Oral acute toxicity study and in vivo antimalarial activity of Strychnos lucida R. Br. tablet.

ETHNOPHARMACOLOGICAL RELEVANCE: Malaria eradication has been a major goal of the Indonesian government since 2020. Medicinal plants, such as Strychnos lucida R. Br., are empirically used to treat malaria through traditional preparation methods. However, the safety and efficacy of these plants have not yet been confirmed. Therefore, further investigations are necessary to confirm the safety and efficacy of S. lucida as an antimalarial agent. AIMS OF THE STUDY: To quantify the concentration of brucine in the S. lucida extract, determine the acute oral toxicity of the standardized extract, and evaluate the in vivo antimalarial potency of S. lucida tablet (SLT). MATERIALS AND METHODS: Acute oral toxicity of S.lucida extract was determined using the Organization for Economic Co-operation and Development 420 procedure, and the analytical method for brucine quantification was validated using high-performance liquid chromatography. In addition, antimalarial activity was determined using the Peter's four-day suppressive method. RESULTS: Acute toxicity analysis revealed S. lucida as a low-toxicity compound with a cut-off median lethal dose of 2000-5000 mg/kg body weight [BW], which was supported by the hematological and biochemical profiles of the kidneys, liver, and pancreas (p > 0.05). Extract standardization revealed that S. lucida contained 3.91 ± 0.074% w/w brucine, adhering to the limit specified in the Indonesian Herbal Pharmacopeia. Antimalarial test revealed that SLT inhibited the growth of Plasmodium berghei by 27.74-45.27%. Moreover, SLT improved the hemoglobin and hematocrit levels. White blood cell and lymphocyte counts were lower in the SLT-treated group than in the K (+) group (p < 0.05). CONCLUSION: Histopathological and biochemical evaluations revealed that S. lucida extract was safe at a dose of 2000 mg/kg BW with low toxicity. SLT inhibited Plasmodium growth and improved the hemoglobin, hematocrit, and red blood cell profiles. Additionally, SLT reduced the lymphocyte and WBC counts and increased the monocyte and thrombocyte counts as part of the immune system response against Plasmodium infection.

A Combination of In Silico ADMET Prediction, In Vivo Toxicity Evaluation, and Potential Mechanism Exploration of Brucine and Brucine N-oxide-A Comparative Study.

Brucine (BRU) and brucine N-oxide (BNO) are prominent, bioactive, and toxic alkaloids in crude and processed Semen Strychni. Studies have demonstrated that BRU and BNO possess comprehensive pharmacological activities, such as anti-inflammatory and analgesic. In this context, a comparative study of BRU and BNO was performed by combination analysis of in silico ADMET prediction, in vivo toxicity evaluation, and potential action mechanism exploration. ADMET prediction showed that BRU and BNO might induce liver injury, and BRU may have a stronger hepatoxic effect. The prediction was experimentally verified using the zebrafish model. The BRU-induced hepatotoxicity of zebrafish larvae had a dose-response relationship. The mechanism of BRU-induced hepatotoxicity might relate to phosphorylation, kinase activity, and signal transduction. By comparison, signal transduction and gap junctions might involve BNO-induced hepatotoxicity. Our results provided a better understanding of BRU- and BNO-induced hepatotoxicity. We also built a foundation to elucidate the material base of the hepatotoxicity of traditional Chinese medicine Semen Strychni.

Network toxicology and molecular docking analyses on strychnine indicate CHRM1 is a potential neurotoxic target.

