduced rearing behavior. When re-exposed to open field 24 h after training, the rats that received (-)-linalool 100mg/kg showed no habituation. Taken together, these data suggested that (-)-linalool was able to impair the acquisition of memory in rats, which can be associated to (-)-linalool antagonist capacity as regards NMDA glutamatergic receptors, since other glutamate antagonists also seem to affect memory.

Stretch-induced nerve injury: a proposed technique for the study of nerve regeneration and evaluation of the influence of gabapentin on this model

The rat models currently employed for studies of nerve regeneration present distinct disadvantages. We propose a new technique of stretch-induced nerve injury, used here to evaluate the influence of gabapentin (GBP) on nerve regeneration. Male Wistar rats (300 g; n=36) underwent surgery and exposure of the median nerve in the right forelimbs, either with or without nerve injury. The technique was performed using distal and proximal clamps separated by a distance of 2 cm and a sliding distance of 3 mm. The nerve was compressed and stretched for 5 s until the bands of Fontana disappeared. The animals were evaluated in relation to functional, biochemical and histological parameters. Stretching of the median nerve led to complete loss of motor function up to 12 days after the lesion (P<0.001), compared to non-injured nerves, as assessed in the grasping test. Grasping force in the nerve-injured animals did not return to control values up to 30 days after surgery (P<0.05). Nerve injury also caused an increase in the time of sensory recovery, as well as in the electrical and mechanical stimulation tests. Treatment of the animals with GBP promoted an improvement in the morphometric analysis of median nerve cross-sections compared with the operated vehicle group, as observed in the area of myelinated fibers or connective tissue (P<0.001), in the density of myelinated fibers/mm2 (P<0.05) and in the degeneration fragments (P<0.01). Stretch-induced nerve injury seems to be a simple and relevant model for evaluating nerve regeneration.