Pain-relieving effects of processed Aconiti tuber in CCI-neuropathic rats

A review on efforts for improvement in medicinally important chemical constituents inAconitum through biotechnological interventions

The genus Aconitum belongs to the family Ranunculaceae, is endowed with more than 350 species on the earth. Medicinally important aconitine type of diterpenoid alkaloids are the characteristic compounds in most of the Aconitum species. The present review endeavored the major research carried out in the field of genetic resource characterization, pharmacological properties, phytochemistry, major factors influencing quantity, biosynthetic pathways and processing methods for recovery of active ingredients, variety improvement, propagation methods, and important metabolite production through cell/organ culture of various Aconitum species. More than 450 derivatives of aconitine-type C19 and C20-diterpenoid alkaloids along with a few other non-alkaloidal compounds, such as phenylpropanoids, flavonoids, terpenoids, and fatty acids, have been identified in the genus. A few Aconitum species and their common diterpenoid alkaloid compounds are also well characterized for analgesic, inflammatory and cytotoxic properties. However, the different isolated compound needs to be validated for supporting other traditional therapeutical uses of the plant species. Aconitine alkaloids shared common biosynthesis pathway, but their diversification mechanism remains unexplored in the genus. Furthermore, the process needs to be developed on secondary metabolite recovery, mass-scale propagation methods, and agro-technologies for maintaining the quality of products. Many species are losing their existence in nature due to over-exploitation or anthropogenic factors; thus, temporal monitoring of the population status in its habitat, and suitable management programs for ascertaining conservation needs to be developed.

N-type calcium channel blockers: a new approach towards the treatment of chronic neuropathic pain

Neuropathic pain (NP) remains maltreated for a wide number of patients by the currently available treatments and little research has been done in finding new drugs for treating NP. Ziconotide (PrialtTM) had been developed as the new drug, which belongs to the class of ω-conotoxin MVIIA. It inhibits N-type calcium channels. Ziconotide is under the last phase of the clinical trial, a new non-narcotic drug for the management of NP. Synthetically it has shown the similarities with ω-conotoxin MVIIA, a constituent of poison found in fish hunting snails (Conus magus). Ziconotide acts by selectively blocking neural N-type voltage-sensitized Ca2+ channels (NVSCCs). Certain herbal drugs also have been studied but no clinical result is there and the study is only limited to preclinical data. This review emphasizes the N-type calcium channel inhibitors, and their mechanisms for blocking calcium channels with their remedial prospects for treating chronic NP.

Global Research Trends of Herbal Medicine for Pain in Three Decades (1990-2019): A Bibliometric Analysis

Purpose

The aim of this study was to explore the global research trends of herbal medicine for pain from 1990 to 2019, using bibliometric methods, and explore international collaborations, intellectual structure, the evolution of active topics, emerging trends, and research frontiers.

Methods

Articles on herbal medicine for pain were retrieved from WoSCC. Two information visualization softwares including CiteSpace and HistCite were used to process bibliographic catalogs. Identification of international collaborations, intellectual structure, the evolution of active topics, emerging trends, and research frontiers were performed based on results from bibliometric analysis.

Results

A total of 2986 original articles published between 1990 and 2019 were identified based on the inclusion criteria. The number of publications on herbal medicine for pain in WoSCC significantly increased. China ranked highest in the number of scientific outputs; however, articles with the highest citation rates were found to be from the United States. China–Japan reported the most active collaborations, whereas Kyung Hee University from South Korea was the most productive institution. Zhang Y was the most productive author, whereas research by Sherman KJ and Vane JR had the highest influence. Journal of Ethnopharmacology was the most active journal, whereas Integrative and Complementary Medicine was the most active research area. History of herbal medicine for pain research comprises three major phases of activities. The main points of focus of bibliometric analysis of herbal medicine for pain include “knee osteoarthritis”, “cancer”, “low back pain”, etc.. Moreover, research on mechanisms of action of herbal medicine for pain remains at the forefront of this field.

Conclusion

This paper provides a basis for future development of research on herbal medicine for pain, which may help researchers explore new directions for future research and identify new perspectives on potential collaborations in this field.

Effect of herbal extracts on peripheral nerve regeneration after microsurgery of the sciatic nerve in rats

Background

Recent experimental studies using herbal extracts have shown the possibility of peripheral nerve regeneration. This study aimed to investigate the effects of herbal extracts on peripheral nerve regeneration in a rat sciatic nerve injury model.

Methods

A total of 53 rats were randomly assigned to a control group or one of four experimental groups. In all rats, the sciatic nerve was completely severed and microscopic epineural end-to-end neurorrhaphy was performed. Normal saline (2 mL) was topically applied to the site of nerve repair in the control group, whereas four different herbal extracts – 2 mL each of Astragalus mongholicus Bunge, Coptis japonica (Thunb.) Makino, Aconitum carmichaelii Debeaux, or Paeonia lactiflora Pall. – were topically applied to the site of nerve repair in each experimental group. Nerve conduction studies were performed at an average of 11.9 weeks after the operation, and conduction velocity and proximal and distal amplitudes were measured. Biopsies were performed at an average of 13.2 weeks after the initial neurorrhaphy. The quality of nerve anastomosis and perineural adhesion to the surrounding soft tissues was macroscopically evaluated. The neuroma size at the site of the neurorrhaphy was microscopically measured, whereas the size of the scar tissue was evaluated relative to the diameter of the repaired nerve.

Results

The nerve conduction study results showed the highest nerve conduction velocity in the experimental group that used the Coptis japonica (Thunb.) Makino extract and the highest proximal and distal amplitudes in the experimental group that used the Aconitum carmichaelii Debeaux extract. Macroscopic evaluations after the second operation showed that grade 2 perineural adhesion was found in 70.8% of rats. The mean neuroma size in the Coptis japonica (Thunb.) Makino, Aconitum carmichaelii Debeaux, and Paeonia lactiflora Pall. groups showed statistically significant decreases relative to the control group. The mean scar tissue formation index in the Paeonia lactiflora Pall. group showed a statistically significant decrease relative to the control group.

Conclusions

The peripheral nerve regeneration effect of the herbal extracts was confirmed through decreased neuroma and scar tissue formation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03335-w.

