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The potential of Strained-Promoted Sydnone-Alkyne Cycloaddition (SPSAC) for radioiodination was evaluated with model cyclooctyne-conjugated peptides. Starting with a series of sydnones with varying N 3 and C 4 substitution, a preliminary kinetic study with non-radioactive iodinated compounds highlighted the superiority of an arylsydnone substituted by a chlorine atom in C 4 position. Interestingly, reaction rate up to 11 times higher than using an azide was achieved with the best system. Access to 125 I-labelled sydnones was granted with high efficiency from arylboronic acid precursors by copper catalyzed nucleophilic substitution. Application of SPSAC on the model peptide in radiotracer conditions showed the same trend than in non-radioactive kinetic study and complete reactions could be achieved within less than an hour for the best systems. These results are favorable for use in the production of radiopharmaceuticals with heavy halogens and increase the diversity of available bioorthogonal reaction for nuclear imaging and therapy., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Mitochondria are considered to be a promising target in cancer diagnosis and therapeutics. Recently, sydnone and sydnonimine, as mesoionic bioorthogonal reagents, have been used in cell labeling and drug delivery. Here we investigated the mitochondrial targeting ability of sydnones and sydnonimines for the first time. Experimental results show that sydnone and sydnonimine themselves have high mitochondrial distribution. However, the introduction of a phenyl group into the C 4 position of sydnone dramatically decreases the mitochondrial affinity. In addition, we took advantage of mitochondrial targeting ability and click-and-release reaction of sydnonimine to evaluate anticancer activities of in-mitochondria delivery of celecoxib against HeLa and HepG2 cells, indicating that celecoxib-induced cancer cell death may not involve mitochondria-related pathway., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Objective: To evaluate the antiproliferative and apoptosis inducing activity of different sydnones on cancer cell lines and their interaction with cancer proteins by molecular docking studies., Material and Methods: Antiproliferative activity was carried out by MTT assay and apoptosis inducing activity was performed by DAPI and Annexin V and propidium iodide staining. Molecular docking studies were performed using AutoDock Tools 1.5.6. Pharmacokinetics properties like ADME and toxicity were analysed by pkCSM web server., Result: In this study, four new sydnone compounds 3-(4-nonylbiphenyl-4'-yl) sydnone (MC-182), 3-(4-propylbiphenyl-4'-yl) sydnone (MC-454), 3-(4-hexylbiphenyl-4'-yl) sydnone (MC-433), and 3-(4-methylbiphenyl-4'-yl) sydnone (MC-431) were screened for antiproliferative and apoptotic effect against BT-474 (human breast cancer), HeLa (human cervical cancer) and Jurkat (human myeloid leukemia) Mostly, all the sydnone compounds exhibited decent antiproliferative effectiveness, but compound MC-431, MC-433, and MC-454 showed more antiproliferative activity (IC50 1.71, 10.09 and 2.87 μM against BT-474, Hela and Jurkat cell line, respectively). The changes of morphological characteristics of cancer cells determined by staining techniques indicate the apoptotic cell death. The molecular docking and interaction studies were carried out between sydnones with cancer proteins (epidermal growth factor domain receptor tyrosine kinase [EGF-TK], tumor necrosis factor-alpha [TNF-α] and Caspase3. Among all four sydnone molecules, two compounds MC-454 and MC-431 showed good binding energy with targeted proteins. Drug-like property was predicted by ADME toxicity study., Conclusion: The results indicate sydnone compounds were found to exhibit anticancer activity by inducing apoptosis. The molecular docking study of sydnones with cancer proteins showed a decent interaction affinity. The results of absorption, distribution, metabolism, excretion and toxicity studies by the Insilco approach also proved that MC-454 sydnone showed better In-Vivo administration. Thus, the current research work indicates that these sydnone compounds would be prospective in developing anticancer medicines., Competing Interests: None

