Antinociceptive Effect of Memantine and Morphine on Vincristine-induced Peripheral Neuropathy in Rats

Animal models of chemotherapy-induced peripheral neuropathy for hematological malignancies: A review

Chemotherapy is one of the main treatments for hematologic malignancies. However, chemotherapy-induced peripheral neuropathy (CIPN) is one of the most common long-term toxic reactions in chemotherapy, and the occurrence of CIPN affects patients' quality of life and can cause interruption of chemotherapy in severe cases, thus reducing the efficacy of chemotherapy. We currently summarize the existing CIPN animal models, including the characteristics of several common animal models such as bortezomib-induced peripheral neuropathy, vincristine-induced peripheral neuropathy, and oxaliplatin-induced peripheral neuropathy. It was found that CIPN may lead to behavioral, histopathological, and neurophysiological changes inducing peripheral neuropathy. However, the mechanism of CIPN has not been fully elucidated, especially the prevention and treatment protocols need to be improved. Therefore, this review article summarizes the progress of research on CIPN animal models and the possible mechanisms and treatment of CIPN.

Mechanistic efficacy assessment of selected novel methanimine derivatives against vincristine induced Neuropathy: In-vivo, Ex-vivo and In-silico correlates

Vincristine induced peripheral neuropathy (VIPN) is a serious untoward side effect suffered by cancer patients, which still lacks an adequate therapeutic approach. This study examined the alleviating potential of novel methanimine derivatives i.e. (E)-N-(4-nitrobenzylidene)-4-chloro-2-iodobenzamine (KB 9) and (E)-N-(2-methylbenzylidene)-4-chloro-2-iodobenzamine (KB 10) in VIPN. Vincristine was injected in BALB/c mice for 10 days to instigate nociceptive neuropathy. Dynamic and static allodynia, thermal (hot and cold) hyperalgesia were evaluated at 0, 5, 10 and 14 days using cotton brush, Von Frey filament application, hot plate test, acetone drop and cold water respectively. Tumour necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), lipid peroxide (LPO), glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD) and reactive oxygen species (ROS) assays were performed to assess the efficacy of KB9 and KB10 against neuroinflammation and oxidative stress utilizing ELISA, immunohistochemistry and western blot analysis in brain and sciatic nerve tissues. Computational studies were executed to determine the stable binding conformation of both compounds with respect to COX-2 and NF-κB. Interestingly, both compounds substantially reduced protein expression related to neuroinflammation, oxidative stress (LPO, GST, SOD, CAT) and pain (NF-κB, COX-2, IL-1β and TNF-α). This molecular analysis suggested that the neuroprotective effect of KB9 and KB10 was mediated via regulation of inflammatory signaling pathways. Overall, this study demonstrated that KB9 and KB10 ameliorated vincristine induced neuropathy, through anti-inflammatory, anti-nociceptive and antioxidant mechanisms.

Expression Profiling of L5-S2 Spinal Cord Dorsal Horn in a Rat Model of Chronic Pelvic Pain Syndrome Uncovers Potential Mechanism of Electroacupuncture Mediated Inflammation and Pain Responses

Purpose

We aim to explore expression profiles of genes in SCDH of CPPS model rat relevant to pain and inflammation by RNA-Seq and to investigate the mechanism of anti-inflammatory and analgesic of EA.

Methods

Thirty-six SD male rats were randomly divided into three groups (n = 12): sham operation, model, and EA. The rat CPPS model was established by injecting CFA into the ventral lobes of the prostate. The rats in EA group were treated at Guanyuan (CV4), Zhongji (CV3), Sanyinjiao (SP6) and Huiyang (BL35) for a total of 20 times, with a frequency of 2/100Hz. Mechanical allodynia, H&E staining and ELISA were used to detect the changes of pain threshold and tissue inflammation; RNA-Seq technique was used for profiling gene changes in SCDH and qRT-PCR was used for further validation.

Results

Persistent mechanical allodynia and severe tissue inflammatory reaction both occurred in CPPS rats. After EA therapy, the pain sensitivity and inflammatory response of CPPS rats decreased significantly. RNA-Seq identified that a total of 46 DEGs were significantly up-regulated and 65 DEGs down-regulated after EA. GO enrichment showed that EA was mainly reflected in the regulation of the immune system by participating in the regulation of leukocyte, neutrophil cellular processes and cytokine metabolism. KEGG enrichment demonstrated that signal transduction and immune system were the most significant pathways. We further identified that the expressions of Pik3r2, Akt1, and Casp9 were significantly up-regulated and Jak2 and Stat3 down-regulated in the PI3K-AKT/JAK-STAT signal pathway.