An Effective Phytoconstituent Aconitine: A Realistic Approach for the Treatment of Trigeminal Neuralgia

Trigeminal neuralgia pain remains a challenge to treat. Natural compounds may be promising options for relieving pain. This study was aimed at investigating the effects of aconitine in a rat model of trigeminal neuralgia pain. Infraorbital nerve chronic constriction injury was performed in adult Wistar Albino rats. After the neuropathic pain developed, the rats were assigned to one of the treatment groups: carbamazepine 40 or 80 mg/kg; aconitine 0.25, 0.50, or 0.75 mg/kg; or saline injection (control group). Behavioral testing with von Frey filaments and the rotarod test were carried out before the surgical procedure and on the 24th to 29th postoperative days. Following the completion of tests, ipsilateral and contralateral spinal cords were harvested for Western blot analyses to assess NR-1 protein expression. ANOVA followed by Mann-Whitney U test was performed for the statistical analyses. P values of <0.05 were considered significant. Aconitine significantly reduced mechanical sensitivity in a dose-dependent manner. A significant reduction in motor coordination was noted for the higher doses of aconitine which was similar with the 40 and 80 mg/kg doses of carbamazepine. NR-1 expression was reduced in the ipsilateral spinal cord, whereas no significant difference was noted between the groups in the expression of NR-1 in the contralateral spinal cord. Aconitine had a significant pain relieving effect, which was similar to carbamazepine, in a dose-dependent manner. Aconitine may be an alternative pharmacological agent for the control of trigeminal neuralgia pain.

Effects of processed Aconiti tuber on the extinction and reinstatement of morphine-induced conditioned place preference in rats

AIM OF THE STUDY

To investigate the effect of processed Aconiti tuber (PAT) administered during or after the time of conditioned place preference (CPP) training on the extinction and reinstatement of morphine-priming CPP in rats. The dynorphin level in rats' nucleus accumbens (NAc) is detected as a target of the Dynorphin/Kappa Opioid Receptor (KOR) system for the possible mechanism.

MATERIALS AND METHODS

Eight groups of rats were subcutaneously (s.c.) injected with morphine (10mg/kg) (on days 2,4,6,8) or saline (1ml/kg) (on days 3,5,7,9) alternately for 8 days. Five groups, including groups (Mor + Water, Mor + PAT (1.0/3.0g/kg) (S) and Sal + PAT(1.0/3.0g/kg)), were orally given distilled water or PAT 1.0 or 3.0 g/kg daily on days 1-8 during CPP training while other three groups, including groups (Sal + Water and Mor + PAT (1.0/3.0g/kg)(P), were given distilled water or PAT daily from day 10 until CPP was extinct. Morphine 1mg/kg (s.c.) was used to reinstate the extinct CPP and the CPP scores were recorded. The dynorphin concentration in nucleus accumbens (NAc) was assayed by radioimmunoassay after the last CPP measurement.

RESULTS

1) The CPP extinction shortened in Mor + PAT (1.0/3.0 g/kg) (S) groups but extended in Mor + PAT (1.0/3.0 g/kg)(P) groups. 2) Morphine-priming CPP did not change either in Mor + PAT (1.0/3.0 g/kg) (S) or Mor + PAT (1.0/3.0 g/kg)(P) groups. 3) The dynorphin concentration in NAc increased either in Mor + PAT (1.0/3.0 g/kg)(S) or Mor + PAT (1.0/3.0 g/kg)(P) groups.

CONCLUSIONS

1) PAT shortened the extinction from morphine induced CPP when administrated before CPP acquisition, whereas it extended the extinction when administrated after CPP formation. 2) PAT administrated during or after CPP training did not affect morphine-priming reinstatement of morphine induced CPP. 3) Dynorphin/KOR system might be a target to regulate morphine-induced CPP extinction but not reinstatement.

Effects of alkaloids on peripheral neuropathic pain: a review

Neuropathic pain is a debilitating pathological pain condition with a great therapeutic challenge in clinical practice. Currently used analgesics produce deleterious side effects. Therefore, it is necessary to investigate alternative medicines for neuropathic pain. Chinese herbal medicines have been widely used in treating intractable pain. Compelling evidence revealed that the bioactive alkaloids of Chinese herbal medicines stand out in developing novel drugs for neuropathic pain due to multiple targets and satisfactory efficacy. In this review, we summarize the recent progress in the research of analgesic effects of 20 alkaloids components for peripheral neuropathic pain and highlight the potential underlying molecular mechanisms. We also point out the opportunities and challenges of the current studies and shed light on further in-depth pharmacological and toxicological studies of these bioactive alkaloids. In conclusion, the alkaloids hold broad prospects and have the potentials to be novel drugs for treating neuropathic pain. This review provides a theoretical basis for further applying some alkaloids in clinical trials and developing new drugs of neuropathic pain.

Neoline, an active ingredient of the processed aconite root in Goshajinkigan formulation, targets Nav1.7 to ameliorate mechanical hyperalgesia in diabetic mice

ETHNOPHARMACOLOGICAL RELEVANCE

Goshajinkigan (GJG), a traditional Japanese Kampo formula, has been shown to exhibit several pharmacological actions, including antinociceptive effects. Processed aconite root (PA), which is considered to be an active ingredient of GJG, has also been demonstrated to have an ameliorative effect on pain, such as diabetic peripheral neuropathic pain. We recently identified neoline as the active ingredient of both GJG and PA that is responsible for its effects against oxaliplatin-induced neuropathic pain in mice.

AIM OF THE STUDY

In the present study, we investigated whether GJG, PA, and neoline could inhibit Nav1.7 voltage-gated sodium channel (VGSC) current and whether neoline could ameliorate mechanical hyperalgesia in diabetic mice.

MATERIALS AND METHODS

To assess the electrophysiological properties of GJG extract formulation, powdered PA, and neoline on Nav1.7 VGSCs, whole-cell patch clamp recording was performed using human HEK293 cells expressing Nav1.7 VGSCs. In addition, the ameliorative effects of neoline on diabetic peripheral neuropathic pain were evaluated using the von Frey test in streptozotocin (STZ)-induced diabetic model mice.

RESULTS

GJG extract formulation significantly inhibited Nav1.7 VGSC peak current. Powdered PA also inhibited Nav1.7 VGSC peak current. Like GJG and PA, neoline could inhibit Nav1.7 VGSC current. When diabetic mice were treated with neoline by intraperitoneal acute administration, the mechanical threshold was increased in diabetic mice, but not in non-diabetic mice, in a behavioral study.

CONCLUSION

These results suggest that neoline might be a novel active ingredient of GJG and PA that is one of responsible ingredients for ameliorating mechanical hyperalgesia in diabetes via the inhibition of Nav1.7 VGSC current at least.

