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

Abstract

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.

Keywords

neuropathic pain pregabalin total calcium vincristine

Introduction

The vinca alkoloids (vincristine and vinblastine) are the most common chemotherapeutic agents used to treat a wide variety of malignancies, including leukemia and lymphoma and prevents tumour cell replication through alteration of cytoskeletal structure and disorientation of microtubules (Higuera and David Luo, 2004; Park et al., 2010). Vincristine-induced painful peripheral neuropathy is the major dose-limiting side effect and requires discontinuation of treatment, greatly impacting on the survival of cancer patients (Kaley and Deangelis, 2009; Sandler et al., 1969). Experimental models of vincristine-induced peripheral neuropathic pain have been established in rodents using different systemic dosing schedules of vincristine (Kaley and Deangelis, 2009; Park et al., 2010). It clinically mimics chemotherapy-associated neuropathic pain in human (Jaggi and Singh, 2010; Muthuraman et al., 2008a). Some preclinical and clinical reports promised to prevent neuropathic pain against chemotherapy-associated neurotoxicity, but none are yet approved for routine usage for the management of neurotoxic effects (Weimer and Sachdev, 2009). Vincristine administration-induced peripheral nerve injury is characterized by dysesthesia (abnormal and unpleasant sensation), hyperalgesia (an increased response to painful stimuli) and allodynia (pain in response to a stimulus that does not normally provoke pain; Woolf and Mannion, 1999).

Conventional analgesic and antineuralgic agents such as tricyclic antidepressants (i.e. amitriptyline, nortriptyline and imipramine), anticonvulsants (i.e. phenytoin, carbamazepine, gabapentin, lamotrigine and topiramate) and opioids have been reported to produce antiallodynic effects in neuropathic pain (Dworkin et al., 2010; Lee and Nandi, 2010). However, these medications have been documented as a wide spectrum of adverse effects which limit their full clinical exploitation in amelioration of the neuropathic pain (Carol and Jane, 2006; Wiffen et al., 2010). Various herbal medicines (e.g. Cannabis sativa, Ginkgo biloba, Ocimum sanctum, Aconiti tuber, Phyllanthus emblica and Nigella sativa) have been reported to possess the therapeutic potential for the management of various experimental models of neuropathic pain (Kim et al., 2009; Muthuraman et al., 2008b). Clinical reports have also claimed beneficial effects of herbal medicines in neuropathic pain conditions (Ellis et al., 2009; Nurmikko et al., 2007). Therefore, novel research urges to explore the newer herbal medicine in the management of neuropathic pain.

Butea monosperma (family: Fabaceae) also known as ‘Flame of the Forest’, is distributed in deciduous forest and in open areas (Lavhale and Mishra, 2007). The leaves, flowers, stem bark and seeds of B. monosperma have been used in traditional medicine as antidiabetic, antimicrobial, arthritis and wound healing actions (Krithikar and Basu, 1995; Varier, 1995).

Moreover, some traditional ayurvedic formulation of herbal species, that is, Emblica officinalis, Piper longum and B. monosperma have been documented as a nervine tonic and used for a life span of 100 years with full vigour, cognitive functions and to preserve youth (Adams et al., 2007; Manyam, 1999). Pippali rasayana (an ayurvedic herbal medicine) prepared from Piper longum and B. monosperma has been proved to play a major role in the immunomodulatory actions (Agarwal et al., 1994, 1997).

Experimentally, it has been proved that the leaves of B. monosperma possess the therapeutic potential role in the management of inflammation, epilepsy, anxiety, tumourogenesis and diabetes (Kasture et al., 2000; Mengi and Deshpande, 1995; Sehrawat and Sultana, 2006; Shahavi and Desai, 2008; Sharma and Garg, 2009; Soman et al., 2004). B. monosperma leaves possess the biologically active secondary metabolites such as euphane triterpenoid, flavonoids, tannins and phytosterols (Shukla et al., 2002). Fresh decoction of B. monosperma is commonly used to relieve muscular pain, joint pain and severe headache in some areas of Thiruvannamalai, Theni and Madurai regions in Tamil Nadu, India. An ayurvedic formulation namely Mahanarayana taila is used to treat neuralgia, which is prepared from this plant (Anonymous, 2006). However, experimentally, its analgesic potential in neuropathic pain remains unexplored.