Conclusion

Our study revealed that immune and inflammatory responses are the main biological events that induce chronic pelvic pain in rats, and EA can exert anti-inflammatory and analgesic effects by regulating the expression of related genes on PI3K-AKT/JAK-STAT signal pathway in SCDH. This study provided putative novel targets of EA, which may have anti-inflammatory and analgesic effects of CPPS.

Memantine and its benefits for cancer, cardiovascular and neurological disorders

Memantine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist that was initially indicated for the treatment of moderate to severe Alzheimer's disease. It is now also considered for a variety of other pathologies in which activation of NMDA receptors apparently contributes to the pathogenesis and progression of disease. In addition to the central nervous system (CNS), NMDA receptors can be found in non-neuronal cells and tissues that recently have become an interesting research focus. Some studies have shown that glutamate signaling plays a role in cell transformation and cancer progression. In addition, these receptors may play a role in cardiovascular disorders. In this review, we focus on the most recent findings for memantine with respect to its pharmacological effects in a range of diseases, including inflammatory disorders, cardiovascular diseases, cancer, neuropathy, as well as retinopathy.

Chemotherapy-Induced Peripheral Neuropathy: Mechanisms and Therapeutic Avenues

Chemotherapy-induced peripheral neuropathy (CIPN) is a serious and often persistent adverse consequence of certain chemotherapeutic agents. It is a major dose-limiting factor of many first-line chemotherapies, affecting 20-50% of patients at standard doses and nearly all patients at high doses. As cancer survivorship continues to increase with improvements in early diagnosis and treatment, more patients will experience CIPN despite completing cancer treatment, which interferes with recovery, leading to chronic pain and worsening quality of life. The National Cancer Institute has identified CIPN as a priority in translational research. To date, there are no FDA-approved drugs for preventing or treating CIPN, with emerging debate on mechanisms and promising new targets. This review highlights current literature and suggests novel approaches to CIPN based on proposed mechanisms of action that aim either to confer neuroprotection against chemotherapy-induced neurotoxicity or reverse the downstream effects of painful neuropathy.

Comparison of chemotherapy effects on mechanical sensitivity and food-maintained operant responding in male and female rats

Chemotherapies of varying classes often cause neuropathy and debilitating chemotherapy-induced neuropathic pain sufficient to limit treatment and reduce quality of life for many patients battling cancer. There are currently no effective preventive or alleviative treatments for chemotherapy-induced neuropathic pain. Preclinical models have been developed to test candidate chemotherapy-induced neuropathic pain treatments; however, studies using these models rarely provide direct comparisons of effects of different chemotherapies or assess the degree to which chemotherapies produce clinically relevant signs of pain-depressed behavior. Male and female Sprague-Dawley rats received four injections of vehicle, paclitaxel, oxaliplatin, vincristine, or bortezomib on alternate days. Mechanical hypersensitivity, body weight, and food-maintained operant responding were evaluated before, during, and for up to 42 days after initiation of treatment. Morphine potency and effectiveness to reverse chemotherapy-induced effects were also evaluated. All four chemotherapies produced dose-dependent and sustained mechanical hypersensitivity in all rats. Vincristine and oxaliplatin produced transient weight loss and decreases in food-maintained operant responding in all rats, whereas paclitaxel and bortezomib produced lesser or no effect. At 4 weeks after treatment, operant responding was depressed only in paclitaxel-treated males. Morphine reversed mechanical hypersensitivity in all rats but failed to reverse paclitaxel-induced depression of operant responding in males. We conclude that chemotherapy treatments sufficient to produce sustained mechanical hypersensitivity failed to produce sustained or morphine-reversible behavioral depression in rats. Insofar as pain-related behavioral depression is a cardinal sign of chemotherapy-induced neuropathic pain in humans, these results challenge the presumption that these chemotherapy-dosing regimens are sufficient to model clinically relevant chemotherapy-induced neuropathic pain in rats.