KCHO-1, a novel herbal anti-inflammatory compound, attenuates oxidative stress in an animal model of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by selective death of motor neurons in the central nervous system. The main cause of the disease remains elusive, but several mutations have been associated with the disease process. In particular, mutant superoxide dismutase 1 (SOD1) protein causes oxidative stress by activating glia cells and contributes to motor neuron degeneration. KCHO-1, a novel herbal combination compound, contains 30% ethanol and the extracts of nine herbs that have been commonly used in traditional medicine to prevent fatigue or inflammation. In this study, we investigated whether KCHO-1 administration could reduce oxidative stress in an ALS model. KCHO-1 administered to ALS model mice improved motor function and delayed disease onset. Furthermore, KCHO-1 administration reduced oxidative stress through gp91phox and the MAPK pathway in both classically activated microglia and the spinal cord of hSOD1G93A transgenic mice. The results suggest that KCHO-1 can function as an effective therapeutic agent for ALS by reducing oxidative stress.

Preparation and physicochemical characterization of ingredients of Indian traditional medicine, Mahamrutyunjaya Rasa

Background

Mahamrutyunjaya rasa is an ayurvedic formulation used in the treatment of cardiac disorders. It contains the purified roots of Visa (Aconitum ferox), Brihati (Solanum indicum), fruits of Pippali Kana (Piper longum), Marica (Piper nigrum), Gandhaka (Sulfur), Hingula (Cinnabar) and Tankana (Sodium metaborate) as per Bhaishajya Ratnavali. The purification (shodhana) process changes the physiochemical properties of the raw materials which need to be studied and understood.

Objective

The present work aims to perform a comprehensive physicochemical characterization of raw materials, intermediates and the final product obtained during purification, using modern analytical techniques.

Materials and methods

The standard methods as per traditional text were followed and the physicochemical changes were also investigated by collecting samples at different steps of purification. The samples were analysed using various techniques, viz. Fourier transform infra-red spectroscopic (FTIR), X-ray diffraction (XRD), Differential Scanning Calorimeter (DSC) and High Performance thin Layer chromatography (HPTLC).

Results

The FTIR and HPTLC analysis of the alkaloidal extracts of Visa showed loss of an ester group with shift in the peaks from 1720 cm⁻¹ (C Created by potrace 1.16, written by Peter Selinger 2001-2019 ]]>O stretching of esters) to 1676 cm⁻¹ (CO stretching of Ketone) which signifies the conversion of alkaloid Aconitine (LD₅₀ – 0.08 mg/kg) to Benzoylaconine (LD₅₀ – 24 mg/kg) improving its safety. The analysis of gandhaka by XRD and DSC showed that purification brought about transformation of orthorhombic sulphur into monoclinic sulphur and it reverted back to original form with higher purity. The treatments given to gandhaka and hingula with organic compounds made them homologous to the body tissues. Analysis of purified tankana showed that the processing led to loss of water and slight change in the crystal structure with the shift in the endothermic peak from 110.6 °C to 104.2 °C.

Conclusion

Thus, the present study provides a scientific backing to the methodologies used by Ayurvedic practitioners. The study also provides physicochemical fingerprints for the standardization as well as characterization of raw materials and forms a technical platform for manufacturers to develop quality control standards.

Molecular signaling underlying bulleyaconitine A (BAA)-induced microglial expression of prodynorphin

Bulleyaconitine (BAA) has been shown to possess antinociceptive activities by stimulation of dynorphin A release from spinal microglia. This study investigated its underlying signal transduction mechanisms. The data showed that (1) BAA treatment induced phosphorylation of CREB (rather than NF-κB) and prodynorphin expression in cultured primary microglia, and antiallodynia in neuropathy, which were totally inhibited by the CREB inhibitor KG-501; (2) BAA upregulated phosphorylation of p38 (but not ERK or JNK), and the p38 inhibitor SB203580 (but not ERK or JNK inhibitor) and p38β gene silencer siRNA/p38β (but not siRNA/p38α) completely blocked BAA-induced p38 phosphorylation and/or prodynorphin expression, and antiallodynia; (3) BAA stimulated cAMP production and PKA phosphorylation, and the adenylate cyclase inhibitor DDA and PKA inhibitor H-89 entirely antagonized BAA-induced prodynorphin expression and antiallodynia; (4) The Gs-protein inhibitor NF449 completely inhibited BAA-increased cAMP level, prodynorphin expression and antiallodynia, whereas the antagonists of noradrenergic, corticotrophin-releasing factor, A1 adenosine, formyl peptide, D1/D2 dopamine, and glucagon like-peptide-1 receptors failed to block BAA-induced antiallodynia. The data indicate that BAA-induced microglial expression of prodynorphin is mediated by activation of the cAMP-PKA-p38β-CREB signaling pathway, suggesting that its possible target is a Gs-protein-coupled receptor - "aconitine receptor", although the chemical identity is not illustrated.

Efficacy of Japanese traditional (Kampo) medicine for treating chemotherapy-induced peripheral neuropathy: A retrospective case series study

AIM

To investigate Japanese traditional (Kampo) medicine’s effectiveness on cancer chemotherapy-induced peripheral neuropathy (CIPN), we carried out this retrospective study.

METHODS

By searching our outpatient database of 3154 patients who consulted our outpatient clinic of Japanese-Oriental (Kampo) Medicine at Chiba University Hospital from November 2005 to December 2010, a total of 281 patients diagnosed with cancer were identified. Twenty-four patients out of the 281 patients identified met the following three conditions and were eligible for further investigation of the effectiveness of Kampo treatment: At least one course of cancer chemotherapy had been administered; numbness and pain appeared after the chemotherapy; and CIPN was diagnosed before they were given Kampo treatment.

RESULTS

The 24 patients included 6 males and 18 females and ranged in age from 39 to 86 (mean 61.2 ± 11.5) years old. Kampo formulas were individually chosen by Kampo expert doctors based on Kampo-specific diagnostics. Beneficial outcomes were obtained by Kampo treatment in 20 out of the 24 cases (83.3%). Nine out 20 cases had a major response (the numbness and pain showed improvement or reduction by 50% or more), with 7 of 9 cases showing a more than 70% symptom reduction. Eleven out of 20 cases showed a minor response (less than 50% symptom reduction), and 4 out of the 24 cases had no beneficial response. The most frequently used formula was goshajinkigan (GJG), followed by hachimijiogan (HJG) and keishibukuryogan. Thirteen of the 24 cases (54.2%) were prescribed aconite root-containing formulas including GJG and HJG. Aconite root has “warming” effects and ameliorates pain and numbness; 21 out of 24 cases (87.5%) in total used warming formulas such as aconite root-containing formulas to reduce CIPN.