Therefore, the present study was designed to investigate the antinociceptive potential of B. monosperma on vincristine-induced painful neuropathy in rats. Pregabalin (Lyrica™, Pfizer, India.) binds to the α2-δ site of an auxiliary subunit of voltage-gated calcium channels (N-type) in the central nervous system, inhibiting excitatory neurotransmitter release, and it has been reported to possess the potential management of neuropathic pain (Muthuraman et al., 2010). Therefore, pregabalin served as a positive control in this study.

Materials and methods

Plant material and extraction

Fresh leafy parts of B. monosperma were collected from Madurai and authenticated. Plant sample has been kept in the Department of Pharmacognosy (Voucher specimen no: BM. 001/2007-2008), Madurai Medical College, Madurai. The fresh leaves of B. monosperma was shade dried and reduced to coarse powder (sieve no. 10/40). The powdered leaves of B. monosperma (500 g) were defatted with petroleum ether and then extracted with ethanol (95%) in a Soxhlet apparatus as described by Suzgec-Selcuk and Birteksoz (2010). Ethanolic extract was concentrated under reduced pressure until dryness (yield 14.56%).

Chemicals

5,5′-Dithio, bis(2-nitrobenzoic acid), bovine serum albumin and reduced glutathione (GSH) were purchased from Sisco Research Laboratories (Mumbai). Thiobarbituric acid was purchased from Loba Chemie (Mumbai). All other reagents were used in analytical grade.

Animals

Wistar rats of either sex (180–250 g) were maintained on standard laboratory diet and water ad libitum. They were housed in the departmental animal house and exposed to 12 h light and dark cycle. The experimental protocol was approved by Institutional Animal Ethics Committee and animal care was as per the guidelines of Committee For the Purpose of Control and Supervision of Experiments on Animals (Ref. No. 2360/E2/4/2010).

Induction of peripheral neuropathy by vincristine

Painful peripheral neuropathy was induced in rats by the administration of vincristine sulfate (50 μg/kg; intraperitoneally (IP) once a day) for 10 consecutive days as described by Siau and Bennett (2006).

Experimental protocol

Nine groups, each comprising six Wistar rats, were employed in the present study.

Group I. Rats were not subjected to any drug or vehicle administration.

Group II. Rats were administered with vincristine (50 µg/kg; IP for 14 days).

Group III. Rats were administered with normal saline for 14 days.

Group IV. Rats were administered with ethanolic extract of B. monosperma (400 mg/kg; orally (p.o.)) to normal rats, for 14 days.

Group V. Rats were administered with pregabalin (10 mg/kg; p.o.) to normal rats, for 14 days.

Groups VI–VIII. Rats were administered with ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) 1 h before each vincristine injection, for 14 days.

Groups IX. Rats were administered with pregabalin (10 mg/kg; p.o.) 1 h before each vincristine injection, for 14 days.

The behavioural tests were performed on different time intervals, that is, 0, 1, 3, 6, 9, 12, 15, 18 and 21 days. Thereafter, all the animals were killed and subjected to biochemical estimation of the total protein, thiobarbituric acid reactive substance (TBARS), total calcium and reduced GSH in sciatic nerve tissue sample.

Behavioural assessment

Paw heat thermal sensitivity of the hind paw was assessed using Eddy’s hot plate method by Eddy et al. (1950). Paw cold chemical thermal sensitivity of the hind paw was assessed using acetone drop method as described by Choi et al. (1994). Paw mechanical sensation of the hind paw as an index of mechanical hyperalgesic test was assessed by the pressure stimulation method as described by Randall and Selitto (1957). Paw mechanical sensation of the hind paw as an index of mechanical allodynia was assessed as described by Chaplan et al. (1994). Spinal thermal sensitivity was assessed by the tail immersion test as described by Necker and Hellon (1978).

