Effects Of Strychnine Research Articles

Antiproliferative and apoptotic effects of strychnine in human hepatoma HepG2 cells and its mechanism

Hepatocellular carcinoma has the highest prevalence with poor prognosis in liver cancers. Effective treatment strategies are urgently needed to improve the survival of patients with hepatocellular carcinoma. Strychnine, the major active ingredient of the seed of Strychnos nux-vomica L., has been reported to possess an anti-hepatocellular carcinoma function while the underlying mechanism is not fully understood. Here we aim to explore strychnine’s effect on the proliferation and apoptosis of human hepatoma HepG2 cells and clarify mechanism. The cytotoxic activity of strychnine against HepG2 cells was measured. Flow cytometry was used to assess cell apoptosis. The miR-122 expression level was measured via real time quantitative PCR and cyclin G1 and anti-apoptotic proteins including survivin and livin were assessed using Western blot. Strychnine decreased the viability of hepatocellular carcinoma cells and induced their apoptosis in vitro. The levels of livin and survivin were decreased in HepG2 cells after strychnine treatment. By restraining cyclin G1 expression in HepG2 cells, strychnine upregulated liver-specific miR-122 level for the induction of apoptosis. Therefore, strychnine possessed the ability to inhibit cell proliferation and induce apoptosis. Strychnine may be applied for treating liver cancer.

Anti-Strychnine Immunoconjugate Reduces the Effects of Strychnine-Induced Toxicity in Mice.

Strychnine poisoning induces seizures that result in loss of control of airway muscles, leading to asphyxiation and subsequent death. Current treatment options are limited, requiring hands-on medical care and isolation to low-stimulus environments. Anticonvulsants and muscle relaxants have shown limited success in cases of severe toxicity. Furthermore, nonfatal strychnine poisoning is likely to result in long-term muscular and cognitive damage. Due to its potency, accessibility, and lack of effective antidotes, strychnine poses a unique threat for mass casualty incidents. As a first step toward developing an anti-strychnine immunotherapy to reduce or prevent strychnine-induced seizures, a strychnine vaccine was synthesized using subunit keyhole limpet hemocyanin. Mice were vaccinated with the strychnine immunoconjugate and then given a 0.75 mg/kg IP challenge of strychnine and observed for seizures for 30 min. Vaccination reduced strychnine-induced events, and serum strychnine levels were increased while brain strychnine levels were decreased in vaccinated animals compared to the control. These data demonstrate that strychnine-specific antibodies can block the seizure-inducing effects of strychnine and could be used to develop a therapeutic for strychnine poisoning.

Effect of a combination of Atractylodes macrocephala extract with strychnine on the TLR4/NF-κB/NLRP3 pathway in MH7A cells.

Rheumatoid arthritis (RA) is now widely recognized as a chronic systemic inflammatory autoimmune disease characterized by swelling, pain and stiffness, which are often disabling. Although the number of drugs available for the treatment of RA has increased in recent years, they are generally expensive, leave patients prone to relapse and can result in severe effects when discontinued. Thus, there is a need for an inexpensive drug with fewer side effects that can be adhered to relieve pain and slow down the progression of the disease. Strychnine, a traditional Chinese medicine, was often used in ancient times to treat swollen and painful joints; however, because of its somewhat toxic nature, it is often combined with Atractylodes macrocephala to reduce its toxicity for safer therapeutic action. The present study performed high-performance liquid chromatography (HPLC)-tandem mass spectrometry (MS/MS) analysis to confirm whether the use of strychnine with Atractylodes macrocephala had the effect of reducing strychnine content. MH7A cells were induced using IL-1β to study the effect of strychnine with Atractylodes macrocephala on the Toll-like receptor 4 (TLR4)/NF-κB/NLR family pyrin domain-containing 3 (NLRP3) pathway in order to verify its role in the treatment of RA. The results indicated that the combined application of HPLC-MS/MS strychnine and Atractylodes macrocephala had a reducing effect on the strychnine content. From the subsequent experimental results, it can be inferred that Strychnine combined with Atractylodes macrocephala extract could promote the apoptosis of synovial cells, and could inhibit the expression levels of TLR4, NF-κB and NLRP3 in the cells as well as reducing the MH7A-positive cells. The expression levels of TLR4, IκB kinase β, NF-κB and NLRP3 were significantly reduced after treatment with each administration group, resulting in a decrease in the phosphorylation levels of TLR4 and NF-κB, indicating that the combination potently inhibited their phosphorylation. The combination of strychnine and atractylenolide II was also revealed to be the main active ingredient in the treatment of RA.