CONCLUSION

Our current study suggested that Kampo formulas chosen based on Kampo-specific diagnostics could be for treating CIPN that is refractory to conventional medicine.

Ester Hydrolysis Differentially Reduces Aconitine-Induced Anti-hypersensitivity and Acute Neurotoxicity: Involvement of Spinal Microglial Dynorphin Expression and Implications for Aconitum Processing

Aconitines, including bulleyaconitine A, probably the most bioactive and abundant alkaloids in Aconitum plant, are a group of diester C19-diterpenoid alkaloids with one acetylester group attached to C8 of the diterpenoid skeleton and one benzoylester group to C14. Hydrolysis of both groups is involved in the processing of Aconitum, a traditional Chinese medicinal approach. We recently demonstrated that bulleyaconitine A produced anti-hypersensitivity, which was mediated by stimulation of spinal microglial dynorphin A expression. This study aimed to elucidate whether the acetylester and benzoylester groups are involved in aconitine-induced dynorphin A expression, anti-hypersensitivity, neurotoxicity in neuropathic rats. Intrathecal administration of aconitine and benzoylaconine (but not aconine) attenuated mechanical allodynia and heat hyperalgesia, with normalized ED₅₀ values of 35 pmol and 3.6 nmol, respectively. Aconitine and benzoylaconine anti-allodynia was completely blocked by the microglial inhibitor, dynorphin A antiserum, and κ-opioid receptor antagonist. Aconitine and benzoylaconine, but not aconine, stimulated dynorphin A expression in cultured primary spinal microglia, with EC₅₀ values of 32 nM and 3 μM, respectively. Intrathecal aconitine, benzoylaconine and aconine induced flaccid paralysis and death, with normalized TD₅₀ values of 0.5 nmol, 0.2 μmol, and 1.6 μmol, respectively. The TD₅₀/ED₅₀ ratios of aconitine and benzolyaconine were 14:1 and 56:1. Our results suggest that both the C8-acetyl and C14-benzoyl groups are essential for aconitine to stimulate spinal microglial dynorphin A expression and subsequent anti-hypersensitivity, which can be separated from neurotoxicity, because both benzoylaconine and aconine differentially produced anti-hypersensitivity and neurotoxicity due to their different stimulatory ability on dynorphin A expression. Our results support the scientific rationale for Aconitum processing, but caution should be taken to avoid overprocessing and excess hydrolysis of benzolyaconine to aconine.

Ignavine: a novel allosteric modulator of the μ opioid receptor

Processed Aconiti tuber (PAT) is used to treat pain associated with various disorders. Although it has been demonstrated that the κ opioid receptor (KOR) signaling pathway is a mediator of the analgesic effect of PAT, active components affecting opioid signaling have not yet been identified. In this study, we explored candidate components of PAT by pharmacokinetic analysis and identified ignavine, which is a different structure from aconitine alkaloids. A receptor binding assay of opioid receptors showed that ignavine specifically binds the μ opioid receptor (MOR), not the KOR. Receptor internalization assay in MOR-expressing cell lines revealed that ignavine augmented the responses produced by D-Ala(2)-N-Me-Phe(4)-Gly-ol(5)-enkephalin (DAMGO), a representative MOR agonist, at a low concentration and inhibited it at a higher concentration. Ignavine also exerted positive modulatory activity for DAMGO, endomorphin-1 and morphine in cAMP assay. Additionally, ignavine alone showed an analgesic effect in vivo. In silico simulation analysis suggested that ignavine would induce a unique structural change distinguished from those induced by a representative MOR agonist and antagonist. These data collectively suggest the possibility that ignavine could be a novel allosteric modulator of the MOR. The present results may open the way for the development of a novel pain management strategy.

Anti-allodynic effect of intrathecal processed Aconitum jaluense is associated with the inhibition of microglial activation and P2X7 receptor expression in spinal cord

Background

For their analgesic and anti-arthritic effects, Aconitum species have been used in folk medicine in some East Asian countries. Although their analgesic effect is attributed to its action on voltage-dependent sodium channels, they also suppress purinergic receptor expression in dorsal root ganglion neurons in rats with neuropathic pain. In vitro study also demonstrated that the Aconitum suppresses ATP-induced P2X7 receptor (P2X7R)-mediated inflammatory responses in microglial cell lines. Herein, we examined the effect of intrathecal administration of thermally processed Aconitum jaluense (PA) on pain behavior, P2X7R expression and microglial activation in a rat spinal nerve ligation (SNL) model.

Methods

Mechanical allodynia induced by L5 SNL in Sprague-Dawley rats was measured using the von Frey test to evaluate the effect of intrathecal injection of PA. Changes in the expression of P2X7R in the spinal cord were examined using RT-PCR and Western blot analysis. In addition, the effect of intrathecal PA on microglial activation was evaluated by immunofluorescence.

Results

Intrathecal PA attenuated mechanical allodynia in a dose-dependent manner showing both acute and chronic effects with 65 % of the maximal possible effect. The expression and production of spinal P2X7R was increased five days after SNL, but daily intrathecal PA injection significantly inhibited the increase to the level of naïve animals. Immunofluorescence of the spinal cord revealed a significant increase in P2X7R expression and activation of microglia in the dorsal horn, which was inhibited by intrathecal PA treatment. P2X7R co-localized with microglia marker, but not neurons.

Conclusions

Intrathecal PA exerts anti-allodynic effects in neuropathic pain, possibly by suppressing P2X7R production and expression as well as reducing microglial activation in the spinal cord.

Processed aconite root and its active ingredient neoline may alleviate oxaliplatin-induced peripheral neuropathic pain

ETHNOPHARMACOLOGICAL RELEVANCE

Processed aconite root (PA, the root of Aconitum carmichaeli, Ranunculaceae) is a crude drug used in traditional Chinese or Japanese kampo medicine to generate heat in the body and to treat pain associated with coldness. Oxaliplatin (L-OHP) is a platinum-based anticancer drug that frequently causes acute and chronic peripheral neuropathies, including cold and mechanical hyperalgesia.

AIM OF THE STUDY

We investigated the effects of PA on L-OHP-induced peripheral neuropathies and identified the active ingredient within PA extract.

MATERIALS AND METHODS

L-OHP was intraperitoneally injected into mice, and PA boiled water extract was orally administered. Cold and mechanical hyperalgesia were evaluated using the acetone test and the von Frey filament method, respectively. Dorsal root ganglion (DRG) neurons were isolated from normal mice and cultured with L-OHP with or without PA extract. Cell viability and neurite elongation were evaluated.