Analgesic Efficacy of Nefopam as an Adjuvant in Patient-Controlled Analgesia for Acute Postoperative Pain After Laparoscopic Colorectal Cancer Surgery

Despite rapid advancements in laparoscopic surgical techniques and perioperative management, postoperative pain remains a significant clinical issue. We examined the analgesic efficacy of nefopam as an adjuvant in patient-controlled analgesia (PCA) for acute postoperative pain in patients undergoing laparoscopic colorectal cancer surgery. We retrospectively analyzed the medical records of 120 patients who did or did not receive 80 mg of nefopam as an adjuvant in fentanyl PCA; they were allocated to the nefopam (n = 60) or non-nefopam group (n = 60). The demographic, clinical, and anesthetic data, with data on pain severity and opioid administration at the postoperative anesthesia care unit (PACU) on postoperative days (PODs) 1, 3, and 5, were compared between the groups. The pain score and opioid administration did not differ at the PACU or on PODs 1, 3, or 5. The day of PCA discontinuation, time to pass flatus, length of the hospital stay, and incidence of nausea/vomiting, dizziness, and headache also did not differ between the groups. Fentanyl PCA with 80 mg of nefopam as an adjuvant did not have a superior analgesic effect after laparoscopic colorectal cancer surgery.

Protective effect of gastrodin on peripheral neuropathy induced by anti-tumor treatment with vincristine in rat models

Cancer is a common disease threatening human health, chemotherapy is widely used in clinical treatment of cancer, but chemotherapy-induced peripheral neuropathy (CIPN) has a relevant impact on life quality of cancer patients. Administration of gastrodin can relieve chronic pain to cancer patients with CIPN and attenuated the inflammatory response by reducing the expression of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). However, its exact molecular mechanisms remain unclear. In this study, we established an animal model of CIPN using Walker-256 breast cancer cell and vincristine. We found that the mechanical and thermal pain threshold of rats was decreased with treatment of vincristine. Using gastrodin could restore the mechanical and thermal threshold without interfering anti-tumor effect of vincristine. Gastrodin relieved CIPN by inhibiting activation of spinal microglia through Fractalkine (CX3CL1) and its receptor CX3CR1, then inhibited P38/mitogen-activated protein kinase (MAPK) signaling pathway and reduced the expression of inflammatory factor TNF-α and interleukin-1β (IL-1β). Taking together, our study demonstrated that gastrodin is a potential drug for the treatment of CIPN and likely to improve cancer patient's life quality.

Emerging pharmacological strategies for the management of chemotherapy-induced peripheral neurotoxicity (CIPN), based on novel CIPN mechanisms

INTRODUCTION

Based on results of available clinical trials, the treatment and prevention of chemotherapy-induced peripheral neurotoxicity (CIPN) largely remains an unmet clinical need. However, new approaches have emerged in the last few years, attempting to modify the natural history of acute and late CIPN effects through a better knowledge of the pathogenic process on the molecular level.

AREAS COVERED

Clinical results of recently published (last 5 years) or ongoing emerging therapeutic/preventive pharmacological approaches based on novel CIPN mechanisms have been identified from Pubmed and ClinicalTrials.gov. Results are reviewed and discussed, in order to assess the trend of new clinical studies but also to infer the role novel approaches may have in the future.

EXPERT OPINION

The large heterogeneity of disease-causing mechanisms prevents researchers from identifying a reliable approach to effectively and safely treat or prevent CIPN. Understanding of novel pathophysiologic processes is leading the way to novel therapies, which, through targeting the sphingosine 1-phosphate receptor or pharmacologically inhibiting axonal degeneration might achieve in the future both treatment and prevention of CIPN. Toward this end, a multi-targeting approach, combining drugs to target different CIPN pathomechanisms seems to be a rational approach that warrants testing.

The Antiallodynic Effect of Nefopam on Vincristine-Induced Neuropathy in Mice

Background

Chemotherapy-induced neuropathic pain is a disabling condition following cancer treatment. Vincristine has more neurotoxicity than other vinca alkaloid agents. This study evaluated the correlation of different doses of nefopam with antiallodynic effects in a mouse vincristine neuropathy model.

