Rutin engages opioid/benzodiazepine receptors towards anti-neuropathic potential in a rat model of chronic constriction injury: relevance to its antioxidant and anti-inflammatory effects

Neuropathic pain is a chronic type of pain caused by damage or dysfunction in the nervous system. It can be quite bothersome and often doesn't well respond to common painkillers. Among natural compounds, rutin (Rut) stands out for its remarkable antioxidant, and anti-inflammatory properties. In this research, our objective is to investigate the impact of Rut on an animal model of chronic constriction injury (CCI). A total of 54 adult Wistar rats were divided randomly into nine separate groups. Groups included sham, CCI, gabapentin (GBP, 100 mg/kg), Rut (10, 25 mg/kg), flumazenil (FLU, 0.5 mg/kg), naloxone (NAL, 0.1 mg/kg), Rut (10 mg/kg) + FLU (0.5 mg/kg), and Rut (10 mg/kg) + NAL (0.1 mg/kg). The aforementioned drug injection (intraperitoneal, i.p.) and sensorimotor behavioral tests were performed on days 1, 3, 5, 7, 9, 11, and 14. Biochemical (e.g., nitrite, catalase, glutathione), zymography (matrix-metalloproteinase 2 and 9), and histopathological tests were performed on day 14 after surgery. The findings demonstrated that Rut administration effectively alleviated symptoms of allodynia/hyperalgesia, and improved locomotor activity following CCI. Additionally, Rut administration resulted in increased catalase and glutathione activity, while reducing serum nitrite levels, as well as matrix metalloproteinase 2 and 9 activity. Additionally, histological results indicated that Rut improved sciatic nerve regeneration. Since the aforementioned effects of Rut were reversed by using opioid and benzodiazepine receptor antagonists (i.e., NAL and FLU, respectively), the receptors' involvement was revealed in the anti-neuropathic effects of Rut. In conclusion, Rut emerged as a potentially effective candidate for treating neuropathic pain and improving motor function by increasing antioxidant mediators, suppressing inflammation, and activating opioid/benzodiazepine receptors.

The effect of risperidone on behavioral reactions and gene expression of pro- and anti-inflammatory cytokines in neuropathic pain model induced by chronic constriction injury of the sciatic nerve in rat

BACKGROUND

Neuropathic pain results from lesions or diseases affecting the somatosensory system. The management of a patient with chronic neuropathic pain remains a challenge several studies report the analgesic effect of serotonin receptor antagonists in different models of experimental pain. The present study was designed to study the effect of systemic administration of risperidone, on behavioral scores of neuropathic pains in chronic constriction (CCI) model in rats.

METHODS

Inducing neuropathic pain with the CCI model which causes heat hyperalgesia, heat, and mechanical allodynia was performed on rats, and then, in two phases, risperidone effect was determined. In the acute phase, risperidone 1, 2, 4 mg was administered for three groups half an hour before behavioral tests on the 7th, 14th, and 21st day after surgery, and in the chronic phase, risperidone 1, 2, and 4 mg was administered for three different groups from the 1st to 14th days after surgery than on 14th-day behavioral scores were performed. For gene expression analysis, samples are taken from spinal cord tissues in lumbar segments.

RESULTS

This study shows chronic administration of risperidone as an antipsychotic drug was effective on heat hyperalgesia and allodynia. However, only the max dosage (4 mg) of risperidone showed meaningful improvement in increasing mechanical allodynia. However, acute administering of risperidone did not show any meaningful changes in behavioral tests on neuropathic pain induced by chronic constriction injury of the sciatic nerve in rats. In addition, gene expression results showed an increase in IL-4 and IL-10 gene expression in the risperidone group compared to the sham group.

CONCLUSION

This study suggests the helpful preventive effects of risperidone in developing and increasing neuropathic pain, but it does not have any instant effect.