RESULTS

PA extract significantly attenuated cold and mechanical hyperalgesia induced by L-OHP in mice. In cultured DRG neurons, L-OHP reduced cell viability and neurite elongation in a dose-dependent manner. Treatment with PA extract significantly alleviated the L-OHP-induced reduction of neurite elongation, while the cytotoxicity of L-OHP was not affected. Using activity-guided fractionation, we isolated neoline from PA extract as the active ingredient. Neoline significantly alleviated L-OHP-induced reduction of neurite elongation in cultured DRG neurons in a concentration-dependent manner. Moreover, subcutaneous injection of neoline attenuated cold and mechanical hyperalgesia in L-OHP-treated mice. PA extract and neoline did not show sedation and motor impairment.

CONCLUSIONS

The present study indicates that PA and its active ingredient neoline are promising agents to alleviate L-OHP-induced neuropathic pain.

Mother root of Aconitum carmichaelii Debeaux exerts antinociceptive effect in Complet Freund's Adjuvant-induced mice: roles of dynorpin/kappa-opioid system and transient receptor potential vanilloid type-1 ion channel

BACKGROUND

Processed Chuanwu (PCW), the mother root of Aconitum carmichaelii Debeauxv, has been widely used as a classic Traditional Chinese Medicine for pain relieve for over two millennia clinically. However, its action on chronic inflammatory pain has not been clarified. Here, we investigated the antinociceptive effect of PCW in complete freund's adjuvant (CFA)-induced mice and its possible mechanisms associated with opioid system and TRPV1 ion channel.

METHODS

Male ICR mice were intraplantarly injected with CFA. PCW (0.34, 0.68 and 1.35 g/kg) was orally given to mice once a day for 7 days. Von frey hairs and planter test were assessed to evaluate the antinociceptive effect of PCW. To investigate the participation of dynorphin/opioid system in PCW antinociception, subtype-specific opioid receptor antagonists or anti-dynorphin A antiserum were used. To eliminate other central mechanisms that contribute to PCW antinociception, hot plate (50 °C) test were performed. Further, involvements of TRPV1 in PCW antinociception were evaluated in CFA-induced TRPV1(-/-) and TRPV1(+/+) C57BL/6 male mice, and in capsaicin-induced nociception ICR naive mice pretreated with nor-BNI. Meanwhile, calcium imaging was performed in HEK293T-TRPV1 cells. Finally, rotarod, open-field tests and body temperature measurement were carried out to assess side effects of PCW.

RESULTS

PCW dose-dependently attenuated mechanical and heat hypersensitivities with no tolerance, which could be partially attenuated by coadministration of k-opioid receptor antagonist nor-binaltorphimine (nor-BNI) or anti-dynorphin A (1-13) antiserum. And PCW antinociception was totally erased by pretreatment with nor-BNI in the hot plate test. In addition, PCW antinociception was decreased in TRPV1(-/-) mice compared to TRPV1(+/+) group. And PCW still manifested inhibitory effects in capsaicin-induced nociception with nor-BNI pretreatment. PCW significantly inhibited capsaicin-induced calcium influx in HEK293T-TRPV1 cells. Finally, no detectable side effects were found in naive mice treated with PCW.

CONCLUSIONS

This study shows PCW's potent antinociceptive effect in inflammatory conditions without obvious side effects. This effect may result from the activation of κ-opioid receptor via dynorpin release and the inhibition of TRPV1. These findings indicate that PCW might be a potential agent for the management of chronic inflammatory pain.

KCHO-1, a Novel Antineuroinflammatory Agent, Inhibits Lipopolysaccharide-Induced Neuroinflammatory Responses through Nrf2-Mediated Heme Oxygenase-1 Expression in Mouse BV2 Microglia Cells

The brain is vulnerable to oxidative stress and inflammation that can occur as a result of aging or neurodegenerative diseases. Our work has sought to identify natural products that regulate heme oxygenase (HO)-1 and to determine their mechanism of action in neurodegenerative diseases. KCHO-1 is a novel herbal therapeutic containing 30% ethanol (EtOH) extracts from nine plants. In this study, we investigated the antineuroinflammatory effects of KCHO-1 in lipopolysaccharide- (LPS-) treated mouse BV2 microglia. KCHO-1 inhibited the protein expression of inducible nitric oxide synthase (iNOS), iNOS-derived nitric oxide (NO), cyclooxygenase- (COX-) 2, and COX-2-derived prostaglandin E2 (PGE2) in LPS-stimulated BV2 microglia. It also reduced tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and IL-6 production. This effect was correlated with the suppression of inhibitor of nuclear factor kappa B-α (IκB-α) phosphorylation and degradation and nuclear factor kappa B (NF-κB) translocation and DNA binding. Additionally, KCHO-1 upregulated HO-1 expression by promoting nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) in mouse BV2 microglia. Tin protoporphyrin (SnPP), an HO activity inhibitor, was used to verify the inhibitory effects of KCHO-1 on proinflammatory mediators and proteins associated with HO-1 expression. Our data suggest that KCHO-1 has therapeutic potential in neurodegenerative diseases caused by neuroinflammation.

The prophylactic effects of a traditional Japanese medicine, goshajinkigan, on paclitaxel-induced peripheral neuropathy and its mechanism of action

Background

This study aimed to evaluate the prophylactic effect of goshajinkigan (GJG) on paclitaxel (PTX)-induced neuropathy and to elucidate the mechanism of action.

Results

There was a time-dependent irreversible decrease in pain threshold in PTX group. In PTX/GJG group, pain threshold showed changes in the same level as control. Electron microscope showed that although the ganglion cells of control and PTX/GJG groups were normal, degeneration of the nucleus and swelling of the mitochondria were observed in PTX group. Expression of transient receptor potential vanilloid 4 (TRPV4) gene in PTX group significantly increased compared with that in control and PTX/GJG groups. In TRPV4 knock-out mice, no PTX-induced hyperalgesia was observed, and there was no significant difference in pain threshold between the 3 groups.

Conclusions

These results showed that PTX induced hyperalgesia by enhancing TRPV4 expression, and suggested that GJG might alleviate hyperalgesia by preventing degeneration of the ganglion cells and suppressing TRPV4 expression.