BACKGROUND: Improper use of strychnine can cause death. The aim of this study was to identify and evaluate toxic mechanisms of action associated with active compounds in strychnine using a network toxicology approach, and explore potential pathogenic targets. METHODS: In the present study, strychnine target and central nervous system-related gene set were established using the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database and four disease gene databases (Genecards, OMIM, PharmGkb, TTD). An "ingredient-target" interactive active network map was constructed using Cytoscape software (version 3.8.0). Functional enrichment analysis was performed based on the hub genes. A protein-protein interaction network was constructed using STRING database. The pharmacokinetics (ADMET) properties of strychnine were evaluated using SwissADME tool. Molecular docking was performed using Autodock Vina to explore the interactions between the active compounds and the target protein. RESULTS: Five strychnine toxicity-related components and a gene set of 40 genes were obtained. GO and KEGG analyses showed that Strychnine acts on the central nervous system through G protein-coupled receptor signaling pathway. Analysis of "ADMET" related parameters showed a high gastrointestinal tract absorption of (S)-stylopine and isobrucine and the compounds could cross the blood brain barrier. CHRM1 was selected as a key gene in strychnine toxicity. Molecular docking results showed that the co-crystalized ligands did not form hydrogen bond with CHRM1. (S)-stylopine had the highest binding affinity (binding energy = - 8.5 kcal/mol) compared with the other two compounds. CONCLUSION: Network toxicology and molecular docking reveal the toxicity mechanisms of strychnine active compounds. The findings showed that CHRM1 is a potential neurotoxic target. (S)-stylopine showed stronger neurotoxic effect compared with the other ligands.

The Anticonvulsant Effect of Hydroethanolic Leaf Extract of Calotropis procera (Ait) R. Br. (Apocynaceae).

A number of currently used drugs have been obtained from medicinal plants which are a major source of drugs. These drugs are either used in their pure form or modified to a semisynthetic drug. Drug discovery through natural product research has been fruitful over the years. Traditionally, Calotropis procera is used extensively in the management of epilepsy. This study is conducted to explore the anticonvulsant effect of a hydroethanolic leaf extract of Calotropis procera (CPE) in murine models. This effect was evaluated using picrotoxin-induced convulsions, strychnine-induced convulsions, and isoniazid- and pilocarpine-induced status epilepticus in mice of both sexes. The results showed that CPE (100-300 mg/kg) exhibited an anticonvulsant effect against strychnine-induced clonic seizures by significantly reducing the duration (p = 0.0068) and frequency (p = 0.0016) of convulsions. The extract (100-300 mg/kg) caused a profound dose-dependent delay in the onset of clonic convulsions induced by picrotoxin (p < 0.0001) and tonic convulsions (p < 0.0001) in mice. The duration of convulsions was reduced significantly also for both clonic and tonic (p < 0.0001) seizures as well. CPE (100-300 mg/kg), showed a profound anticonvulsant effect and reduced mortality in the pilocarpine-induced convulsions. ED50 (~0.1007) determined demonstrated that the extract was less potent than diazepam in reducing the duration and onset of convulsions but had comparable efficacies. Flumazenil-a GABAA receptor antagonist-did not reverse the onset or duration of convulsions produced by the extract in the picrotoxin-induced seizure model. In isoniazid-induced seizure, CPE (300 mg kg1, p.o.) significantly (p < 0.001) delayed the onset of seizure in mice and prolonged latency to death in animals. Overall, the hydroethanolic leaf extract of Calotropis procera possesses anticonvulsant properties.

Chronotoxicity of Semen Strychni is associated with circadian metabolism and transport in mice.

OBJECTIVES: We aimed to determine the circadian responses of mice to Semen Strychni and to investigate the role of pharmacokinetics in generating chronotoxicity. METHODS: Total extract of Semen Strychni was administered by oral gavage to wild-type (WT) and Bmal1-/- (a circadian clock-deficient model) mice at different circadian time points for toxicity (including survival) and pharmacokinetic characterization. Nephrotoxicity and neurotoxicity were evaluated by measuring plasma creatinine and creatine kinase BB (CK-BB), respectively. Drug metabolism and transport assays were performed using liver/intestine microsomes and everted gut sacs, respectively. KEY FINDINGS: Semen Strychni nephrotoxicity and neurotoxicity as well as animal survival displayed significant circadian rhythms (the highest level of toxicity was observed at ZT18 and the lowest level at ZT2 to ZT6). According to pharmacokinetic experiments, herb dosing at ZT18 generated higher plasma concentrations (and systemic exposure) of strychnine and brucine (two toxic constituents) compared with ZT6 dosing. This was accompanied by reduced formation of both dihydroxystrychnine and strychnine glucuronide (two strychnine metabolites) at ZT18. Bmal1 ablation sensitized mice to Semen Strychni-induced toxicity (with increased levels of plasma creatinine and CK-BB) and abolished the time dependency of toxicity. Metabolism of Semen Strychni (strychnine and brucine) in the liver and intestine microsomes of WT mice was more extensive at ZT6 than at ZT18. These time differences in hepatic and intestinal metabolism were lost in Bmal1-/- mice. Additionally, the intestinal efflux transport of Semen Strychni (strychnine and brucine) was more extensive at ZT6 than ZT18 in WT mice. However, the time-varying transport difference was abolished in Bmal1-/- mice. CONCLUSIONS: Circadian responses of mice to Semen Strychni are associated with time-varying efflux transport and metabolism regulated by the circadian clock (Bmal1). Our findings may have implications for optimizing phytotherapy with Semen Strychni via timed delivery.