Long-standing groin pain syndrome in athletic women: a multidisciplinary assessment in keeping with the italian consensus agreement

BACKGROUND

Long-standing groin pain syndrome (LSGPS) is a form of groin pain syndrome in which the cohort of symptoms reported by patients is experienced for a long period, typically for over 12 weeks, and is recalcitrant to any conservative therapy. The aim of this prospective epidemiological study was to describe the clinical causes of LSGPS in 37 female athletic subjects in Italy through the Groin Pain Syndrome Italian Consensus Conference on terminology, clinical evaluation and imaging assessment in groin pain in athletes classification and guidelines.

METHODS

Thirty-seven female athletes affected by LSGPS were evaluated following the guidelines issued by the Groin Pain Syndrome Italian Consensus Conference on terminology, clinical evaluation and imaging assessment of groin pain in athletes.

RESULTS

In the considered population, each patient presented only one pathological cause for LSGPS. The most frequent aetiologies were inguinal pathologies (54.05% of the cases), acetabular labrum tear (18.92%) and pelvic floor disorders (8.11%). Adductor tendinopathy represented only 2.70% of cases.

CONCLUSIONS

Female athletic patients affected by LSGPS show a similar incidence of inguinal and hip pathologies as in male populations. However, these clinical situations do not seem to be associated in women unlike in the male population. This difference is probably due to particular anatomical differences related to gender. For this reason, women affected by LSGPS represent an important subset of patients. Moreover, adductor tendinopathy is probably overrated as an etiopathogenetic source of LSGPS in women.

Pulsed magnetic field enhances therapeutic efficiency of mesenchymal stem cells in chronic neuropathic pain model

Cell-based or magnetic field therapies as alternative approaches to pain management have been tested in several experimental pain models. The aim of this study therefore was to investigate the actions of the cell-based therapy (adipose tissue derived mesenchymal stem cells; ADMSC) or pulsed magnetic field (PMF) therapy and magneto-cell therapy (combination of ADMSC and PMF) in chronic constriction nerve injury model (CCI). The actions of individual ADMSC (route dependent [systemic or local], time-dependent [a day or a week after surgery]), or PMF and their combination (magneto-cell) therapies on hyperalgesia and allodynia were investigated by using thermal plantar test and a dynamic plantar aesthesiometer, respectively. In addition, various cytokine levels (IL-1β, IL-6, and IL-10) of rat sciatic nerve after CCI were analyzed. Following the CCI, both latency and threshold significantly decreased. ADMSC or PMF significantly increased latencies and thresholds. The combination of ADMSC with PMF even more significantly increased latency and threshold when compared with ADMSC alone. However, ADMSC-induced decrease in pro-inflammatory or increase in anti-inflammatory cytokines levels were partially prevented by PMF treatments. Present findings may suggest that both cell-based and magnetic therapies can effectively attenuate chronic neuropathic pain symptoms. Combined magneto-cell therapy may also efficiently reverse neuropathic signs. Bioelectromagnetics. 38:255-264, 2017. © 2017 Wiley Periodicals, Inc.

Antinociceptive activity of the selective iNOS inhibitor AR-C102222 in rodent models of inflammatory, neuropathic and post-operative pain

Nitric oxide generated by the nitric oxide synthase (NOS) isoforms contributes to pain processing. The selective inhibition of iNOS might represent a novel, therapeutic target for the development of antinociceptive compounds. However, few isoform-selective inhibitors of NOS have been developed. The present experiments examined the anti-inflammatory and antinociceptive activity of a selective inducible nitric oxide (iNOS) inhibitor, AR-C102222, on arachidonic acid-induced ear inflammation, Freund's complete adjuvant (FCA)-induced hyperalgesia, acetic acid-induced writhing, and tactile allodynia produced by L5 spinal nerve ligation (L5 SNL) or hindpaw incision (INC). AR-C102222 at a dose of 100mg/kg p.o., significantly reduced inflammation produced by the application of arachidonic acid to the ear, attenuated FCA-induced mechanical hyperalgesia, and attenuated acetic acid-induced writhing. In the L5 SNL and INC surgical procedures, tactile allodynia produced by both procedures was significantly reduced by 30mg/kg i.p. of AR-C102222. These data demonstrate that the selective inhibition of iNOS produces antinociception in different models of pain and suggest that the iNOS-NO system plays a role in pain processing.