CYP3A1 metabolism-based neurotoxicity of strychnine in rat

Strychnine is one of the main bioactive and toxic constituents of Semen Strychni. In the present study, the neurotoxic effects of strychnine, and the role of individual differences in metabolism on susceptibility to neurotoxicity of strychnine were investigated. The acute toxicity was observed by a single dose of strychnine (2.92 mg/kg, i.g.) in rats, the epileptic stages of rats were scored according to Racine’s scale. The neurotoxicity of strychnine was evaluated by the levels of ROS, MDA, SOD and GSH in hippocampus, striatum, and cortex tissues measurements and histopathological analysis. The concentrations of strychnine in the plasma, hippocampus, striatum, and cortex tissues were determined using high performance liquid chromatography tandem mass spectrometry (LC-MS/MS). The expressions of the cytochrome P450, which is the most critical protein family involved in drugs metabolism, were detected by proteomics. The mechanism of susceptibility to neurotoxicity of strychnine was elucidated by correlation analysis among above indicators. The results indicated that striatum and cortex were the main toxic targets of strychnine, and the CYP3A1 might be a susceptible biomarker to neurotoxicity of strychnine. These results provide valuable insights into the neurotoxic susceptibility of strychnine that will aid in the rational clinical use of strychnine (possibly including Semen Strychni).

Effect of Brucine on Three Chondrocyte Apoptosis Models

With the development of people’s application technology of Strychnine, Strychnine is a relatively common type of medicine in the current clinical treatment of arthritis patients. And in the actual treatment, because strychnine has an important effect on the apoptosis of three kinds of chondrocytes. Better results can often be achieved through the use of horse money, which is of great significance to patients. The analysis of the influence of strychnose on the apoptosis of the three types of chondrocytes has become the focus of research in the academic and industry circles. The purpose of this article is to analyze the impact of Strychnoma chinensis on three chondrocyte apoptosis models. In this paper, by establishing a system for culturing rat chondrocytes in vitro, using nitric oxide in vitro cultured rat chondrocytes to induce their apoptosis, and observing the effect of Strychnine, the main monomer component of Chinese medicine Strychnine, on the cellular and molecular levels. The mechanism of SD rat chondrocyte apoptosis is to explore the establishment of a system for culturing rat chondrocytes in vitro. In this paper, rat chondrocytes cultured in vitro were induced by nitric oxide to induce their apoptosis, and the mechanism of strychnine, the main monomer component of Strychnine, was observed in order to explore the mechanism of strychnine on the apoptosis of SD rat chondrocytes in vitro. The experimental results showed that strychnine induced apoptosis of chondrocytes, and the survival rate of cells during 36h and 48h after administration was 99% and 97%, respectively. Its apoptotic rate decreases with the increase of the dose and time of strychnine.

Blocking glycine receptors reduces neuroinflammation and restores neurotransmission in cerebellum through ADAM17-TNFR1-NF-\u03ba\u03b2 pathway