Anticonvulsant effects of the aqueous and methanol extracts from the stem bark of Psychotria camptopus Verdc. (Rubiacaea) in rats.

ETHNOPHARMACOLOGY RELEVANCE: The decoction from the stem bark of Psychotria camptopus (Rubiaceae) is used in the Cameroonian pharmacopoeia to treat neurological pathologies including epilepsy. AIM: The present work was undertaken to study the anticonvulsant properties of the aqueous (AE) and methanol (ME) extracts from the stem bark of P. camptopus in acute models of epileptic seizures in Wistar rats. METHOD: AE and ME were obtained by decoction and maceration of the stem bark powder in water and methanol, respectively. They were tested orally at the doses of 40, 80 and 120 mg/kg, on the latency of onset and duration of epileptic seizures induced by pentylene tetrazole (PTZ, 70 mg/kg, i.p.). The kinetic effect of both extracts at 120 mg/kg was evaluated. Their effects on diazepam (50 mg/kg) induced sleep and strychnine (STR, 2.5 mg/kg, i.p.) induced seizures were determined. ME was further tested on picrotoxin (PIC, 7.5 mg/kg, i.p.) and thiosemicarbazide (TSC, 50 mg/kg, i.p.) induced seizure models. The phytochemical composition of ME was assessed using LC-MS method, as well as its acute toxicity. RESULTS: AE and ME significantly (p < 0.001) reduced the duration of seizures in both PTZ and STR models. Their maximal effect was observed at 1 h after administration, though their effect at 120 mg/kg was maintained (p < 0.05) up to 24 h post-treatment. Both extracts significantly (p < 0.01) reduced sleep duration. ME significantly (p < 0.001) increased the latency of rat death on PIC-induced convulsions. In TSC rats, ME significantly (p < 0.001) delayed the latency to the first convulsion, and decreased the duration and frequency of convulsions. ME showed no acute toxicity while its phytochemical screening revealed the presence of two flavonoids (Rutin and Butin), two triterpenoid saponins (Psycotrianoside B and Bauerenone) and four alkaloids (10-Hydroxy-antirhine, 10-hydroxy-iso-deppeaninol, Emetine and Hodkinsine). In conclusion, AE and ME from the stem bark of P. camptopus have comparable anticonvulsant properties. The effect of ME is likely due to the presence of flavonoids and alkaloid and the activation of GABA pathway. These results further justify and support the use of P. camptopus in traditional medicine for the treatment of epilepsy.

Cyp3a11 metabolism-based chronotoxicity of brucine in mice.