Biochemical estimation of markers of oxidative stress

At the end of the study protocol, animals were killed by cervical dislocation and the sciatic nerve was immediately isolated from the body. The sciatic nerve homogenate (10%, w/v) was prepared with 0.1 M Tris-HCl buffer (pH 7.4) and the supernatant of the homogenate was used to estimate total protein content, according to the method by Lowry et al. (1951); TBARSs (malondialdehyde (MDA)), as described by Okhawa et al. (1979); reduced GSH, as described by Ellman (1959), and total calcium content, as described by Severinghaus and Ferrebee (1950).

Histopathological evaluation

Samples of sciatic nerve were stored in the fixative solution (10% formalin) and cut into 4-µm thickness. Staining was done using hematoxylin and eosin as described by Sudoh et al. (2004). Nerve sections were analyzed qualitatively under light microscope (×450) for axonal degeneration.

Statistical analysis

All the results were expressed as mean ± SEM. The data from the behavioural results were statistically analyzed by two-way analysis of variance (ANOVA) followed by Bonferonni’s post hoc test using Graph pad prism Version-5.0 software. The data from the biochemical results were statistically analyzed by one-way ANOVA followed by Tukey’s multiple range tests. The p < 0.05 was considered to be statistically significant.

Results

Effect of B. monosperma on paw heat hyperalgesia

Vincristine administration resulted in significant development of noxious thermal hyperalgesia, noted by the decrease in hind paw withdrawal threshold, after day 3 when compared with normal control. Administration of ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) significantly attenuated vincristine-induced decrease in the nociceptive threshold for thermal hyperalgesia in a dose-dependent manner. Treatment of pregabalin also produced similar effects. However, statistically significant attenuation was recorded only in the groups treated with medium and high dose of B. monosperma. Furthermore, vehicle, B. monosperma per se and pregabalin did not show any significant effect on heat hyperalgesic test (Figure 1).

Effect of B. monosperma on paw cold allodynia

Vincristine administration resulted in significant development of non-noxious cold chemical allodynia, noted by the decrease in the left hind paw withdrawal threshold, after day 3 when compared with normal control. Administration of ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) significantly attenuated vincristine-induced decrease in the nociceptive threshold for thermal allodynia in a dose-dependent manner. Treatment of pregabalin also produced similar effects. However, statistically significant attenuation was recorded in only the groups treated with medium and high dose of B. monosperma. Furthermore, vehicle, B. monosperma per se and pregabalin did not show any significant effect on cold chemical allodynic test (Figure 2).

Effect of B. monosperma on paw mechanical hyperalgesia

Vincristine administration resulted in significant development of noxious static mechanical hyperalgesia, noted by the decrease in the left hind paw withdrawal threshold, after day 3 when compared with normal control. Administration of ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) significantly attenuated vincristine-induced decrease in the nociceptive threshold for mechanical hyperalgesia in a dose-dependent manner. Treatment of pregabalin also produced similar effects. However, statistically significant attenuation was recorded only in groups treated with medium and high dose of B. monosperma. Furthermore, vehicle, B. monosperma per se and pregabalin did not show any significant effect on mechanical hyperalgesic test (Figure 3).

Effect of B. monosperma on paw mechanical allodynia

Vincristine administration resulted in significant development of non-noxious tactile mechanical allodynia, noted by the decrease in the left hind paw withdrawal threshold, after day 3 when compared with normal control. Administration of ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) significantly attenuated vincristine-induced decrease in the nociceptive threshold for mechanical allodynia in a dose-dependent manner. Treatment of pregabalin also produced similar effects. However, statistically significant attenuation was recorded only with medium and high dose of B. monosperma-treated groups. Furthermore, vehicle, B. monosperma per se and pregabalin did not show any significant effect on mechanical allodynic test (Figure 4).