Triflumezopyrim (TFM) is a new mesoionic insecticide developed by DuPont. Like other neonicotinoid insecticides, it binds to the orthosteric site of the nicotinic acetylcholine receptor (nAChR), but the binding mode has not been reported. Nicotinic acetylcholine binding proteins (nAChBPs) are ideal alternative structure for nAChRs. In this study, molecular docking, molecular dynamics (MD) simulations, binding free energy calculation, and per-residue binding free energy decomposition were used to study the binding modes of TFM and other 12 mesoionic insecticides. By comparing the binding free energy and the insecticidal activity, it was found that the sub-pocket around the benzyl group of the mesoionic insecticide is the key area for maintaining its activity, which is composed of A: Val116, A: Met124, A: Ile126, B: Trp155 and B: Val156. In order to verify the druggability of the sub-pocket, a series of iminosydnone compounds were designed and synthesized based on the structure of the sub-pocket. The lethality rate of compound 1 against Mythimna separata were 100% at 500 mg/L. Our research provides a basis for designing new mesoionic insecticides based on structure., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Crop pathogens reduce the yield and quality of agricultural production. The development of new fungicides will help to sustain this protection and overcome fungicide resistance. Sydnone is a kind of mesoionic, which has a wide range of biological activities. The application of sydnones in agriculture is less, and the study of these compounds will lead to the discovery of new active compounds. In this study, we designed and synthesized a series of noval sydnone mesoionic derivatives by active substructure splicing. All compounds were characterized using 1 H and 13 C NMR spectroscopy. Among them, trifluoromethyl compound D17 showed good bioactivity against Pseudoperonospora cubensis (EC 50  = 49 mg L -1 ) in vivo, the activity was similar to that of the control Kresoxim-methyl (EC 50  = 44 mg L -1 ). However, the target of these compounds should not only be tyrosinase, and the mode of action needs to be further studied. In addition, the structure-activity relationship indicated that the trifluoromethyl group was more beneficial for antifungal activity. This is the first report that fluorine-containing N(3)-benzyl sydnone compounds have good fungicidal activity. These results will provide a basis for the development of sydnone mesoionic as new lead fungicidal agents., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

The combretastatins have attracted significant interest as small-molecule therapies for cancer due to their ability to function as vascular disrupting agents. We have successfully prepared a range of combretastatin analogues that are based on a novel sydnone heterocycle core, and their potential as tubulin binders has been assessed in vitro and in vivo. The most potent candidate was found to disrupt microtubules and affect cellular morphology at sub-micromolar levels. Moreover, it was found to bind reversibly to tubulin and significantly increase endothelial cell monolayer permeability, in a similar manner to combretastatin A4. Surprisingly, the compound did not exhibit efficacy in vivo, possibly due to rapid metabolism., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This study evaluated the antitumour activity of the mesoionic compound sydnone 1 (Syd-1) against Walker-256 carcinosarcoma. Tumour cells were subcutaneously inoculated in the hind limb in male Wistar rats. The animals were orally treated for 12 days with Syd-1 (75 mg/kg) or vehicle. At the end of treatment, considerable decreases in tumour volume and tumour weight were observed in treated animals. Samples of these tumours presented increases in apoptotic bodies and pro-apoptotic protein expression (Bax and p53), while the expression of the anti-apoptotic protein Bcl-2 was reduced. A decrease in reduced glutathione levels and an increase in glutathione peroxidase activity were observed in tumour after Syd-1 treatment. However, significant splenomegaly was evident in animals that received Syd-1, most likely attributable to the induction of haemolysis. This study demonstrated the antitumour activity of Syd-1 against Walker-256 carcinosarcoma. Its mechanism of action is linked to the activation of apoptotic pathways that lead to tumour cell death., (© 2015 Nordic Association for the Publication of BCPT (former Nordic Pharmacological Society).)