Brucine is one of the main bioactive and toxic constituents of the herb drug Semen Strychni. Here we aimed to determine dosing time-dependent hepatotoxicity of brucine, and to investigate the role of metabolism in generation of brucine chronotoxicity. Brucine was administered to wild-type or Npas2-/- (a clock disrupted model) mice at different circadian time points for toxicity and pharmacokinetic characterization. The hepatotoxicity was evaluated by plasma alanine aminotransferase and aspartate aminotransferase measurements and histopathological analysis. The role of Cyp3a11 in brucine metabolism was determined by chemical inhibition assays and Cyp3a11-overexpressing HEK293 cells. Hepatic circadian Cyp3a11 mRNA and protein levels were determined by qPCR and Western blotting, respectively. The toxicity of brucine was more severe in the light phase [Zeitgeber time (ZT) 2 and ZT8] than in the dark phase (ZT14 and ZT20). Chemical inhibition and substrate metabolism assays suggested Cyp3a11 as a significant contributor to brucine metabolism. The Cyp3a11 mRNA, protein and activity in the livers of wild-type mice displayed significant circadian fluctuations. Npas2 ablation markedly down-regulated Cyp3a11 mRNA, protein and activity, and abrogated their circadian rhythms. The circadian time differences in brucine pharmacokinetics and liver distribution were lost in Npas2-/- mice, so were the time differences in brucine hepatotoxicity. In conclusion, chronotoxicity of brucine was determined by circadian variations in Cyp3a11 metabolism. The findings have implications in improving brucine (and possibly Semen Strychni) efficacy via dosing time optimization.

Neurochemical effects of motor cortex stimulation in the periaqueductal gray during neuropathic pain.

OBJECTIVE: Motor cortex stimulation (MCS) is a neurosurgical technique used to treat patients with refractory neuropathic pain syndromes. MCS activates the periaqueductal gray (PAG) matter, which is one of the major centers of the descending pain inhibitory system. However, the neurochemical mechanisms in the PAG that underlie the analgesic effect of MCS have not yet been described. The main goal of this study was to investigate the neurochemical mechanisms involved in the analgesic effect induced by MCS in neuropathic pain. Specifically, we investigated the release of γ-aminobutyric acid (GABA), glycine, and glutamate in the PAG and performed pharmacological antagonism experiments to validate of our findings. METHODS: Male Wistar rats with surgically induced chronic constriction of the sciatic nerve, along with sham-operated rats and naive rats, were implanted with both unilateral transdural electrodes in the motor cortex and a microdialysis guide cannula in the PAG and subjected to MCS. The MCS was delivered in single 15-minute sessions. Neurotransmitter release was evaluated in the PAG before, during, and after MCS. Quantification of the neurotransmitters GABA, glycine, and glutamate was performed using a high-performance liquid chromatography system. The mechanical nociceptive threshold was evaluated initially, on the 14th day following the surgery, and during the MCS. In another group of neuropathic rats, once the analgesic effect after MCS was confirmed by the mechanical nociceptive test, rats were microinjected with saline or a glycine antagonist (strychnine), a GABA antagonist (bicuculline), or a combination of glycine and GABA antagonists (strychnine+bicuculline) and reevaluated for the mechanical nociceptive threshold during MCS. RESULTS: MCS reversed the hyperalgesia induced by peripheral neuropathy in the rats with chronic sciatic nerve constriction and induced a significant increase in the glycine and GABA levels in the PAG in comparison with the naive and sham-treated rats. The glutamate levels remained stable under all conditions. The antagonism of glycine, GABA, and the combination of glycine and GABA reversed the MCS-induced analgesia. CONCLUSIONS: These results suggest that the neurotransmitters glycine and GABA released in the PAG may be involved in the analgesia induced by cortical stimulation in animals with neuropathic pain. Further investigation of the mechanisms involved in MCS-induced analgesia may contribute to clinical improvements for the treatment of persistent neuropathic pain syndromes.

High-Throughput Electrophysiology Screen Revealed Cardiotoxicity of Strychnine by Selectively Targeting hERG Channel.

Although the efficacy and the health care advantages of Chinese herbal medicine (CHM) have become increasingly recognized worldwide, the potential side effects and toxicity still restrict its broader application. This study established and applied an integrated platform anchored on automatic patch clamp system to screen and evaluate a collection of CHM extracts, compositions and monomeric compounds for in vitro cardiac toxicity. Of 1036 CHM samples screened, 2.79% significantly inhibited hERG channel activity. Among them, Strychnine was identified for the first time as a potent hERG inhibitor with an IC 50 of 6.65±1.04µ M in comparison to that of Dofetilide at 1.80±0.24µ M and Quinidine at 7.42±0.54µ M. Langendorff-perfusion experiments confirmed that strychnine increased QT interphase from 71.69±5.34 ms to 98.61±5.54 ms and decreased heart rates from 227.65±5.40 bmp to 162.91±14.70 bmp in isolated rat hearts. The cardiac toxicity effect of strychnine appears to be specific to hERG channel since an in vitro multiplex imaging analysis showed that it did not affect cellular phenotypes such as cell vitality, nucleus area, mitochondria mass and function, nor intracellular calcium in rat primary myocytes. This integrated high-throughput hERG patch clamp and high-content multi-parameter imaging cardiac toxicity screen approach should be useful for large-scale preclinical evaluation of complex Chinese herbal medicine.