Effect of B. monosperma on tail heat hyperalgesia

Vincristine administration resulted in significant development of noxious thermal hyperalgesia, noted by the decrease in the tail withdrawal threshold, after day 3 when compared with normal control. Administration of ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) significantly attenuated vincristine-induced decrease in the nociceptive threshold for mechanical hyperalgesia in a dose-dependent manner. Treatment of pregabalin also produced similar effects. However, statistically significant attenuation was recorded only in groups with medium and high dose of B. monosperma. Furthermore, vehicle, B. monosperma per se and pregabalin did not show any significant effect on tail heat hyperalgesic test (Figure 5).

Effect of B. monosperma on tissue biomarker changes

Vincristine administration resulted in significant rise in TBARS, total calcium levels and decreased in the levels of reduced GSH, after day 21 when compared with normal control. However, total protein levels were not affected significantly as a result of vincristine. Administration of the ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) significantly attenuated vincristine-induced rise in sciatic nerve tissue MDA, total calcium and decrease in reduced GSH levels in a dose-dependent manner. However, B. monosperma resulted in normalization of vincristine-induced biochemical abnormalities in a significant manner. Treatment of pregabalin also produced similar effects. Furthermore, vehicle, B. monosperma per se and pregabalin did not show any significant effect on oxidative stress markers (Table 1).

Table 1.

Effect of Butea monosperma on tissue biomarker changes.^a

Groups	MDA (nmol/mg of protein)	GSH (µg/mg of protein)	Total calcium (ppm/mg of protein)
Normal	3.18 ± 0.61	76.19 ± 1.92	2.62 ± 0.31
VIN	4.57 ± 0.53^b	47.57 ± 3.68^b	21.48 ± 0.25^b
Vehicle in VIN	4.53 ± 0.18^b	48.32 ± 3.92^b	20.71 ± 0.48^b
B. monosperma (400 mg/kg) per se	3.21 ± 0.46	75.83 ± 2.39	2.73 ± 0.26
Pregabalin (10 mg/kg) per se	3.20 ± 0.51	76.13 ± 2.04	2.82 ± 0.45
B. monosperma (200 mg/kg) in VIN	4.38 ± 0.27^bc	51.37 ± 2.12^bc	18.94 ± 0.52^bc
B. monosperma (300 mg/kg) in VIN	3.96 ± 0.62^d	63.18 ± 2.41^d	10.93 ± 0.32^d
B. monosperma (400 mg/kg) in VIN	3.33 ± 0.41^d	70.24 ± 1.58^d	6.85 ± 0.52^d
Pregabalin (10 mg/kg) in VIN	3.29 ± 0.35^d	73.84 ± 1.74^d	4.57 ± 0.42^d

MDA: malondialdehyde; GSH: glutathione; VIN: vincristine.

^aLevels of MDA, GSH, and total calcium were determined in sciatic nerve of different groups. Data were expressed as mean ± SEM, n = 6 rats per group.

^b p < 0.05 versus normal control group.

^c p < 0.05 versus pregabalin-treated group.

^d p < 0.05 versus B. monosperma control group.

Effect of B. monosperma on histopathological changes

Vincristine administration resulted in significant histopathological changes that are assessed in transverse section of the sciatic nerve. In transverse section, nerve derangement, axonal swelling and increase in the number of Schwann and satellite cells were also noted. Administration of the ethanolic extract of B. monosperma (200, 300 and 400 mg/kg; p.o.) significantly attenuated vincristine-induced axonal degeneration and histopathological alterations (Figure 6).

Discussion

In the present study, ethanolic extract of B. monosperma significantly attenuated vincristine-induced behavioural (i.e. paw and tail heat hyperalgesia, cold allodynia, mechanical hyperalgesia and mechanical allodynia) and biochemical (TBARS, total calcium and reduced GSH) as well as histopathological changes. The behavioural alterations started from day 3 and maximal nociceptive threshold was observed on day 9 by vincristine (50 µg/kg; IP once a day, for 10 consecutive days) administration. These observations are in line with the earlier findings of our colleagues (Muthuraman et al., 2008a, 2010) and reports from the other laboratories (Sweitzer et al., 2006; Topp et al., 2000).