Synthesis and bioactivity of novel dual acting nitric oxide releasing and reactive oxygen scavenging hybrid compound SA-2 is described. The hybrid molecule SA-2 significantly increased the superoxide dismutase enzyme level and protected the photoreceptor cells from H2O2 induced oxidative stress. Synthesis of ocular esterase sensitive aceloxy alkyl carbamate prodrug SA-4 with improved aqueous half-life is achieved to aid topical ocular formulation. This class of hybrid molecule and prodrug may have dual potential of improved IOP lowering and neuroprotection in glaucomatous optic neuropathy., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

In a placebo-controlled study, changes in psychophysiological status of operators (38 healthy male volunteers aged 23-35 years) performing 4-hour model operator activity were evaluated after a single oral administration of typical representatives of the different classes of drugs (haloperidol, proroxan, yohimbine hydrochloride, propranolol, mesocarb, isoprenaline, Belladonna extract, anabasine hydrochloride, valproate sodium, and phenazepam), which are used for the treatment, rehabilitation and prophylaxis of common diseases. It was found that all the drugs modified to a greater or lesser extent some components of the model operator activity. Isoprenaline and phenazepam had the most negative effect on the psychophysiological indicators and quality of the modeled operator activity. The results should be considered before administration of such drugs to working operators.

Sydnones are mesoionic heterocyclic aromatic compounds. They have been widely studied for some important biological activities like antiviral, antitumor, antimicrobial, anti-inflammatory, anticancer, analgesic, anthelmintic and antihypertensive activities. The aim of the present article is to review the available information on sydnones and the derivatives of sydnones and also a look at the future perspectives.

A novel series of 1-substituted aminomethyl-3-[1-(4-isobutylphenyl)ethyl]-4-(3-aryl-4-sydnonylidene) amino-1,2,4-triazol-5-thiones (9), was prepared from the 3-[1-(4-isobutylphenyl)ethyl]-4-(3-aryl-4-sydnonylidene) amino 5-mercapto-1,2,4-triazoles (8) by aminomethylation with formaldehyde and secondary amine. The structures of Schiff bases (8) and Mannich bases (9) were characterized on the basis of IR, NMR, mass spectra1 data and elemental analysis. The newly synthesized compounds were screened for their anti-inflammatory and analgesic activities. Mannich bases (9) carrying piperidine and morpholine residues showed promising anti-inflammatory and analgesic activity., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

In continuation of structure activity relationship studies, a panel of fluorine containing sydnones with styryl ketone group 4-[1-oxo-3-(substituted aryl)-2-propenyl]-3-(3-chloro-4-fluorophenyl)sydnones 2a-i, was synthesized as better analgesic and anti-inflammatory agents. The title compounds were formed by condensing 4-acetyl-3-(3-chloro-4-fluorophenyl)sydnone with various substituted aryl aldehydes, characterized by spectral studies and evaluated at 100 mg\kg b.w., p.o. for analgesic, anti-inflammatory and ulcerogenic activities. Compounds 2c and 2e showed good analgesic effect in acetic acid-induced writhing while none showed significant activity in hot plate assay in mice. In carrageenan-induced rat paw oedema test, compound 2c and 2f exhibited good anti-inflammatory effect at 3rd h, whereas compounds 2c, 2e, 2d, 2g and 2h showed activity in croton oil induced ear oedema assay in mice. Compounds 2c and 2e were less ulcerogenic than ibuprofen in rats, when tested by ulcer index method. Compounds with electron attracting substituents such as 2c and 2e were found to be promising in terms of the ratio of efficacy and adverse effect. These compounds generally exhibited better activity than those of earlier series signifying fluorine substitution.