Prophylactic Neuroprotection of Total Glucosides of Paeoniae Radix Alba against Semen Strychni-Induced Neurotoxicity in Rats: Suppressing Oxidative Stress and Reducing the Absorption of Toxic Components.

Strychnos alkaloids (SAs) are the main toxic constituents in Semen Strychni, a traditional Chinese medicine, which is known for its fatal neurotoxicity. Hence, the present study was carried out to evaluate the neurotoxicity induced by SAs and the pre-protective effects of the total glucosides of Paeoniae Radix Alba (TGP). An SA brain damage model was firstly established. The neurotoxicity induced by SAs and the pre-protective effects of TGP were confirmed by physical and behavioral testing, biochemical assay, and histological examination. Then, a liquid chromatography-tandem mass spectrometry method was developed and validated to investigate the time-course change and distribution of strychnine and brucine (two main SAs) in the brain after oral SA administration with or without TGP pretreatment. Biochemical analysis results indicated that TGP could ameliorate the oxidative stress status caused by SAs. Time-course change and distribution studies demonstrated that strychnine and brucine were rapidly absorbed into the brain, peaked early at 0.5 h, and were mainly located in the hippocampus and cerebellum. TGP showed a pre-protective effect against neurotoxicity by reducing the absorption of toxic alkaloids into the brain. These findings could provide beneficial information in facilitating future studies of Semen Strychni neurotoxicity and developing herbal medicines to alleviate neurotoxicity in the clinic.

Involvement of glycine receptor α1 subunits in cannabinoid-induced analgesia.

Some cannabinoids have been shown to suppress chronic pain by targeting glycine receptors (GlyRs). Although cannabinoid potentiation of α3 GlyRs is thought to contribute to cannabinoid-induced analgesia, the role of cannabinoid potentiation of α1 GlyRs in cannabinoid suppression of chronic pain remains unclear. Here we report that dehydroxylcannabidiol (DH-CBD), a nonpsychoactive cannabinoid, significantly suppresses chronic inflammatory pain caused by noxious heat stimulation. This effect may involve spinal α1 GlyRs since the expression level of α1 subunits in the spinal cord is positively correlated with CFA-induced inflammatory pain and the GlyRs antagonist strychnine blocks the DH-CBD-induced analgesia. A point-mutation of S296A in TM3 of α1 GlyRs significantly inhibits DH-CBD potentiation of glycine currents (IGly) in HEK-293 cells and neurons in lamina I-II of spinal cord slices. To explore the in vivo consequence of DH-CBD potentiation of α1 GlyRs, we generated a GlyRα1S296A knock-in mouse line. We observed that DH-CBD-induced potentiation of IGly and analgesia for inflammatory pain was absent in GlyRα1S296A knock-in mice. These findings suggest that spinal α1 GlyR is a potential target for cannabinoid analgesia in chronic inflammatory pain.

Botany, Phytochemistry, Pharmacology and Toxicity of Strychnos nux-vomica L.: A Review.