Vincristine has been widely used for the management of various life-threatening cancer disorders including Hodgkin’s disease. However, its clinical application has been limited due to unavoidable painful ‘dying-back’ neuropathy. It possesses the property of high binding affinity towards β-tubulin of microtubules of peripheral nervous system. Microtubules are key components of the cytoskeleton and are composed of heterodimers of α-tubulin and β-tubulin, which assemble into linear, hollow, cytoplasmic filaments (Schwartz, 2009). Vincristine has been documented to cause disruption of microtubule polymerizations leading to destabilize microtubules, block proliferation by cell cycle arrest and cause cell death via the induction of apoptosis for its chemotherapeutic as well as neurotoxic actions (Jordan and Wilson, 2004).

Furthermore, Vincristine has also been reported to alter the cellular Ca²⁺ and free radical levels (Kamei et al., 2005; Siau and Bennett, 2006), which play a key role in the pathogenesis of painful dying-back neuropathy associated with vincristine. Calcium-induced free radical generation have been implicated to potential neuronal injury (Muthuraman et al., 2008a, 2008b, 2010; Muthuraman and Sood, 2010). Calcium accumulation has been triggered as a self-destructive cascade via calcium-binding protein such as calmodulin and calpain leading to neuronal hyperexcitability, adenosine triphosphate depletion, free radical generation and activation of cytosolic phospholipases and proteases (Muthuraman et al., 2008a, 2008b, 2010; Xie and Barrett, 1991; Young, 1992). Calcium-induced activation of calpains has also been reported to degrade axonal cytoskeleton resulting in the axonal degeneration via β-tubulin polymerization (Glass et al., 2002). In turn, free radicals are also documented to induce potential tissue damage and painful neuropathy (Park et al., 2010; Muthuraman et al., 2008a). Moreover, calcium accumulation and free radical generations have been documented as a major culprit event in various types of neuropathic pain disorders like posttraumatic, axotomy, anti-HIV drugs, tibial sural transaction, chronic constriction injury, ischemic–reperfusion injury and vincristine-induced neuropathy (Muthuraman et al., 2008a, 2008b , 2010). In the present study, vincristine treatment resulted in the rise in the levels of TBARS (an index of lipid peroxidation) and total calcium and fall in the reduced GSH (an endogenous antioxidant molecule), thus supporting the contention that free radicals may contribute in pathogenesis of neuropathy. Moreover, the administration of ethanolic extract of B. monosperma significantly attenuated the vincristine-induced alterations of peripheral and central behavioural and oxidative stress marker changes as well as histopathological changes. Experimentally, B. monosperma has been documented to decrease free radical generation via enhancement of antioxidant mechanisms (Sai Krishna et al., 2010). The decrease in calcium levels with B. monosperma may be attributed to its antioxidant effects via free radical scavenging and calcium channel inhibitory actions (Lavhale and Mishra, 2007). However, the possibility of direct action of B. monosperma on calcium channel and decrease in calcium levels may not also be ruled out. However, number of experimental reports indicates antioxidant effects of B. monosperma in various studies (Lavhale and Mishra, 2007; Sai Krishna et al., 2010; Sharrna and Garg, 2009). B. monosperma has significantly attenuated vincristine-induced hyperalgesic and allodynic pain sensation and biochemical as well as histopathological changes. Similar results were obtained in the pregabalin-treated animals. Pregabalin is a potential voltage-dependent N-type calcium channel blocker (selectively bind to α2-δ subunit; Kumar et al., 2010). It has also been reported to possess the potential role in the management of painful neuropathy in human as well as in experimental animal (Bender et al., 2010; Muthuraman et al., 2011). Ameliorative effect of B. monosperma against vincristine-induced neuropathic pain may be due to its free radical scavenging and calcium channel modulatory actions. Nevertheless, further studies are needed to substantiate these findings.