Sydnocarb is a psychomotor stimulant structurally similar to d-amphetamine (D-AMPH) and is used in Russia for the treatment of a variety of neuropsychiatric comorbidities. The nature of sydnocarb-induced facilitation of dopamine (DA) neurotransmission [DA release versus DA transporter (DAT) inhibition] is not clear. The present study characterized the pharmacological actions and behavioral effects of intraperitoneal sydnocarb in male Sprague-Dawley rats. Where relevant, comparisons were made with intraperitoneal D-AMPH. Unlike D-AMPH, which causes release of DA from rat synaptosomes (EC(50) = 0.10 μM; 95% confidence limits, 0.06-0.18), sydnocarb (up to 100 μM) did not. Sydnocarb potently (K(i) = 8.3 ± 0.7 nM) blocked recombinant human DAT expressed in Chinese hamster ovary-K1 cells and less potently blocked the norepinephrine transporter (K(i) = 10.1 ± 1.5 μM). Sydnocarb at 10 μM did not bind to 64 other targets. In rats, 10 and 30 mg/kg sydnocarb showed a 2-fold longer half-life in plasma and brain and a 5-fold lower brain-to-plasma ratio compared with 0.3 and 1 mg/kg D-AMPH. In the Irwin assay, sydnocarb was well tolerated up to 30 mg/kg; D-AMPH-like stereotypic behaviors were evident at 100 mg/kg. Behavioral effects of 30 mg/kg sydnocarb and 0.3 mg/kg D-AMPH were comparable. In a sleep/wake assay, 10 mg/kg sydnocarb and 1 mg/kg D-AMPH increased wakefulness comparably; however, sydnocarb (up to 30 mg/kg) did not induce D-AMPH-like rebound hypersomnolence (RHS). Like D-AMPH, sydnocarb enhanced theta power, an electrophysiological measure of cognitive function. In conclusion, sydnocarb is a selective and potent DAT inhibitor that produces robust increases in the wake state without RHS, and with potential cognitive-enhancing properties.

Rationale: Dopamine (DA) agonists decrease prepulse inhibition (PPI) and are widely used in translational models for the sensorimotor gating deficits in schizophrenia. Reductions in PPI induced by DA agonists are routinely reversed by antipsychotics in these translational models. Nevertheless, under conditions of low-baseline PPI, DA agonists may increase PPI in humans and experimental animals. DBA/2 mice have naturally low-baseline PPI, which as in the drug-induced translational models, is increased by antipsychotics., Objective: Determine whether DBA/2 mice respond like other models of low-baseline PPI by evaluating the effect of psychostimulants (caffeine, 30-100 mg/kg IP) and the indirect DA agonists d-amphetamine (0.3-10 mg/kg IP), methylphenidate (10-100 mg/kg IP), and sydnocarb (10-30 mg/kg IP), a selective DA transporter inhibitor on PPI. Furthermore, baseline PPI in DBA/2 mice was increased by noise exposure and the effect of d-amphetamine was assessed., Results: PPI was increased at one dose for each of the psychostimulants when baseline PPI was low in naïve DBA/2 mice. Effective doses were 3 mg/kg of d-amphetamine, 30 mg/kg of methylphenidate, 30 mg/kg of sydnocarb, and 100 mg/kg of caffeine. Higher doses of d-amphetamine (10 mg/kg) and methylphenidate (100 mg/kg IP) decreased PPI. When the baseline PPI was increased by noise exposure, 10 mg/kg of d-amphetamine only reduced PPI., Conclusion: Lower doses of psychostimulants increased PPI in naïve DBA/2 mice in a manner consistent with their naturally low-baseline PPI, and higher doses decreased PPI, consistent with effects observed in most mouse strains.

The influence of ladasten and sydnocarb on dopamine and serotonin receptors and the biosynthesis and re-uptake of dopamine and serotonin has been studied. It is established that both drugs do not produce any direct effects on dopamine D1, D2, and D3 receptors in rat striatum as well as on serotonin 5-HT1A and 5-HT2A receptors in rat frontal cortex in vitro. Ladasten in a single dose of 50 mg/kg (i.p.) stimulated ex vivo dopamine biosynthesis and release in striatum, without any influence on serotonin formation neither in striatum nor in frontal cortex. On the contrary, sydnocarb (17.5 mg/kg, i.p.) decreased the level of serotonin synthesis both in striatum and frontal cortex, while not affecting the biosynthesis of dopamine. Both ladasten and sydnocarb inhibited the active transport of dopamine in rat striatal synaptosomes at IC50 = 3.56 microM and 28.66 nM, respectively, but failed to influence the serotonin re-uptake in rat frontal cortex.