Methods

A peripheral neuropathic mouse model was made by intraperitoneal injection of vincristine (0.1 mg/kg/day; 5-day-on, 2-day-off schedule over 12 days). After the development of allodynia, mice were injected intraperitoneally with 0.9% normal saline (NS group) or various doses (10, 30, 60 mg/kg) of nefopam (Nefopam group). We examined allodynia using von Frey hairs pre-administration and at 30, 60, 90, 120, 180, 240 mins, and 24 hrs after drug administration. We also measured the neurokinin-1 receptor concentrations in the spinal cord to confirm the antiallodynic effect of nefopam after drug administration.

Results

The peripheral neuropathic mouse model showed prominent mechanical allodynia. Intraperitoneal nefopam produced a clear dose-dependent increase in paw withdrawal threshold compared with pre-administration values and versus the NS group. The concentration of neurokinin-1 receptor was significantly decreased in the Nefopam group (P<0.05).

Conclusion

Intraperitoneally administered nefopam yielded a dose-dependent attenuation of mechanical allodynia and decreased neurokinin-1 receptor concentration, suggesting that the neurokinin-1 receptor is involved in the antiallodynic effects of nefopam in vincristine neuropathy.

The effect of analgesics on stimulus evoked pain-like behaviour in animal models for chemotherapy induced peripheral neuropathy- a meta-analysis

Chemotherapy induced painful peripheral neuropathy (CIPN) is a common dose-limiting side effect of several chemotherapeutic agents. Despite large amounts of human and animal studies, there is no sufficiently effective pharmacological treatment for CIPN. Although reducing pain is often a focus of CIPN treatment, remarkably few analgesics have been tested for this indication in clinical trials. We conducted a systematic review and meta-analyses regarding the effects of analgesics on stimulus evoked pain-like behaviour during CIPN in animal models. This will form a scientific basis for the development of prospective human clinical trials. A comprehensive search identified forty-six studies. Risk of bias (RoB) analyses revealed that the design and conduct of the included experiments were poorly reported, and therefore RoB was unclear in most studies. Meta-analyses showed that administration of analgesics significantly increases pain threshold for mechanical (SMD: 1.68 [1.41; 1.82]) and cold (SMD: 1. 41 [0.99; 1.83]) evoked pain. Subgroup analyses revealed that dexmedetomidine, celecoxib, fentanyl, morphine, oxycodone and tramadol increased the pain threshold for mechanically evoked pain, and lidocaine and morphine for cold evoked pain. Altogether, this meta-analysis shows that there is ground to investigate the use of morphine in clinical trials. Lidocaine, dexmedetomidine, celecoxib, fentanyl, oxycodone and tramadol might be good alternatives, but more animal-based research is necessary.

Notch activation enhances microglial CX3CR1/P38 MAPK pathway in rats model of vincristine-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) has a adverse impact to the living quality of cancer patients. This side effect of CIPN limit the dose of drug used in many chemotherapies, such as vincristine (VCR). The activation of microglia in the spinal dorsal horn is involved in the occurrence and development of neuropathic pain induced by VCR. Recent study has demonstrated that hypoxia induced microglia activation depends on Notch signaling, and it is involved in the release of many inflammatory related factors in microglia. In this work, we aimed to study that the role of Notch signaling pathway in microglia activation on a VCR-induced neuropathy rat model. Our results showed that the mechanical, thermal and cold pain threshold of rats was decreased by treatment of VCR, but N-[N-(3,5-difluorophenacetyl)-l-alanyl]-S-phenylglycine t-butyl ester (DAPT), a γ-secretase inhibitor, relieved the hyperalgesia. Molecular analysis showed that activation of Notch signaling pathway increased after nerve injury and that DAPT could significantly inhibit the upregulation of Notch signaling pathway, the activation of microglia, and the release of pro-inflammatory cytokines in the spinal. Taking together, Notch signaling pathway could be a potential therapeutic target to alleviate neuropathic pain.

Neuropharmacological Properties of the Essential Oil of Bergamot for the Clinical Management of Pain-Related BPSDs

BACKGROUND

Alzheimer's Disease (AD) accounts for approximately 50% of all cases of dementia and, in spite of the great effort for the development of disease-modifying drugs, a definitive treatment of cognitive impairment is not available yet. A perfect adherence to the current therapy of cognitive decline is needed for a better control of the disease and this is proven to reduce, though not completely abolish, the associated Behavioural and Psychological Symptoms of Dementia (BPSDs) from occurring. This cluster of symptoms, remarkably affecting patients' health-related quality of life (HRQL), is tightly associated with pain states. Antipsychotics are the only treatment for BPSDs. However, these drugs are more effective and safer in the short-term (6-12 weeks), they are able to manage aggression but not agitation and they cannot control pain. Aromatherapy with Melissa officinalis and Lavandula officinalis has been employed to handle BPSDs, but it has not provided strong evidence to offer relief from pain.