BackgroundChronic hyperammonemia induces neuroinflammation in cerebellum, with glial activation and enhanced activation of the TNFR1-NF-kB-glutaminase-glutamate-GABA pathway. Hyperammonemia also increases glycinergic neurotransmission. These alterations contribute to cognitive and motor impairment. Activation of glycine receptors is reduced by extracellular cGMP, which levels are reduced in cerebellum of hyperammonemic rats in vivo.We hypothesized that enhanced glycinergic neurotransmission in hyperammonemic rats (1) contributes to induce neuroinflammation and glutamatergic and GABAergic neurotransmission alterations; (2) is a consequence of the reduced extracellular cGMP levels. The aims were to assess, in cerebellum of hyperammonemic rats, (a) whether blocking glycine receptors with the antagonist strychnine reduces neuroinflammation; (b) the cellular localization of glycine receptor; (c) the effects of blocking glycine receptors on the TNFR1-NF-kB-glutaminase-glutamate-GABA pathway and microglia activation; (d) whether adding extracellular cGMP reproduces the effects of strychnine.MethodsWe analyzed in freshly isolated cerebellar slices from control or hyperammonemic rats the effects of strychnine on activation of microglia and astrocytes, the content of TNFa and IL1b, the surface expression of ADAM17, TNFR1 and transporters, the phosphorylation levels of ERK, p38 and ADAM17. The cellular localization of glycine receptor was assessed by immunofluorescence. We analyzed the content of TNFa, IL1b, HMGB1, glutaminase, and the level of TNF-a mRNA and NF-κB in Purkinje neurons. Extracellular concentrations of glutamate and GABA were performed by in vivo microdialysis in cerebellum. We tested whether extracellular cGMP reproduces the effects of strychnine in ex vivo cerebellar slices.ResultsGlycine receptors are expressed mainly in Purkinje cells. In hyperammonemic rats, enhanced glycinergic neurotransmission leads to reduced membrane expression of ADAM17, resulting in increased surface expression and activation of TNFR1 and of the associated NF-kB pathway. This increases the expression in Purkinje neurons of TNFa, IL-1b, HMGB1, and glutaminase. Increased glutaminase activity leads to increased extracellular glutamate, which increases extracellular GABA. Increased extracellular glutamate and HMGB1 potentiate microglial activation. Blocking glycine receptors with strychnine or extracellular cGMP completely prevents the above pathway in hyperammonemic rats.ConclusionsGlycinergic neurotransmission modulates neuroinflammation. Enhanced glycinergic neurotransmission in hyperammonemia would be due to reduced extracellular cGMP. These results shed some light on possible new therapeutic target pathways for pathologies associated to neuroinflammation.

Sarcophine and (7S, 8R)-dihydroxydeepoxysarcophine from the Red Sea soft coral Sarcophyton glaucum as in vitro and in vivo modulators of glycine receptors

The inhibitory glycine receptor (GlyR) is a key mediator of synaptic signalling in spinal cord, brain stem, and higher centres of the central nervous system. We examined the glycinergic activity of sarcophine (SN), a marine terpenoid known for its various biological activities, and its trans-diol derivative (7S, 8R)-dihydroxy-deepoxysarcophine (DSN). SN was isolated from the Red Sea soft coral Sacrophyton glaucum, DSN was semisynthesized by hydrolysis of the epoxide ring. In cytotoxicity tests against HEK293 cells, SN and DSN had LD50 values of 29.3 ± 3.0 mM and 123.5 ± 13.0 mM, respectively. Both compounds were tested against recombinant human α1 glycine receptors in HEK293 cells using whole-cell recording techniques. Both, SN and DSN were shown for the first time to be inhibitors of recombinant glycine receptors, with KIvalues of 2.1 ± 0.3 μM for SN, and 109 ± 9 μM for DSN. Receptor inhibition was also studied in vivo in a mouse model of strychnine toxicity. Surprisingly, in mouse experiments strychnine inhibition was not augmented by either terpenoid. While DSN had no significant effect on strychnine toxicity, SN even delayed strychnine effects. This could be accounted for by assuming that strychnine and sarcophine derivatives compete for the same binding site on the receptor, so the less toxic sarcophine can prevent strychnine from binding. The combination of modulatory activity and low level of toxicity makes sarcophines attractive structures for novel glycinergic drugs.