Strychnos nux-vomica L. belongs to the genus Strychnos of the family Loganiaceae and grows in Sri Lanka, India and Australia. The traditional medicinal component is its seed, called Nux vomica. This study provides a relevant and comprehensive review of S. nux-vomica L., including its botany, ethnopharmacology, phytochemistry, pharmacology and toxicology, thus providing a foundation for future studies. Up to the present day, over 84 compounds, including alkaloids, iridoid glycosides, flavonoid glycosides, triterpenoids, steroids and organic acids, among others, have been isolated and identified from S. nux-vomica. These compounds possess an array of biological activities, including effects on the nervous system, analgesic and anti-inflammatory actions, antitumor effects, inhibition of the growth of pathogenic microorganisms and regulation of immune function. Furthermore, toxicity and detoxification methods are preliminarily discussed toward the end of this review. In further research on S. nux-vomica, bioactivity-guided isolation strategies should be emphasized. Its antitumor effects should be investigated further and in vivo animal experiments should be performed alongside in vitro testing. The pharmacological activity and toxicology of strychnine [Formula: see text]-oxide and brucine [Formula: see text]-oxide should be studied to explore the detoxification mechanism associated with processing more deeply.

Toxicokinetics of strychnine and brucine after the oral administration of Biqi capsule to rats by RRLC-MS/MS.

Biqi capsule is a well-known traditional Chinese medicine formula that has been widely applied for the clinical treatment of such diseases as rheumatoid arthritis, scapulohumeral periarthritis and cervical spondylopathy. However, there is concern regarding the toxicity of Biqi capsule owing to its active ingredients, strychnine and brucine. To investigate the toxicokinetics of strychnine and brucine after oral administration of Biqi capsule to rats, a sensitive and simple rapid-resolution liquid chromatography/tandem mass spectrometry method was developed to determine the levels of strychnine and brucine in rat plasma. Chromatographic separation was performed on a Capcell Pak C18 MG II (3.0 µm, 2.0 × 35 mm) column by gradient elution with acetonitrile and 0.2% formic acid as the mobile phase. The method was validated over the range of 0.25-250 ng/mL for strychnine and 0.025-25 ng/mL for brucine. The intra- and inter-day accuracies of strychnine and brucine in rat plasma were 100.3-106.6 and 90.75-106.1% respectively, and the precisions were within 14.2%. The established method was successfully applied to the toxicokinetic study of strychnine and brucine after single and multiple oral administration of Biqi capsule to male and female rats at 0.4, 0.8 and 1.6 g/kg doses. The results showed different toxicokinetic characteristics in the different groups.

Phenylalanine derivatives with modulating effects on human α1-glycine receptors and anticonvulsant activity in strychnine-induced seizure model in male adult rats.

The critical role of α1-glycine receptor (α1-GLYRs) in pathological conditions such as epilepsy is well known. In the present study, structure-activity relations for a series of phenylalanine derivatives carrying selected hydrogen bond acceptors were investigated on the functional properties of human α1-GLYR expressed in Xenopus oocytes. The results indicate that one particular substitution position appeared to be of special importance for control of ligand activity. Among tested ligands (1-8), the biphenyl derivative (2) provided the most promising antagonistic effect on α1-GLYRs, while its phenylbenzyl analogue (5) exhibited the highest potentiation effect. Moreover, ligand 5 with most promising potentiating effect showed in-vivo moderate protection when tested in strychnine (STR)-induced seizure model in male adult rats, whereas ligand 2 with highest antagonistic effect failed to provide appreciable anti(pro)convulsant effect. Furthermore, ligands 2 and 5 with the most promising effects on human α1-GLYRs were examined for their toxicity and potential neuroprotective effect against neurotoxin 6-hydroxydopamine (6-OHDA). The results show that ligands 2 and 5 possessed neither significant antiproliferative effects, nor necrotic and mitochondrial toxicity (up to concentration of 50µM). Moreover, ligand 2 showed weak neuroprotective effect at the 50µM against 100µM toxic dose of 6-OHDA. Our results indicate that modulatory effects of ligands 2 and 5 on human α1-GLYRs as well as on STR-induced convulsion can provide further insights for the design of therapeutic agents in treatment of epilepsy and other pathological conditions requiring enhanced activity of inhibitory glycine receptors.

Chronic GABAergic blockade in the spinal cord in vivo induces motor alterations and neurodegeneration.