The synthesis of some 4-S-(4(1)-amino-5(1)-oxo-6(1)-substituted benzyl-4(1),5(1)-dihydro-1(1),2(1),4(1)-triazin-3-yl)mercaptoacetyl-3-arylsydnones by the reaction of 3-aryl-4-bromoacetylsydnones with 6-substituted-4-amino-3-mercapto-1,2,4-triazin-5-ones is described. The IR, (1)H NMR, mass spectra and elemental analysis characterized the newly synthesized compounds. The synthesized compounds were screened for their antimicrobial activity. All the compounds showed higher activity than that of standard drug during antimicrobial studies and the activity was comparable with the standard drug for antifungal activity.

An important antitumour effect of SYD-1 (3-[4-chloro-3-nitrophenyl]-1,2,3-oxadiazolium-5-olate) has been shown. We now report the effects of this mesoionic compound on mitochondrial metabolism. SYD-1 (1.5 micromol mg(-1) protein) dose-dependently inhibited the respiratory rate by 65% and 40% in state 3 using sodium glutamate and succinate, respectively, as substrates. Phosphorylation efficiency was depressed by SYD-1, as evidenced by stimulation of the state 4 respiratory rate, which was more accentuated with glutamate ( approximately 180%) than with succinate ( approximately 40%), with 1.5 micromol mg(-1) protein of SYD-1. As a consequence of the effects on states 3 and 4, the RCC and ADP/O ratios were lowered by SYD-1 using both substrates, although this effect was stronger with glutamate. The formation of membrane electrical potential was inhibited by approximately 50% (1.5 micromol SYD-1mg(-1) protein). SYD-1 interfered with the permeability of the inner mitochondrial membrane, as demonstrated by assays of mitochondrial swelling in the presence of sodium acetate and valinomycin +K(+). SYD-1 (1.5 micromol mg(-1) protein) inhibited glutamate completely and succinate energized-mitochondrial swelling by 80% in preparations containing sodium acetate. The swelling of de-energized mitochondria induced by K(+) and valinomycin was inhibited by 20% at all concentrations of SYD-1. An analysis of the segments of the respiratory chain suggested that the SYD-1 inhibition site goes beyond the complex I and includes complexes III and IV. Glutamate dehydrogenase was inhibited by 20% with SYD-1 (1.5 micromol mg(-1) protein). The hydrolytic activity of complex F(1)F(o) ATPase in intact mitochondria was greatly increased ( approximately 450%) in the presence of SYD-1. Our results show that SYD-1 depresses the efficiency of electron transport and oxidative phosphorylation, suggesting that these effects may be involved in its antitumoural effect.

The preparation and characterization of two vitamin E analogs-sydnonimine conjugates, delta-tocopheryloxycarbonyl-3-morpholinosydnonimine (2) and troloxoxycarbonyl-3-morpholinosydnonimine (3), in which the hydroxyl group of the tocopheryl moieties is linked via an enzymatically cleavable urethane group to the sydnone moiety is described. In the presence of porcine liver esterase, these tocopheryl-sydnonimine conjugates generated the expected antioxidant moieties, i.e., delta-tocopherol or Trolox, and were found to convert oxyhemoglobin to methemoglobin at 37 degrees C in 50 mM phosphate buffer at pH 7.4, thus providing evidence for nitric oxide release. Their potency as antioxidants was indirectly studied by associating the two products of the hydrolysis, SIN-1, and delta-tocopherol or Trolox. Our findings suggest that unlike the other members of the sydnonimine family these chromane-sydnonimine derivatives do not act as peroxynitrite donors, and require enzymatic bioactivation before nitric oxide or nitroxyl anion (NO(-)) can be released.