Natural products evaluated in neuropathic pain models - a systematic review

Chronic pain conditions, such as neuropathic pain, are a common problem that poses a major challenge to health-care providers due to its complex natural history, unclear aetiology and poor response towards therapy. Despite the large number of drugs available, the adherence is limited by the large range of side effects and pharmacological ineffectiveness. Thus, the search for new chemical entities that can act as promising molecules to treat chronic pain conditions has emerged. The natural products remain as the most promising sources of new chemical entities with applicability for the medical approach. Hence, we performed a systematic review analysing pre-clinical studies shown to be promising in a possible applicability in neuropathic pain. The search terms neuropathic pain, phytotherapy and medicinal plants were used to retrieve English language articles in LILACS, PUBMED and EMBASE published until 10 April 2013. From a total of 1529 articles surveyed, 28 met the inclusion and exclusion criteria established. The main chemical compounds studied were flavonoids (28%), terpenes (17%), alkaloids (14%), phenols (10%), carotenoids (10%) and others (21%). The mostly described animal models for the study of neuropathic pain included were chronic constriction injury (CCI - 32%), partial sciatic nerve ligation (PSNL - 28%), streptozotocin - induced diabetic (28%), alcoholic neuropathy (3.5%), sodium monoiodoacetate (MIA - 3.5%) and neuropathic pain induced by paclitaxel (3.5%). The opioids, serotonergic and cannabinoid systems are suggested as the most promising targets for the natural products described. Therefore, the data reviewed here suggest that these compounds are possible candidates for the treatment of chronic painful conditions, such as neuropathic pain.

Can medical herbs stimulate regeneration or neuroprotection and treat neuropathic pain in chemotherapy-induced peripheral neuropathy?

Chemotherapy-induced neuropathy (CIPN) has a relevant impact on the quality of life of cancer patients. There are no curative conventional treatments, so further options have to be investigated. We conducted a systematic review in English and Chinese language databases to illuminate the role of medical herbs. 26 relevant studies on 5 single herbs, one extract, one receptor-agonist, and 8 combinations of herbs were identified focusing on the single herbs Acorus calamus rhizoma, Cannabis sativa fructus, Chamomilla matricaria, Ginkgo biloba, Salvia officinalis, Sweet bee venom, Fritillaria cirrhosae bulbus, and the herbal combinations Bu Yang Huan Wu, modified Bu Yang Huan Wu plus Liuwei Di Huang, modified Chai Hu Long Gu Mu Li Wan, Geranii herba plus Aconiti lateralis praeparata radix , Niu Che Sen Qi Wan (Goshajinkigan), Gui Zhi Jia Shu Fu Tang (Keishikajutsubuto), Huang Qi Wu Wu Tang (Ogikeishigomotsuto), and Shao Yao Gan Cao Tang (Shakuyakukanzoto). The knowledge of mechanism of action is still limited, the quality of clinical trials needs further improvement, and studies have not yielded enough evidence to establish a standard practice, but a lot of promising substances have been identified. While CIPN has multiple mechanisms of neuronal degeneration, a combination of herbs or substances might deal with multiple targets for the aim of neuroprotection or neuroregeneration in CIPN.

Synergistic interaction between total glucosides and total flavonoids on chronic constriction injury induced neuropathic pain in rats

CONTEXT

Shaoyao Gancao Decoction (SGD), a famous herbal medicine, consists of two herbs (Paeoniae Radix and Glycyrrhizae Radix) and is traditionally used for the treatment of pain.

OBJECTIVE

To investigate the synergistic potential of total glucosides of Paeoniae Radix (TGP) and total flavonoids of Glycyrrhizae Radix (TFL).

MATERIALS AND METHODS

Oral administration of TGP and TFL alone at the doses of 60,120 and 240 mg/kg or in combination were given only one time to the neuropathic pain rat induced by chronic constriction injury. Paw pressure and heat immersion tests were performed to assess degrees of mechanical allodynia and thermal hyperalgesia, respectively. Synergistic interactions between TGP and TFL were characterized using isobolographic analysis. Expressions of Sirt1 protein were detected by immunohistochemistry.

RESULTS AND DISCUSSION

On day 14 after surgery, single oral administration of TGP and TFL both produced significant anti-allodynic and anti-hyperalgesic effects in dose-dependent and time-dependent manners. The ED(50) value of TGP was 249.4 ± 10.8 mg/kg while TFL was 871.4 ± 30.5 mg/kg. Isobolographic analysis revealed that the combination of TGP with TFL at the fixed ratios of 3:1 exerted the highest sub-additive (synergistic) interaction, of which the experimental ED(50) value was 95.1 ± 9.0 mg/kg. SGD could also downregulate Sirt1 protein expression, which was 4.2-fold higher than that of model rats in dorsal root ganglion.

CONCLUSION

Analgesic effects of SGD may contribute to simultaneous inhibition of Sirt1 overexpression and could warrant further evaluation as a possible agent for the treatment of neuropathic pain.

Efficacy of traditional Japanese herbal medicines-Keishikajutsubuto (TJ-18) and Bushi-matsu (TJ-3022)-against postherpetic neuralgia aggravated by self-reported cold stimulation: a case series

OBJECTIVES

It has been reported that postherpetic neuralgia (PHN) in patients over 60 years of age is aggravated under cold stimulation and is often difficult to treat. Keishikajutsubuto (TJ-18) and Bushi-matsu (TJ-3022) are traditional Japanese herbal medicines and have long been used to treat neuralgia and arthralgia, which are aggravated following cold stimulation. This study was designed to evaluate the effectiveness of combined TJ-18 and TJ-3022 therapy in cases of PHN aggravated by self-reported cold stimulation.

DESIGN

Fifteen (15) PHN patients aged 60 years and over were examined. Patients were aware of the persistent pain despite other treatments; pain was generally aggravated following exposure to cold stimulation. First, TJ-18 (7.5 g/day) was administered to patients, and then TJ-3022 (1.0 g/day) was also administered and progressively increased by 0.5-1.0 g increments every 2-4 weeks, until stable improvement was achieved, which was rated using the visual analogue scale (VAS). Analgesic effects were evaluated using the VAS during each patient visit.

OUTCOME MEASURES

Background variables, responses to treatment (time course of VAS rating, VAS improvement rate), the amount of additional TJ-3022 administered, and adverse reactions were analyzed.

RESULTS

Twelve (12) of the 15 patients completed the entire trial. Patient ages were 61-85 years, the male-to-female ratio was 4:8, and length of time after onset of herpes zoster was 2-92 months. In 3 patients, oral TJ-18 treatment was not possible due to hot flash or gastric discomfort. The VAS improvement rate for patients being orally administered both TJ-18 and TJ-3022 was 76.5±27.7% (mean±standard deviation). The additional TJ-3022 dose was 1.0-5.0 g/day. Twelve (12) patients have been treated without serious adverse reactions.