0066 Glycinergic Postsynaptic Inhibition is Responsible for the Suppression of Hypoglossal Motoneuron Activity During Naturally-Occurring REM Sleep

Abstract Introduction The present study was undertaken to explore the role of glycinergic postsynaptic inhibition and monoaminergic disfacilitation (a withdrawal of excitatory noradrenergic and serotonergic inputs) in the control of hypoglossal motoneuron activity during REM sleep. Accordingly, glycinergic, noradrenergic and serotonergic antagonists were microinjected into the hypoglossal nucleus, and their effects on the hypoglossal nerve activity during REM sleep were examined in chronically-instrumented, unanesthetized cats. Methods Adults cats were prepared for monitoring behavioral states of sleep and wakefulness, and for extracellular recordings from hypoglossal nerve. Strychnine (a glycinergic antagonist) and a mixture of prazosin (a noradrenergic antagonist) and methysergide (a serotonergic antagonist) were microinjected, separately, into the hypoglossal nucleus during naturally-occurring states of sleep and wakefulness. Results During REM sleep, compared to non-REM sleep, the hypoglossal nerve activity decreased by 17.4±1.5% (n=17) in the control recordings (prior to the injection of strychnine). Following the microinjection of strychnine, there was only a mean decrease of 7.2±1.2% (n=12) in the nerve activity during REM sleep versus NREM sleep. The strychnine effect was statistically significant compared to control (p<0.001; unpaired t-test), which indicates that strychnine blocks REM sleep-related suppression of hypoglossal nerve activity. In contrast, the microinjection of prazosin and methysergide did not significantly reduce the hypoglossal nerve activity during REM sleep (control: 15.9±2.3, n=9 vs. prazosin+methysergide: 12.6±1.4%, n=10, p=0.229, unpaired t-test). Conclusion The present results demonstrate that the microapplication of strychnine, but not prazosin and methysergide, into the hypoglossal nucleus significantly reduces the suppression of the hypoglossal nerve activity during naturally-occurring REM sleep. We therefore suggest that glycinergic postsynaptic inhibition is primarily responsible for the suppression of hypoglossal motoneuron activity during REM sleep. Support 5R01NS094062

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 of M in comparison to that of Dofetilide at M and Quinidine at M. Langendorff-perfusion experiments confirmed that strychnine increased QT interphase from ms to ms and decreased heart rates from bmp to 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.

Nonsynaptic glycine release is involved in the early KCC2 expression.

The cation-chloride co-transporters are important regulators of the cellular Cl(-) homeostasis. Among them the Na(+) -K(+) -2Cl(-) co-transporter (NKCC1) is responsible for intracellular chloride accumulation in most immature brain structures, whereas the K(+) -Cl(-) co-transporter (KCC2) extrudes chloride from mature neurons, ensuring chloride-mediated inhibitory effects of GABA/glycine. We have shown that both KCC2 and NKCC1 are expressed at early embryonic stages (E11.5) in the ventral spinal cord (SC). The mechanisms by which KCC2 is prematurely expressed are unknown. In this study, we found that chronically blocking glycine receptors (GlyR) by strychnine led to a loss of KCC2 expression, without affecting NKCC1 level. This effect was not dependent on the firing of Na(+) action potentials but was mimicked by a Ca(2+) -dependent PKC blocker. Blocking the vesicular release of neurotransmitters did not impinge on strychnine effect whereas blocking volume-sensitive outwardly rectifying (VSOR) chloride channels reproduced the GlyR blockade, suggesting that KCC2 is controlled by a glycine release from progenitor radial cells in immature ventral spinal networks. Finally, we showed that the strychnine treatment prevented the maturation of rhythmic spontaneous activity. Thereby, the GlyR-activation is a necessary developmental process for the expression of functional spinal motor networks. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 764-779, 2016.

Cyclodextrin Alters GABAergic Input to CA1 Pyramidal Cells in Wild-Type But Not in NPC1-Deficient Mice.