OBJECTIVE

Bergamot Essential Oil (BEO) exerts antinociceptive activity through several pharmacological mechanisms: in particular, it is able to enhance autophagy, a process undergoing derangement in chronic pain. Thus, the sound pharmacological basis for clinical translation of aromatherapy with BEO in the treatment of BPSDs has been pointed out.

CONCLUSION

The antinociceptive effects elicited by BEO in experimental pain models make it a possible candidate for the pharmacological management of pain-related BPSDs.

High-Intensity Ultrasound Treatment for Vincristine-Induced Neuropathic Pain

BACKGROUND

Vincristine is a commonly used chemotherapeutic agent that results in debilitating untreatable peripheral neuropathy.

OBJECTIVE

To determine the effects of pulsed high-intensity focused ultrasound (HIFU) on sensory thresholds in a validated vincristine-induced neuropathy (VIN) rodent model.

METHODS

VIN was induced and mechanical allodynia was confirmed by nociceptive testing. von Frey fibers and Randall-Sellito test were used as measures of innocuous and noxious mechanical thresholds, respectively, and the hot plate test for thermal thresholds. Tests were performed before VIN, after 2 wk of vincristine, at 24, 48, 72, and 120 h after HIFU applied to the left L5 dorsal root ganglia at 3 Watts for 3 min. Comparisons were made between a VIN cohort who underwent HIFU, a VIN cohort who underwent sham HIFU, and naïve rodents who underwent HIFU.

RESULTS

VIN HIFU rats had significantly increased mechanical thresholds at 24 h (P &lt; .001), 48 h (P = .008), 72 h (P = .003), and 120 h (P = .03) after treatment, when compared to pre-HIFU thresholds. Furthermore, at 24 and 48 h following treatment, VIN HIFU rats had significantly higher innocuous and noxious mechanical thresholds and thermal thresholds than VIN sham HIFU rats (P &lt; .001). Thresholds were not altered in naïve rodents who underwent HIFU. Histological data of L5 dorsal root ganglia of VIN HIFU rats suggest that transient cellular edema resolves by 48 h.

CONCLUSION

Our data suggest that HIFU increases mechanical and thermal thresholds in VIN rodents. Whether HIFU can preclude the development of reduced thresholds in the VIN model warrants further study.

Optimization and pharmacological characterization of a refined cisplatin-induced rat model of peripheral neuropathic pain

Chemotherapy-induced peripheral neuropathy (CIPN) is the major dose-limiting side-effect of many front-line anticancer drugs. This study was designed to establish and pharmacologically characterize a refined rat model of cisplatin-induced CIPN. Adult male Sprague-Dawley rats received four (n=18) or five (n=18) single intraperitoneal bolus doses of cisplatin at 3 mg/kg, or saline (control group), once-weekly. Body weight and general health were assessed over a 49-day study period. von Frey filaments and the Hargreaves test were used to define the time course for the development of mechanical allodynia and thermal hypoalgesia in the hindpaws and for efficacy assessment of analgesic/adjuvant agents. The general health of rats administered four cisplatin doses was superior to that of rats administered five doses. Mechanical allodynia was fully developed (paw withdrawal thresholds≤6 g) in the bilateral hindpaws from day 32 to 49 for both cisplatin dosing regimens. They also showed significant thermal hypoalgesia in the bilateral hindpaws. In cisplatin-treated rats with paw withdrawal thresholds of up to 6 g, single bolus doses of gabapentin and morphine produced dose-dependent analgesia, whereas meloxicam and amitriptyline lacked efficacy. We have established and pharmacologically characterized a refined rat model of CIPN that is suitable for efficacy profiling of compounds from analgesic discovery programmes.

The effect of thioctic acid on allodynia in a rat vincristine-induced neuropathy model

Objective

To investigate the antiallodynic effects of thioctic acid in vincristine-induced neuropathy in rats.