CONCLUSIONS

TJ-18 and TJ-3022 combination treatment is a promising means of treating intractable PHN, which has a self-reported tendency to aggravate pain under cold stimulation.

Treatment of neuropathic pain with plant medicines

Neuropathic pain is a common and very prevalent disorder affecting the citizens of both developed and developing countries. The approved and licensed drugs for neuropathic pain are reported to have associated side effects. Traditional plant treatments have been used throughout the world for the treatment of neuropathic pain. Among the many medications and other alternative medicines, several herbs are known to cure and control neuropathic pain with no side effects. The present paper discusses the plants with neuropathic pain and related beneficial effects originating from different parts of world that are of current interest.

Inhibitory effects of processed Aconiti tuber on morphine-induced conditioned place preference in rats

AIM OF THE STUDY

Our previous studies indicated that processed Aconiti tuber (PAT), a traditional Chinese herbal medicine, had antinociceptive effects and inhibitory effects on morphine tolerance by activation of kappa-opioid receptor (KOR). Preclinical studies also demonstrated that KOR agonists functionally attenuate addictive behaviors of morphine, such as conditioned place preference (CPP). Therefore, we hypothesize that PAT may inhibit morphine-induced CPP in rats.

MATERIALS AND METHODS

(1) Five groups of rats (n=8 for each group) were alternately subcutaneous (s.c.) injected with morphine 10mg/kg (one group receive normal saline as a control) and normal saline for 8 days and oral co-administrated with distilled water or PAT 0.3, 1.0, or 3.0 g/kg daily on days 2-9 during CPP training, respectively. (2) Other four groups of rats were randomly s.c. injected with nor-binaltorphimine (nor-BNI; 5mg/kg) or normal saline (as a control) 120 min before alternately s.c. with morphine and normal saline and oral co-administrated with distilled water or PAT 3.0 g/kg daily. Each rat was acquired pre-conditioning and post-conditioning CPP data and assayed dynorphin concentrations by radioimmunoassay in rat's nucleus accumbens (NAc) after CPP training.

RESULTS

(1) PAT 1.0 or 3.0 g/kg dose-dependently decreased the morphine-induced increase of CPP scores. (2) Nor-BNI completely antagonized the inhibition of PAT on morphine-induced CPP. (3) PAT dose-dependently increased dynorphin content in rats' NAc after CPP training.

CONCLUSIONS

(1) PAT dose-dependently inhibited morphine-induced CPP. (2) The inhibition of PAT on morphine-induced CPP was probably due to activation of KOR by increasing dynorphin release in rats' NAc.

Anti-hypersensitivity effects of Shu-jing-huo-xue-tang, a Chinese herbal medicine, in CCI-neuropathic rats

AIM OF THE STUDY

Shu-jing-huo-xue-tang (SJHXT) (Japanese name: Sokei-kakketu-to), a traditional Chinese herbal medicine composed of 17 crude drugs, has been prescribed over hundreds of years for treatment of chronic pain syndromes. We evaluated if oral SJHXT could suppress neuropathic pain behaviors in rats with chronic constriction injury (CCI) of the sciatic nerve.

MATERIALS AND METHODS

(1) Rats received repeated oral SJHXT 0.5 or 1.0 g/kg once daily for 14 days starting 24 h after CCI surgery, while neuropathic manifestations were evaluated until day 20 post-CCI. (2) Other groups of rats received single oral SJHXT 1.0 g/kg on day 14 post-CCI. (3) Additional groups of rats received oral SJHXT 1.0 g/kg on day 14 post-CCI, concomitantly with intraperitoneal yohimbine 1 mg/kg or methysergide 5 mg/kg. Neuropathic manifestations, including mechanical allodynia and thermal hyperalgesia, were evaluated with paw withdrawal responses to increasing mechanical pressure and radiant heat, respectively.

RESULTS

Mechanical allodynia and thermal hyperalgesia developed by day 14 post-CCI. Repeated oral SJHXT for 14 days produced anti-allodynic and anti-hyperalgesic effects that outlasted the period of drug administration. Single oral SJHXT on day 14 also produced significant anti-allodynic and anti-hyperalgesic effects, which were inhibited by yohimbine, an alpha-2 adrenoceptor antagonist, but not by methysergide, a serotonin receptor antagonist.

CONCLUSIONS

Oral SJHXT produced anti-hypersensitivity effects by actions on alpha-2 adrenoreceptors in CCI-neuropathic rats, and chronic oral administration of SJHXT could produce the long-lasting anti-hypersensitivity effects.

High doses of processed Aconiti tuber inhibit the acute but potentiate the chronic antinociception of morphine

AIM OF THE STUDY

In this study, we investigated the effects of processed Aconiti tuber (PAT), an oriental herbal medicine, at analgesic doses on acute morphine antinociception in morphine-naïve mice and morphine tolerance in morphine-tolerant mice.

MATERIALS AND METHODS

In acute experiments, mice received subcutaneous (s.c.) morphine (2, 5, or 10 mg/kg) and oral distilled water or PAT (0.3, 1.0, or 3.0 g/kg). The mechanical nociceptive threshold (MNT) and thermal nociceptive latency (TNL) were measured with the tail pressure test and tail flick test, respectively, before, and at 30, 60, 90, and 120 min after s.c. morphine injection. In chronic experiments, mice received s.c. morphine (10 mg/kg) and oral distilled water or PAT (0.3, 1.0, or 3.0 g/kg) once daily for 11 days. MNT was measured before, and at 60 min after, and TNL was measured before, and at 30 min after, daily morphine injections on days 1-11.

RESULTS

PAT at analgesic doses inhibited the acute antinociceptive effect of morphine dose-dependently in morphine-naïve mice. In contrast, PAT at analgesic doses potentiated the chronic antinociceptive effect of morphine dose-dependently by inhibiting the development of morphine tolerance dose-dependently. These effects of PAT on acute and chronic morphine antinociception were mediated through activation of kappa-opioid receptors.

CONCLUSIONS

These results indicated that chronic co-administration of PAT at analgesic doses with morphine could provide better-maintained morphine analgesia in a long-term morphine treatment after initial inhibition of acute morphine antinociception for a brief period of time.