Niemann–Pick type C1 disease (NPC1) is a neurodegenerative disorder caused by mutations in the NPC1 gene. Actual, no causative treatment for NPC1 is available, although some drugs have been proven to be beneficial to patients, for example, 2-hydroxypropyl-β-cyclodextrin (CDX). In this study, we used the BALB/c_Nctr-Npc1m1N/-J mouse strain to study the effect of CDX, which is described to prolong the life span and to alleviate the pathogenic phenotype. By means of patch clamp recordings, we measured inhibitory postsynaptic currents (IPSCs) of CA1 pyramidal cells of CDX-treated and -untreated animals to elucidate the influence of CDX on the synaptic transmission. Surprisingly, CDX induced a significantly higher GABAergic IPSC frequency in wild-type mice than in NPC1−/− mice. Although the IPSCs were mainly GABAergic, we observed a significant reduction of the IPSC frequency in the presence of the glycine receptor antagonist strychnine. The effect of strychnine did not differ in untreated and treated animals, indicating that the effect of CDX was most likely not based on an interaction with glycinergic transmission machinery. However, the unexpected effect of CDX on the GABAergic synaptic transmission is of special interest as a disturbance plays, for example, a crucial role in epilepsy and, moreover, as CDX is currently under investigation as a treatment for NPC1 in humans.

Toxic effects of strychnine and strychnine N-oxide on zebrafish embryos

AimThe application of strychnine (S) is limited due to its toxicity; strychnine N-oxide (SNO) is a derivative of strychnine. The aim was to employ zebrafish embryos to investigate and compare the developmental toxicity induced by S and SNO. MethodsThe toxicity of S and SNO was examined through the hatching rate and survival rate. Morphological changes of the zebrafish were observed with a dissecting microscope. Apoptosis was detected through acridine orange (AO) staining and flow cytometry. Apoptotic genes were measured by RT-PCR. ResultsEmbryo malformation was observed in the embryos exposed to S at 200 μmol·L−1. When SNO concentration was increased to 1 mmol·L−1, scoliolosis, and pericardial edema could be seen in some embryos. Results from fluorescence microscopy and flow cytometry analysis showed that S at 200 μmol·L−1 induced apoptosis, whereas the apoptotic rate in the SNO-treated group (200 μmol·L−1) was much lower than that in the S group. RT-PCR analysis showed that p53 mRNA expression and the ratio of Bax/Bcl-2 in the S group were significantly altered compared with the control group (*P < 0.05). Moreover, Bax mRNA expression in both S and SNO group were significantly different from that in the control group (**P <0.01). ConclusionThese results lead to the conclusion that SNO has significantly lower toxicity than S in zebrafish embryos.

In vivo protection against strychnine toxicity in mice by the glycine receptor agonist ivermectin.

The inhibitory glycine receptor, a ligand-gated ion channel that mediates fast synaptic inhibition in mammalian spinal cord and brainstem, is potently and selectively inhibited by the alkaloid strychnine. The anthelminthic and anticonvulsant ivermectin is a strychnine-independent agonist of spinal glycine receptors. Here we show that ivermectin is an effective antidote of strychnine toxicity in vivo and determine time course and extent of ivermectin protection. Mice received doses of 1 mg/kg and 5 mg/kg ivermectin orally or intraperitoneally, followed by an intraperitoneal strychnine challenge (2 mg/kg). Ivermectin, through both routes of application, protected mice against strychnine toxicity. Maximum protection was observed 14 hours after ivermectin administration. Combining intraperitoneal and oral dosage of ivermectin further improved protection, resulting in survival rates of up to 80% of animals and a significant delay of strychnine effects in up to 100% of tested animals. Strychnine action developed within minutes, much faster than ivermectin, which acted on a time scale of hours. The data agree with a two-compartment distribution of ivermectin, with fat deposits acting as storage compartment. The data demonstrate that toxic effects of strychnine in mice can be prevented if a basal level of glycinergic signalling is maintained through receptor activation by ivermectin.

Strychnine inhibits inflammatory angiogenesis in mice via down regulation of VEGF, TNF-α and TGF-β