Conclusion

Hence, ethanolic extract of B. monosperma possesses the therapeutic potential on vincristine-induced behavioural, biochemical and histopathological changes in rats. These ameliorative effects may be attributed due to its antioxidative, anti-inflammatory, neuroprotective and calcium channel inactivating potential.

Footnotes

Acknowledgements

The authors thank Drs N. Chidambara Nathan, Department of Pharmacology, K.M. College of Pharmacy, Madurai, K. Raadhika, Institute of Pharmacology, Madurai Medical College, Madurai, for their valuable suggestions and support to carry out this work.

Conflict of interest

The authors declared no conflicts of interest.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

References

Adams

Gmünder

Hamburger

(2007) Plants traditionally used in age related brain disorders—a survey of ethnobotanical literature. Journal of Ethnopharmacology 113(3): 363–381.

Agarwal

Singh

Gupta

. (1994) Management of giardiasis by an immuno-modulatory herbal drug Pippali rasayana. Journal of Ethnopharmacology 44(3): 143–146.

Agarwal

AK.

Tripathi

Sahai

. (1997). Management of giardiasis by a herbal drug Pippali Rasayana: a clinical study. Journal of Ethnopharmacology 56(3): 233–236.

Anonymous (2006) The Ayurvedic Pharmacopoeia of India. New Delhi: Government of India, pp. 128–130.

Bender

Florian

Jr Bramwell

. (2010) Pharmacokinetic-pharmacodynamic analysis of the static allodynia response to pregabalin and sildenafil in a rat model of neuropathic pain. Journal of Pharmacology and Experimental Therapeutics 334(2): 599–608.

Carol

Jane

(2006) Evidence-based treatment of diabetic peripheral neuropathy. Journal of Nurse Practitioners 2: 370–378.

Chaplan

Bach

Pogrel

Chung

Yaksh

(1994) Quantitative assessment of tactile allodynia in the rat paw. Journal of Neuroscience Methods 53(1): 55–63.

Choi

Yoon

Kim

Chung

(1994) Behavioral signs of ongoing pain and cold allodynia in a rat model of neuropathic pain. Pain 59(3): 369–376.

Dworkin

O’Connor

Audette

. (2010) Recommendations for the pharmacological management of neuropathic pain: an overview and literature update. Mayo Clinic Proceedings 85(3 suppl): S3–S14.

10.

Eddy

Touchberry

Lieberman

(1950) Synthetic analgesics: I. Methadone isomers and derivatives. Journal of Pharmacology and Experimental Therapeutics 98(2): 121–137.

11.

Ellis

Toperoff

Vaida

. (2009) Smoked medicinal cannabis for neuropathic pain in HIV: a randomized, crossover clinical trial. Neuropsychopharmacology 34(3): 672–680.

12.

Ellman

(1959) Tissue sulfhydryl groups. Archives of Biochemistry and Biophysics 82: 70–77.

13.

Glass

Culver

Levey

Nash

(2002) Very early activation of m-calpain in peripheral nerve during Wallerian degeneration. Journal of Neurological Science 196(1-2): 9–20.

14.

Lavhale

Mishra

(2007) Evaluation of free radical scavenging activity of Butea monosperma Lam. Indian Journal of Experimental Biology 45(4): 376–384.

15.

Higuera

David Luo

(2004) A rat pain model of vincristine-induced neuropathy. Methods in Molecular Medicine 99: 91–98.

16.

Jaggi

Singh

(2010) Differential effect of spironolactone in chronic constriction injury and vincristine-induced neuropathic pain in rats. European Journal of Pharmacology 648(1-3): 102–109.

17.

Jordan

Wilson

(2004) Microtubules as a target for anticancer drugs. Nature Reviews. Cancer 4(4): 253–265.

18.

Kaley

Deangelis

(2009) Therapy of chemotherapy-induced peripheral neuropathy. British Journal of Haematology 145(1): 3–14.

19.