The comparison of effects of processed Aconiti tuber, U50488H and MK-801 on the antinociceptive tolerance to morphine

In the previous studies, we demonstrated that an oriental herbal medicine, processed Aconiti tuber (PAT), at subanalgesic doses could inhibit or reverse the antinociceptive tolerance to morphine. In the present study, we compared the effect of PAT, trans-(+/-)-3,4-dichloro-N-methyl-N-(2-(1-pyrrolidin)cyclohexyl)-benzeneacetamide methane sulfonate hydrate (U50488H), a selective kappa opioid receptor (KOR) agonist, and (-)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine-maleate (MK-801), a N-methyl-D-aspartate (NMDA) receptor antagonist, on the antinociceptive tolerance to morphine in the same experimental condition. Mice received subcutaneous morphine (10 mg/kg), and oral PAT at a subanalgesic dose (0.3 g/kg for mechanical or 1.0 g/kg for thermal test), or intraperitoneal U50488H at a subanalgesic dose (3 mg/kg), or MK-801 at a subanalgesic dose (0.1 mg/kg) once daily for 14 days. The mechanical nociceptive threshold was measured before, and at 60 min by tail pressure testing, and thermal nociceptive latency was measured before, and at 30 min by hot plate testing, after daily morphine injections. PAT and U50488H could not only inhibit the development of morphine tolerance but also reverse the already-developed morphine tolerance, while MK-801 could only inhibit the development of morphine tolerance but not reverse the already-developed morphine tolerance, in both mechanical and thermal nociceptive tests. These data suggested that PAT, an indirect-acting KOR agonist, share the common pharmacological property of KOR agonists on morphine tolerance, and that PAT may be superior to some NMDA receptor antagonists which do not reverse already-developed morphine tolerance.

Characterization of aconitine-induced block of delayed rectifier K+ current in differentiated NG108-15 neuronal cells

The effects of aconitine (ACO), a highly toxic alkaloid, on ion currents in differentiated NG108-15 neuronal cells were investigated in this study. ACO (0.3-30 microM) suppressed the amplitude of delayed rectifier K+ current (I K(DR)) in a concentration-dependent manner with an IC50 value of 3.1 microM. The presence of ACO enhanced the rate and extent of I K(DR) inactivation, although it had no effect on the initial activation phase of I K(DR). It could shift the inactivation curve of I K(DR) to a hyperpolarized potential with no change in the slope factor. Cumulative inactivation for I K(DR) was also enhanced by ACO. Orphenadrine (30 microM) or methyllycaconitine (30 microM) slightly suppressed I K(DR) without modifying current decay. ACO (10 microM) had an inhibitory effect on voltage-dependent Na+ current (I Na). Under current-clamp recordings, ACO increased the firing and widening of action potentials in these cells. With the aid of the minimal binding scheme, the ACO actions on I K(DR) was quantitatively provided with a dissociation constant of 0.6 microM. A modeled cell was designed to duplicate its inhibitory effect on spontaneous pacemaking. ACO also blocked I K(DR) in neuroblastoma SH-SY5Y cells. Taken together, the experimental data and simulations show that ACO can block delayed rectifier K+ channels of neurons in a concentration- and state-dependent manner. Changes in action potentials induced by ACO in neurons in vivo can be explained mainly by its blocking actions on I K(DR) and I Na.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 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 neurological 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 and thermoregulation (Section 16); and immunological responses (Section 17).

Inhibitory effect of processed Aconiti tuber on the development of antinociceptive tolerance to morphine: evaluation with a thermal assay

In the previous studies, we demonstrated that an oriental herbal medicine processed Aconiti tuber (PAT) at subanalgesic doses could inhibit the development of mechanical antinociceptive tolerance to morphine using the tail pressure test. In the present study, we evaluated whether PAT could inhibit thermal antinociceptive tolerance to morphine using the high temperature (55 degrees C) hot plate test. Mice received subcutaneous morphine (10mg/kg), and oral PAT at doses that did not inhibit the hot plate response (0.3, 0.5, 1.0, and 2.0 g/kg), once daily for 14 days. The thermal nociceptive latency was measured at 30 min after daily morphine injections. Compared with placebo, oral PAT partially and dose-dependently inhibited the development of morphine tolerance in morphine-naïve mice, and reversed already-developed morphine tolerance in morphine-tolerant mice. These data suggested that PAT at subanalgesic doses could dose-dependently inhibit and reverse thermal antinociceptive tolerance to morphine.

Inhibition of morphine tolerance by processed Aconiti tuber is mediated by kappa-opioid receptors

Previously, we found that processed Aconiti tuber (PAT) could inhibit morphine tolerance in mice. In the present study, we investigated mechanisms underlying this effect. Mice received subcutaneous (s.c.) morphine (10 mg/kg) and oral PAT at a subanalgesic dose (0.3 g/kg), once a day for 12 days. Additional PAT-treated groups received morphine and PAT, at 120 min after pretreatment with s.c. clocinnamox mesylate (C-CAM) (0.5 mg/kg), or nor-binaltorphimine (nor-BNI) (5 mg/kg). The antinociceptive effect was assessed with the tail pressure test, at 60 min after the daily s.c. morphine injections were given. In the placebo-treated group, repeated morphine injections caused morphine tolerance, and morphine antinociception was abolished by day 6, whereas in PAT-treated groups, significant antinociception was maintained until day 12, suggesting that PAT inhibited morphine tolerance, thereby sustaining morphine antinociception. C-CAM, a selective mu-opioid receptor (MOR) antagonist, blocked morphine antinociception whereas nor-BNI, a selective kappa-opioid receptor (KOR) antagonist, did not. However, both C-CAM and nor-BNI could block the antinociception maintained by the morphine-PAT combination. Results of the study suggested that chronic treatment with PAT at a subanalgesic dose maintained MOR-mediated morphine antinociception by attenuating development of morphine tolerance, and that this tolerance-attenuating effect of PAT was mediated by KOR.

Effects of processed Aconiti tuber and its ingredient alkaloids on the development of antinociceptive tolerance to morphine

Processed Aconiti tuber (PAT) is a herbal medicine that has been widely used as an analgesic since ancient times. We investigated effects of subanalgesic doses of PAT on morphine tolerance in mice. Mice received subcutaneous morphine (10 mg/kg) and oral PAT at subanalgesic doses (0.1 or 0.3 g/kg), once a day for 7 days. Mechanical nociceptive thresholds were measured using the tail pressure test, at 60 min after the daily s.c. morphine injections. In the placebo-treated group, repeated administration of s.c. morphine resulted in development of analgesic tolerance. In the PAT-treated groups, oral PAT attenuated morphine tolerance, dose-dependently. The main ingredient alkaloid of PAT causing its tolerance-attenuating activity was mesaconitine, but other ingredient alkaloids, such as aconitine and hypaconitine, also contributed to this activity. In addition, repeated treatment with PAT could reverse already-developed morphine tolerance. Subanalgesic doses of oral PAT thus can attenuate and reverse morphine tolerance in mice.