Strychnine is known to possess anti-inflammatory and antitumour activity, but its roles in tumour angiogenesis, the key step involved in tumour growth and metastasis, and the involved molecular mechanism are still unknown. We aimed to investigate the effects of strychnine on key components of inflammatory angiogenesis in the murine cannulated sponge implant angiogenesis model. Polyester–polyurethane sponges, used as a framework for fibrovascular tissue growth, were implanted in Swiss albino mice and strychnine (0.25, and 0.5mg/kg/day) was given through installed cannulas for 9days. The implants collected at day 9 postimplantation were processed for the assessment of haemoglobin (Hb), myeloperoxidase (MPO), N-acetylglucosaminidase (NAG) and collagen used as indexes for angiogenesis, neutrophil and macrophage accumulation and extracellular matrix deposition, respectively. Relevant inflammatory, angiogenic and fibrogenic cytokines were also determined. Strychnine treatment attenuated the main components of the fibrovascular tissue, wet weight, vascularization (Hb content), macrophage recruitment (NAG activity), collagen deposition and the levels of vascular endothelial growth factor (VEGF), tumour Necrosis Factor (TNF)-α and transforming growth factor (TGF-β). A regulatory function of strychnine on multiple parameters of main components of inflammatory angiogenesis has been revealed giving insight into the potential therapeutic underlying the actions of strychnine.

Effect of strychnine on the rat electroretinogram.

Journal Article Effect of strychnine on the rat electroretinogram Get access S F Pong, S F Pong Section of Neurobiology, Institute of Psychiatric Research, Indiana University Medical Center, Indianapolis, Indiana 46202, USA Search for other works by this author on: Oxford Academic Google Scholar L T Graham L T Graham Section of Neurobiology, Institute of Psychiatric Research, Indiana University Medical Center, Indianapolis, Indiana 46202, USA Correspondence: Department Of Biochemistry and Molecular Biology, LSU School Of Medicine, Shreveport, Louisiana 71130, U.S.A. Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 30, Issue 1, September 1978, Pages 327–328, https://doi.org/10.1111/j.2042-7158.1978.tb13245.x Published: 12 April 2011 Article history Received: 09 January 1978 Published: 12 April 2011

Cardiac effects of strychnine and their mechanism.

Cardiac effects of strychnine and their mechanism.

Direct and indirect control of orexin/hypocretin neurons by glycine receptors.

Hypothalamic hypocretin/orexin (hcrt/orx) neurons promote arousal and reward seeking, while reduction in their activity has been linked to narcolepsy, obesity and depression. However, the mechanisms influencing the activity of hcrt/orx networks in situ are not fully understood. Here we show that glycine, a neurotransmitter best known for its actions in the brainstem and spinal cord, elicits dose dependent postsynaptic Cl⁻ currents in hcrt/orx cells in acute mouse brain slices. The effect was blocked by the glycine receptor (GLyR) antagonist strychnine and mimicked by the GlyR agonist alanine. Postsynaptic GlyRs on hcrt/orx cells remained functional during both early postnatal and adult periods, and gramicidin-perforated patch-clamp recordings revealed that they progressively switch from excitatory to inhibitory during the first two postnatal weeks. The pharmacological profile of the glycine response suggested that developed hcrt/orx neurons contain α/β-heteromeric GlyRs that lack α2-subunits, whereas α2-subunits, whereas α2-subunits are present in early postnatal hcrt/orx neurons. All postsynaptic currents (PSCs) in developed hcrt/orx cells were blocked by inhibitors of GABA and glutamate receptors, with no evidence of GlyR-mediated PSCs. However, the frequency but not amplitude of miniature PSCs was reduced by strychnine and increased by glycine in ~50% of hcrt/orx neurons. Together, these results provide the first evidence for functional GlyRs in identified hcrt/orx circuits and suggest that the activity of developed hcrt/orx cells is regulated by two GlyR pools: inhibitory extrasynaptic GlyRs located on all hcrt/orx cells and excitatory GlyRs located on presynaptic terminals contacting some hcrt/orx cells.

Pharmacology of Intracisternal or Intrathecal Glycine, Muscimol, and Baclofen in Strychnine-induced Thermal Hyperalgesia of Mice