Methods

Neuropathy was induced in Sprague–Dawley rats via vincristine intraperitoneal injection. After 15 days, rats were investigated for the presence of mechanical and cold allodynia, and those with allodynia received intraperitoneal injection with normal saline or 1, 5, or 10 mg/kg thioctic acid. Mechanical and cold allodynia were assessed before treatment and at 15, 30, 60, 90, 150 and 180 min after treatment.

Results

Mechanical and cold allodynia were reduced by thioctic acid injection. The duration of effect increased with thioctic acid dose.

Conclusion

Thioctic acid may be an effective treatment for vincristine-induced neuropathy.

Antinociceptive effect of matrine on vincristine-induced neuropathic pain model in mice

Chemotherapy drugs treatment causes neuropathic pain, hyperalgesia and allodynia are common components of neuropathic pain, so effectively therapeutic strategy is required. In this study, we evaluated the antinociceptive effects of matrine on vincristine-induced neuropathic pain in mice. Vincristine (100 μg/kg i.p.) was administered once per day for 7 days (day 0-6) in mice. Matrine (15, 30, 60 mg/kg, i.p.) was repeated administration in early phase (day 0-6) or late phase (day 7-13). Hyperalgesia and allodynia were evaluated by withdrawal response using von Frey filaments, plantar and cold-plate on 7, 14 and 21 day. Injection of vincristine produced mechanical hyperalgesia and cold allodynia. Matrine was found to produce a protective role in both von Frey filaments and cold-plate test. The analysis of the effect supports the hypothesis that matrine is useful in therapy of vincristine-induced neuropathic pain. In conclusion, this study demonstrates that administration of matrine is associated with antinociceptive effect on mechanical and cold stimuli in a mice model of vincristine-induced neuropathy pain.

Analgesic effects of dexmedetomidine in vincristine-evoked painful neuropathic rats

Dexmedetomidine, which is a selective α2-adrenoceptor agonist, was recently introduced into clinical practice for its analgesic properties. The purpose of this study was to evaluate the effects of dexmedetomidine in a vincristine-evoked neuropathic rat models. Sprague-Dawley rats were injected intraperitoneally with vincristine or saline (0.1 mg/kg/day) using a 5-day-on, 2-day-off schedule for 2 weeks. Saline and dexmedetomidine (12.5, 25, 50, and 100 µg/kg) were injected to rats developed allodynia 14 days after vincristine injection, respectively. We evaluated allodynia at before, 15, 30, 60, 90, 120, 180, and 240 min, and 24 hr after intraperitoneal drug (normal saline or dexmedetomidine) injection. Saline treatment did not show any differences for all the allodynia. Maximal paw withdrawal thresholds to mechanical stimuli were 3.0 ± 0.4, 9.1 ± 1.9, 13.0 ± 3.6, 16.6 ± 2.4, and 24.4 ± 1.6 g at saline, 12.5, 25, 50, and 100 µg/kg dexmedetomidine injection, respectively. Minimal withdrawal frequency to cold stimuli were 73.3 ± 4.2, 57.1 ± 6.8, 34.3 ± 5.7, 20.0 ± 6.2, and 14.3 ± 9.5 g at saline, 12.5, 25, 50, and 100 µg/kg dexmedetomidine injection, respectively. Dexmedetomidine shows a dose-dependent antiallodynic effect on mechanical and cold stimuli in vincristine-evoked neuropathic rat models (P < 0.05).

Ameliorative effect of Vernonia cinerea in vincristine-induced painful neuropathy in rats