Kamei

Tamura

Saitoh

(2005) Possible involvement of the spinal nitric oxide/cGMP pathway in vincristine-induced painful neuropathy in mice. Pain 117(1-2): 112–120.

20.

Kasture

Chopde

Deshmukh

. (2000) Anticonvulsive activity of Albizzia lebbeck, Hibiscus rosasinensis, and Butea monosperma in experimental animals. Journal of Ethnopharmacology 71(1-2): 65–75.

21.

Kim

Park

Kim

Moon

Lee

(2009) The effects of Ginkgo biloba extract EGb 761 on mechanical and cold allodynia in a rat model of neuropathic pain. Anesthesia and Analgesia 108(6): 1958–1963.

22.

Krithikar

Basu

(1995) Butea monosperma. In: Blatter

Caius

Mahaskar

(eds) Indian Medicinal Plants. Dehradun: Shiva Offset Press, pp. 785–788.

23.

Kumar

Laferriere

Leavitt

Coderre

(2010) Evidence that pregabalin reduces neuropathic pain by inhibiting the spinal release of glutamate. Journal of Neurochemistry 113(2): 552–561.

24.

Lee

Nandi

(2010) Improving the management of neuropathic pain. Practitioner 254(1731): 27–30.

25.

Lowry

Rosenbrough

Farr

Randall

(1951) Protein measurement with folin phenol reagent. Journal of Biological Chemistry 193(1): 265–275.

26.

Manyam

(1999) Dementia in ayurveda. Journal of Alternative and Complementary Medicine 5(1): 81–88.

27.

Mengi

Deshpande

(1995) Evaluation of ocular anti-inflammatory activity of Butea frondosa . Indian Journal of Pharmacology 27: 116–119.

28.

Muthuraman

Jaggi

Singh

(2008a) Ameliorative effects of amiloride and pralidoxime in chronic constriction injury and vincristine-induced painful neuropathy in rats. European Journal of Pharmacology 587(1-3): 104–111.

29.

Muthuraman

Diwan

Jaggi

Singh

(2008b) Ameliorative effects of Ocimum sanctum in sciatic nerve transection induced neuropathy in rats. Journal of Ethnopharmacology 120(1): 56–62.

30.

Muthuraman

Singh

Jaggi

(2011) Effect of hydroalcoholic extract of Acorus calamus on tibial and sural nerve transection-induced painful neuropathy in rats. Journal of Natural Medicine 65(2): 282–292.

31.

Muthuraman

Ramesh

Sood

(2010) Development of animal model for vasculatic neuropathy: induction by ischemic-reperfusion in the rat femoral artery. Journal of Neuroscience Methods 186(2): 215–221.

32.

Muthuraman

Sood

(2010) Pharmacological evaluation of tacrolimus (FK-506) on ischemia reperfusion induced vasculatic neuropathic pain in rats. Journal of Brachial Plexus Peripheral Nerve Injury 5: 13–23.

33.

Necker

Hellon

(1978) Noxious thermal input from the rat tail: modulation by descending inhibitory influences. Pain 4(3): 231–242.

34.

Nurmikko

Serpell

Hoggart

Toomey

Morlion

Haines

(2007) Sativex successfully treats neuropathic pain characterised by allodynia: a randomised, double-blind, placebo-controlled clinical trial. Pain 133(1-3): 210–220.

35.

Okhawa

Ohishi

Yagi

(1979) Assay for lipid peroxidation in animal tissue by thiobarbituric acid reaction. Analytical Biochemistry 95: 351–358.

36.

Park

Joo

Chang

. (2010) Antinociceptive effect of memantine and morphine on vincristine-induced peripheral neuropathy in rats. Korean Journal of Pain 23(3): 179–185.

37.

Randall

Selitto

(1957) A method for measurement of analgesic activity of inflamed tissue. Archives Internationales de Pharmacodynamie et de Therapie 111: 209–219.

38.

Sai Krishna

Ranganayakulu

Sujatha

Pushpa kumara

Venkateswarulu

GopiChand

Chinta

(2010) Anti-oxidant activity of the Butea monosperma leaves alone and in combination with atrovastatin. Drug Invention Today 2: 149–151.