Glycine and γ-aminobutyric acid (GABA) are localized and released by the same interneurons in the spinal cord. Although the effects of glycine and GABA on analgesia are well known, little is known about the effect of GABA in strychnine-induced hyperalgesia. To investigate the effect of GABA and the role of the glycine receptor in thermal hyperalgesia, we designed an experiment involving the injection of muscimol (a GABAA receptor agonist), baclofen (a GABAB receptor agonist) or glycine with strychnine (strychnine sensitive glycine receptor antagonist). Glycine, muscimol, or baclofen with strychnine was injected into the cisterna magna or lumbar subarachnoidal spaces of mice. The effects of treatment on strychnine-induced heat hyperalgesia were observed using the pain threshold index via the hot plate test. The dosages of experimental drugs and strychnine we chose had no effects on motor behavior in conscious mice. Intracisternal or intrathecal administration of strychnine produced thermal hyperalgesia in mice. Glycine antagonize the effects of strychnine, whereas, muscimol or baclofen does not. Our results indicate that glycine has anti-thermal hyperalgesic properties in vivo; and GABA receptor agonists may lack the binding abilities of glycine receptor antagonists with their sites in the central nervous system.

Behavior and Cellular Evidence for Propofol-induced Hypnosis Involving Brain Glycine Receptors

It is well documented that several general anesthetics, including propofol, potentiate glycine receptor function. Furthermore, glycine receptors exist throughout the central nervous system, including areas of the brain thought to be involved in sleep. However, the role of glycine receptors in anesthetic-induced hypnosis has not been determined. Experiments were conducted in rats where the loss of righting reflex (LORR) was used as a marker of the hypnotic state. Propofol-induced LORR was examined in the presence and absence of strychnine (a glycine receptor antagonist), GABAzine (a gamma-aminobutyric acid A receptor antagonist), as well as ketamine (an antagonist of N-methyl-D-aspartic acid subtype of glutamate receptors). Furthermore, the effects of propofol on the currents elicited by glycine and gamma-aminobutyric acid were analyzed in neurons isolated from the posterior hypothalamus of rats. The effects of strychnine and GABAzine on propofol-induced currents were also evaluated. Strychnine and GABAzine dose-dependently reduced the percentage of rats exhibiting LORR induced by propofol. Furthermore, strychnine significantly increased the onset time and reduced the duration of LORR induced by propofol. In contrast, strychnine did not affect the LORR induced by ketamine. In addition, propofol markedly increased the currents elicited by glycine and GABA of hypothalamic neurons. Conversely, strychnine and GABAzine both profoundly attenuated the current induced by propofol. Strychnine, the glycine receptor antagonist, dose-dependently reduced propofol-induced LORR in rats and propofol-induced current of rat hypothalamic neurons. These results suggest that neuronal glycine receptors partially contribute to propofol-induced hypnosis.

Oral administration of diphenyl diselenide potentiates hepatotoxicity induced by carbon tetrachloride in rats

Carbon tetrachloride (CCl4) is a model for studying free radical-induced liver injury and screening hepato-protective drugs. Numerous studies have reported the involvement of oxidative stress in CCl4-induced liver damage and the hepato-protective effects mediated by different antioxidants. The present study examined the effects of diphenyl diselenide, (PhSe)2, on hepatotoxicity induced by CCl4 in rats. To this end, male Wistar rats received (PhSe)2 by oral route at the dosage of 31.2 mg/kg for one or two days. After the second day of treatment, rats received CCl4 orally in a single dose. The liver and kidney were utilized for determination of histopathology, biochemical [aspartate (ALT) and alanine (AST) aminotransferases, alkaline phosphatase (ALP), total bilirrubin (TB) and gamaglutamyl transferase (GGT)] and toxicological parameters [thiobarbituric reactive species (TBARS) levels, catalase activity, ascorbic acid, nonprotein thiols (NPSH) and aminolevulinate dehydratase (-ALA-D) activity]. Repeated administration of (PhSe)2 caused a marked potentiation of hepatotoxicity induced by CCl4 exposure, as manifested by an increase in biochemical parameters (AST, ALT, ALP, GGT and BT) and severe alteration in histopathology. This study also demonstrated a potentiation of TBARS levels and a consequent depletion of important antioxidant defenses including catalase and ascorbic acid. Pre-treatment with a single dose of (PhSe)2 prevented the effect of strychnine, a substrate for CYPs, abolishing lethality in mice. This result indicates that (PhSe)2 prevented animal death, suggesting an activator action of (PhSe)2 in CYPs. This study clearly indicates that (PhSe)2 potentiated acute hepatic damage induced by CCl4.