The present study was designed to investigate the antinociceptive potential of Vernonia cinerea (VC) on vincristine-induced painful neuropathy in rats. A chemotherapeutic agent, vincristine (50 μg/kg intraperitoneally for 10 consecutive days), was administered for the induction of neuropathic pain in rats. The painful behavioral changes were assessed using hot plate, acetone drop, paw pressure, Von Frey hair and tail immersion tests to assess the degree of hyperalgesic and allodynic pain sensation in paw and tail. Tissue biomarker changes including  thiobarbituric acid reactive substances (TBARSs), reduced glutathione (GSH) and total calcium levels were estimated in sciatic nerve tissue samples to assess the degree of oxidative stress. Histopathological changes were also observed in transverse sections of rat sciatic nerve tissue. Ethanolic extract of VC leaves and pregabalin were administered for 14 consecutive days from day 0 (day of surgery). Pregabalin served as a positive control in the present study. Vincristine administration resulted in a significant reduction in painful behavioral changes along with a rise in the levels of TBARS, total calcium and decrease in GSH levels when compared with the normal control group. Furthermore, significant histopathological changes were also observed. Pretreatment with VC significantly attenuated vincristine-induced development of painful behavioral, biochemical and histological changes in a dose-dependent manner, which is similar to that of pregabalin-pretreated group. The attenuating effect of VC in vincristine-induced nociceptive painful sensation may be due to its potential of antioxidative, neuroprotective and calcium channel inhibitory action.

Ginkgo biloba extract attenuates hyperalgesia in a rat model of vincristine-induced peripheral neuropathy

BACKGROUND

Chemotherapy-induced peripheral neuropathy is a common, dose-limiting side effect of cancer chemotherapeutic drugs. Hyperalgesia is a common component of neuropathic pain. Ginkgo biloba extract (GBE) is an oriental herbal medicine that has various pharmacological actions. In this study, we evaluated the effects of oral GBE on hyperalgesia in a rat model of vincristine-induced neuropathy.

METHODS

Male Sprague-Dawley rats (200-250 g) were injected intraperitoneally with vincristine or saline (0.1 mg/kg/d) using a 5-day-on, 2-day-off schedule over 12 days. All the behavioral tests for mechanical, cold, and heat hyperalgesia were conducted before the daily injection during the course of vincristine treatment. Rats that developed hyperalgesia 14 days after vincristine injection were randomly assigned into 4 groups. Distilled water and GBE (50, 100, and 150 mg/kg) were administered, respectively, to the individual groups. We examined the hyperalgesia at preadministration and at 15, 30, 60, 90, 120, 150, and 180 minutes after oral drug administration.

RESULTS

Saline injection did not have any significant effect on mechanical, cold, and heat hyperalgesia. Vincristine injection produced mechanical and cold hyperalgesia. For the GBE groups, the paw withdrawal threshold to mechanical stimuli was significantly increased and withdrawal frequency to cold stimuli was significantly reduced versus the control group dose-dependently (P < 0.05).

CONCLUSIONS

This study demonstrates that oral administration of GBE is associated with a dose-dependent antihyperalgesic effect on mechanical and cold stimuli in a rat model of vincristine-induced neuropathy.

Antinociceptive effect of Butea monosperma on vincristine-induced neuropathic pain model in rats

Neuropathic pain is a chronic neurodegenerative disease. It is well characterized by spontaneous pain, hyperalgesia, hypothesia, dysesthesia and allodynia. The present study was designed to investigate the antinociceptive potential of Butea monosperma on vincristine-induced painful neuropathy in rats. Vincristine was administered for induction of neuropathic pain in experimental animals. Hot plate, acetone drop, paw pressure, Von Frey hair and tail immersion tests were performed to assess the degree of thermal hyperalgesia, cold chemical allodynia, mechanical hyperalgesia and allodynia in the hind paw and tail thermal hyperalgesia, respectively, as an index of peripheral and central pain sensation. Tissue thiobarbituric acid reactive substances (TBARSs), reduced glutathione (GSH) and total calcium levels were estimated to assess the biochemical changes in the sciatic nerve tissue. Microscopically, histopathological changes were also observed in the sciatic nerve tissue. Ethanolic extract of B. monosperma leaves and pregabalin were administered for 14 consecutive days. Vincristine administration resulted in significant reduction in behavioural (i.e. hyperalgesia and allodynic pain sensation) changes along with a rise in the levels of TBARS, total calcium and decrease in GSH levels when compared with the normal control group. Moreover, significant histological changes were also observed. Pretreatment with B. monosperma significantly attenuated vincristine-induced development of painful behavioural, biochemical and histological changes in a dose-dependent manner, which is similar to that of pregabalin-pretreated group. B. monosperma ameliorated vincristine-induced painful neuropathy. It may be due to its potential of antioxidative, neuroprotective and calcium channel inactivation.

Endogenous opiates and behavior: 2010

This paper is the thirty-third consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2010 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration (Section 16); and immunological responses (Section 17).