[New, relevant and practical aspects of the treatment of neuropathic pain]

In the Spanish population it is difficult to calculate the prevalence of neuropathic pain (NP) although it is estimated that it is present in 40% of the cases of chronic pain. The treatment is not easy and we must choose between the different drugs, the most appropriate taking into account the effectivity in data from clinical trials, releaf of comorbidities associated to NP and less side effects. In this way, the Finnerup NB's work establishes an algorithm of treatment of NP and it is very helpful for clinicians in order to choose the most suitable treatment. In this work, the author recommends antiepileptic drugs, like gabapentin and pregabalin as first choice treatments. Amitriptiline, a tricycle antidepressant and opioids must be used only when there is a lack of response or intolerance.

Pharmacotherapy for Neuropathic Pain

Refractory neuropathic pain can be devastating to a patient's quality of life. Ideally, the primary goal of therapy would be to prevent the pain, yet even the most appropriate treatment strategy may be only able to reduce the pain to a more tolerable level. Pharmacotherapy is currently the mainstay of treatment in patients with neuropathic pain, although at present the drugs are used on a mainly "off-label" basis. A wide variety of agents are used, especially antidepressants (ie, tricyclic antidepressants, selective serotonin-reuptake inhibitors) and anticonvulsants, but also opioids and tramadol, topical agents (eg, lidocaine), systemic local anesthetics, and anti-inflammatories. Even so, effective pain relief is achieved in less than half of patients with chronic neuropathic pain. In refractory patients, combination therapy using two agents with synergistic mechanisms of action may offer greater pain relief without compromising the side-effect profile of each agent.

Pharmacological evaluation of the selective spinal nerve ligation model of neuropathic pain in the rat

Rodent models of neuropathic pain are used to investigate the underlying mechanisms of pain associated with damage to peripheral nerves and to evaluate the efficacy of novel compounds. However, few models have been adequately characterized and the validity of many models remains unclear. The present experiment examined the activity of known anti-allodynic compounds in the L5 spinal nerve ligation (SNL) model of peripheral mononeuropathy in the rat, a modified version of the L5/L6 SNL model [S.H. Kim, J.M. Chung, An experimental model for peripheral neuropathy produced by segmental spinal nerve ligation in the rat, Pain 50 (1992) 355-363]. Tactile sensitivity was measured 7-21 days post-surgery using von Frey monofilaments before and following treatment with gabapentin (30, 60 and 120 mg/kg), morphine (1, 3 and 6 mg/kg), amitriptyline (1.5, 3 and 10 mg/kg), fluoxetine (3, 10 and 30 mg/kg), WIN55,212-2 (0.5, 1 and 2.5 mg/kg), indomethacin (1 and 5 mg/kg) or U-50,488H (3 and 6 mg/kg). Compared to sham-operated control animals, L5 SNL animals displayed significant tactile allodynia in the ipsilateral hindpaw that was completely reversed by treatment with gabapentin, morphine, and WIN55,212-2, partially reversed by amitriptyline and fluoxetine, and unaffected by U-50,488H or indomethacin. The robust effects of the non-selective cannabinoid receptor agonist WIN55,212-2 and morphine support reports in the literature that systemic cannabinoid receptor agonists and opioids are active in neuropathic pain. These results suggest that the L5 SNL model can be utilized to determine the anti-allodynic activity of novel compounds.

Decreased L5 spinal nerve ligation nociceptive behavior following L4 spinal nerve transection

This study used the escape/avoidance paradigm to explore the role of the L4 spinal nerve in L5 ligation nociception. Unlike L5-ligated controls, L5-ligated/L4-transected animals had normal mechanical withdrawal threshold and did not escape/avoid mechanical stimulation of the afflicted paw. The result from the escape/avoidance paradigm, which does not rely on a reflexive withdrawal response, directly supports the hypothesis that the L4 spinal nerve contributes to L5 ligation neuropathic pain.