39.

Sandler

Tobin

Henderson

(1969) Vincristine-induced neuropathy. A clinical study of fifty leukemic patients. Neurology 19(4): 367–374.

40.

Schwartz

(2009) Antivascular actions of microtubule-binding drugs. Clinical Cancer Research 15(8): 2594–2601.

41.

Sehrawat

Sultana

(2006) Chemoprevention by Butea monosperma of hepatic carcinogenesis and oxidative damage in male Wistar rats. Asian Pacific Journal of Cancer Prevention 7(1): 140–148.

42.

Severinghaus

Ferrebee

(1950) Calcium determination by flame photometry; methods for serum, urine, and other fluids. Journal of Biological Chemistry 187(2): 621–630.

43.

Shahavi

Desai

(2008) Anti-inflammatory activity of Butea monosperma flowers. Fitoterapia 79(2): 82–85.

44.

Sharma

Garg

(2009) Antidiabetic and antioxidant potential of ethanolic extract of Butea monosperma leaves in alloxan-induced diabetic mice. Indian Journal of Biochemistry and Biophysics 46(1): 99–105.

45.

Sharrna

Garg

(2009) Antihyperglycemic and antioxidative potential of hydroalcoholic extract of Butea monosperma. Lam. flowers in alloxan-induced diabetic mice. Indian Journal of Experimental Biology 47(7): 571–576.

46.

Shukla

Mishra

Sushil

(2002) Euphane triterpenoid ester and a pterocarpan fron Butea monosperma leaves. Indian Journal of Chemistry 41B: 881–883.

47.

Siau

Bennett

(2006) Dysregulation of neuronal calcium homeostasis in chemotherapy-evoked painful peripheral neuropathy. Anesthesia and Analgesia 102(5): 1485–1490.

48.

Soman

Mengi

Kasture

(2004) Effect of leaves of Butea frondosa on stress, anxiety, and cognition in rats. Pharmacology, Biochemistry, and Behavior 79(1): 11–16.

49.

Sudoh

Desai

Haderer

. (2004) Neurologic and histopathologic evaluation after high volume intrathecal amitriptyline. Regional Anesthesia and Pain Medicine 29(5): 434–440.

50.

Suzgec-Selcuk

Birteksoz

(2010) Flavonoids of Helichrysum chasmolycicum and its antioxidant and antimicrobial activities. South African Journal of Botany 77: 170–174.

51.

Sweitzer

Pahl

DeLeo

(2006) Propentofylline attenuates vincristine-induced peripheral neuropathy in the rat. Neuroscience Letters 400(3): 258–261.

52.

Topp

Tanner

Levine

(2000) Damage to the cytoskeleton of large diameter sensory neurons and myelinated axons in vincristine induced painful peripheral neuropathy in the rat. Journal of Comparative Neurology 424(4): 563–576.

53.

Varier

SPV

(1995) Indian Medicinal Plants. Madras: Long Man Publisher.

54.

Weimer

Sachdev

(2009) Update on medication-induced peripheral neuropathy. Current Neurology and Neuroscience Reports 9(1): 69–75.

55.

Wiffen

Collins

McQuay

Carroll

Jadad

Moore

(2010) WITHDRAWN. Anticonvulsant drugs for acute and chronic pain. Cochrane Database of Systemic Reviews 1: CD001133.

56.

Woolf

Mannion

(1999) Neuropathic pain: aetiology, symptoms, mechanisms, and management. Lancet 353(9168): 1959–1964.

57.

Xie

Barrett

(1991) Membrane resealing in cultured rat septal neurons after neurite transection: evidence for enhancement by Ca(2+)-triggered protease activity and cytoskeletal disassembly. Journal of Neuroscience 11(10): 3257–3267.

58.

Young

(1992) Role of calcium in central nervous system injuries. Journal of Neurotrauma 9(suppl 1): 9–25.