Inhibitory GABAergic and glycinergic neurotransmission in the spinal cord play a central role in the regulation of neuronal excitability, by maintaining a balance with the glutamate-mediated excitatory transmission. Glutamatergic agonists infusion in the spinal cord induce motor neuron death by excitotoxicity, leading to motor deficits and paralysis, but little is known on the effect of the blockade of inhibitory transmission. In this work we studied the effects of GABAergic and glycinergic blockade, by means of microdialysis perfusion (acute administration) and osmotic minipumps infusion (chronic administration) of GABA and glycine receptors antagonists directly in the lumbar spinal cord. We show that acute glycinergic blockade with strychnine or GABAergic blockade with bicuculline had no significant effects on motor activity and on motor neuron survival. However, chronic bicuculline infusion, but not strychnine, induced ipsilateral gait alterations, phalange flaccidity and significant motor neuron loss, and these effects were prevented by AMPA receptor blockade with CNQX but not by NMDA receptor blockade with MK801. In addition, we demonstrate that the chronic infusion of bicuculline enhanced the excitotoxic effect of AMPA, causing faster bilateral paralysis and increasing motor neuron loss. These findings indicate a relevant role of GABAergic inhibitory circuits in the regulation of motor neuron excitability and suggest that their alterations may be involved in the neurodegeneration processes characteristic of motor neuron diseases such as amyotrophic lateral sclerosis.

A population model of the impact of a rodenticide containing strychnine on Great Basin Gophersnakes (Pituophis catenifer deserticola).

Strychnine is a neurotoxin and an active ingredient in some rodenticides which are placed in burrows to suppress pocket gopher (Thomomys talpoides) populations in range and crop land in western North America. The population level impact was modelled of the use of strychnine-based rodenticides on a non-target snake species, the Great Basin Gophersnake (Pituophis catenifer deserticola), which is a predator of pocket gopher and a Species at Risk in Canada. Using information on population density, demographics, and movement and habitat suitability for the Gophersnake living in an agricultural valley in BC, Canada, we estimated the impact of the poisoning of adult snakes on the long-term population size. To determine the area where Gophersnakes could be exposed to strychnine, we used vendor records of a rodenticide, and quantified the landcover areas of orchards and vineyards where the compound was most commonly applied. GIS analysis determined the areas of overlap between those agricultural lands and suitable habitats used by Gophersnakes. Stage-based population matrix models revealed that in a low density (0.1/ha) population scenario, a diet of one pocket gopher per year wherein 10 % of them carried enough strychnine to kill an adult snake could cause the loss of 2 females annually from the population and this would reduce the population by 35.3 % in 25 years. Under the same dietary exposure, up to 35 females could die per year in a high density (0.4/ha) population which would result in a loss of 50 % of adults in 25 years.

Theanine enhanced both the toxicity of strychnine and anticonvulsion of pentobarbital sodium.

CONTEXT: Theanine, an additive, holds several effects on the central nervous system without toxicity and affects CNS drugs. Theanine bilaterally alters ß wave of the EEG with or without caffeine and pentobarbital-induced locomotor activity. Theanine also enhances hypnosis of pentobarbital sodium (PB) and antidepression of midazolam, suggesting there are complicated interactions between theanine and CNS drugs. On the other side, theanine induces glycine release. Glycine potentiates the strychnine toxicity via NMDA receptor activation. Moreover, PB facilitates GABAA receptor activation by GABA, and it is commonly prescribed for strychnine poison. However, what the role that theanine plays in the anticonvulsion of PB against strychnine poison is still unknown. MATERIALS AND METHODS: Theanine, pentobarbital sodium or strychnine was injected intraperitoneally. EEG was monitored by BIOPAC 16 EEG amplifiers. LD50 of strychnine and hypnotic ED50 of pentobarbital sodium with or without theanine for mice were tested according to Bliss' case. RESULTS: (1) Theanine enhanced the strychnine toxicity. Both theanine and strychnine 1.0 mg/kg increased the power of the ß wave. Theanine aggravated that of strychnine 1.0 mg/kg. Theanine attenuated the LD50 of strychnine. (2) Theanine enhanced the anticonvulsion of PB. Theanine increased the power of α, ß wave and decreased hypnotic ED50 of PB; PB attenuated strychnine-induced EEG excitation and mortality with or without theanine, and theanine enhanced the effects of PB. Further, theanine enhanced the anticonvulsion of PB dose-dependently against the strychnine toxicity but not the lethal toxicity of strychnine. DISCUSSION AND CONCLUSIONS: These results indicated theanine interacted with PB and strychnine. Theanine enhanced both the strychnine toxicity and anticonvulsion of PB against strychnine poison.

A Highly Selective Inhibitor of Glycine Transporter-1 Elevates the Threshold for Maximal Electroshock-Induced Tonic Seizure in Mice.

Many anti-epileptic drugs (AEDs) that mainly target ion channels or post-synaptic receptors are in clinical use, but a proportion of patients are resistant to these traditional AEDs and experience repeated severe break-out seizures. Given its involvement in the etiology of epilepsy, the neurotransmitter glycine may serve as a novel target for epilepsy treatment. Increasing evidence suggests that inhibitors of glycine transporter 1 (GlyT1) exhibit anti-seizure properties in mouse models and show potential as anti-convulsions drugs. In the present study, we investigated the effect of a highly selective GlyT1 inhibitor (named M22) on glycine transport kinetics using a radioactive substrate uptake assay and investigated the anti-seizure effects of M22 on the maximal electroshock seizure threshold (MEST) test and the timed intravenous (i.v.) pentylenetetrazole (PTZ) intravenous test. Our results demonstrate that M22 was capable of elevating the seizure threshold in the MEST test but did not alter the seizure threshold in the PTZ i.v. test. Strychnine, an inhibitor of glycine receptor activity, reversed the threshold elevation at a subconvulsive dosage (0.1 mg/kg subcutaneously) in the MEST test and did not affect M22 plasma levels in mice, suggesting that the anti-seizure effect in this model may be mediated by increased glycine receptor activity. Moreover, M22 administration did not influence motor function and coordination in mice. In combination with the previously reported excellent pharmacokinetic features of M22, our present results suggested that M22 has the potential to serve as a new anti-convulsive drug or as a lead compound for the development of AEDs.

Zebrafish model for assessing induced organ toxicity by Strychnos nux-vomica.

OBJECTIVE: To assess the acute organ toxicity of Strychnos nux-vomica with zebrafish model visually. METHODS: To assess acute toxicity, we initially determined the lethal concentration after Strychnos nux-vomica treatment for 24 h. Zebrafish was treated with five concentrations ≦ LC10 for 24 h, and the effects of Strychnos nux-vomica on morphology, function of heart, central nervous system, liver, kidney and organ-specific cell death were assessed. Next, we assessed the reversibility of toxic effect. RESULTS: Strychnos nux-vomica has an effect on the different organs of zebrafish, including heart, central nervous system, liver, and kidney, and cadiotoxicity induced by Strychnos nux-vomica was reversible to some extent. CONCLUSION: Zebrafish model is suitable for confirming the toxic target organs for Chinese traditional medicine.

Cytotoxicity and DNA interaction of brucine and strychnine-Two alkaloids of semen strychni.

The cytotoxicities of the two alkaloids strychnine and brucine from the seed of Strychnos nux-vomica and their interaction with DNA were investigated. A 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrasolium bromide (MTT) assay was used to examine the growth inhibitory effects of these alkaloids on Vero cells after 24, 48 and 72h of incubation. The cytotoxicities of strychnine and brucine were found to be time- and concentration-dependent. Strychnine was determined to be more toxic to Vero cells than brucine. At the same time, the interactions of strychnine and brucine with DNA were investigated using neutral red (NR) dye as a probe by UV-vis spectroscopy, fluorescence spectroscopy, and an examination of the ionic strength effect, and the effects of alkaloids on DNA melting were also examined. The results indicated that a DNA-brucine mixture but not a DNA-strychnine mixture could be extracted from Vero cells after treatment with brucine and strychnine, respectively. Brucine competitively intercalated into the DNA double-helix causing fluorescence quenching of the DNA-NR system. UV absorption spectroscopy and the melting temperature (Tm) curve also provided evidence that brucine interacted with DNA through intercalation. Furthermore, the results of the ionic strength effect experiment suggested that electrostatic interactions between brucine and phosphate groups in the DNA backbone might also play an important role in the binding of brucine to DNA.