DJ-1 plays an important role in oxidative stress, and is involved in various neurodegenerative diseases. Accumulating evidence suggests a central role for oxidative stress in multiple sclerosis (MS). The aim of this study was to examine whether changes occur in DJ-1 expression in an animal model of MS, experimental autoimmune encephalomyelitis (EAE). We found upregulation of DJ-1 mRNA and protein expression levels in EAE and a correlation between disease severity and increased DJ-1 levels. Although DJ-1 isoforms were more alkaline in controls, in EAE, a shift was noted toward acidic isoforms. ROS induced by SIN-I exposure led to an increase in DJ-1 mRNA and protein levels in human glioma U-87 cells. Immunocytochemical staining demonstrated that DJ-1 is present both in the cytoplasm and the nuclei of these cells. This is the first report of modulation of DJ-1 expression in EAE. Upregulation of DJ-1 was noted in EAE, and similar results were observed in glioma cells exposed to ROS. In view of the accumulating evidence on the central role of oxidative stress in MS, and the importance of DJ-1 in oxidative stress management by the CNS, we believe that DJ-1 will be found to have a central role in MS.

The action of Ladasten, Sydnocarb and their combination used at doses of 10 and 20 mg/kg, produce on working ability of mice was evaluated in the swimming test. It was shown that single doses of tested drugs as compared to their combination produce more pronounced and prolonged positive action on physical work ability of animals used in the experiments.

Thermoprotector properties of a 1 : 1 combination of sydnocarb and ladasten (both in a dose of 10 or 20 mg/kg) along with its effect on the hemodynamics and respiration in experimental animals were studied. The combination of sydnocarb (20 mg/kg) and ladasten (20 mg/kg) produced a significant thermoprotector effect, enhanced the regional and local cerebral flow, and increased the respiration rate.

Dose-dependent relationship of the effects of sidnocarb and Ladasten on open field behavior and free motor activity was studied in inbred C57Bl/6 and BALB/c mice differing by emotional stress reaction phenotype. Ladasten in a dose of 10 mg/kg produced activating and anxiolytic effects on BALB/c mice in the open field test. Combined injection of Ladasten (10 mg/kg) and sidnocarb (6 or 12 mg/kg) activated animal behavior in both tests.

New sydnone derivatives bearing a substituted phenyl ring at the 3-position have been synthesized. Two separate series of 3-(carboxyphenyl)sydnone derivatives have been prepared by cyclization of the corresponding N-nitroso-N-(carboxyphenyl)-glycine 3. The obtained 3-(carboxyphenyl)sydnones 4 were subjected to a series of different chemical reactions on the carboxylic acid group. Compound 5, the potassium salt of 4a, was reacted with alpha-chloroacetanilide derivatives 6 to give the corresponding esters 7. On the other hand, the acid hydrazide 9 was condensed with different aromatic aldehydes to give the corresponding arylidene derivatives 10. The synthesized compounds were tested for their antibacterial activities against both gram-positive and gram-negative organisms. Some of the test compounds exhibited high activity; among them, 10d is considered to be a lead compound possessing high broad-spectrum antibacterial activity.

Several series of 3-phenylsydnone derivatives conjugated to well-known moieties with antibacterial activity were synthesized via several routes. These derivatives include 3-cyano-2-oxopyridine, 2-amino-3-cyanopyridine, 2-arylidene-1-ethylidenehydrazine and 2-aroyl-1-ethylidenehydrazine moieties. Thus, the key intermediate 3-(4-acetylphenyl)sydnone (3) was allowed to react with the appropriate aldehyde, ethyl cyanoacetate or malononitrile in presence of excess ammonium acetate in two steps (method 1) or through a one-pot reaction technique (methods 2 and 3) to give the corresponding sydnone derivatives 5 and 6, respectively. Moreover, condensation of compound 3 with hydrazine hydrate followed by the reaction with the appropriate aldehyde, mono- and dicarboxylic acid hydrazide yielded the corresponding sydnone derivatives 8, 9 and 10, respectively. Most of the synthesized compounds were screened for their in vitro antibacterial activity against various pathogenic organisms of both Gram-positive and Gram-negative bacteria. The minimum inhibitory concentrations (MICs) were determined using agar dilution method.

The involvement of dopamine receptors of various subtypes in the mechanisms of locomotor hyperactivity caused by single administration of psychostimulants d-amphetamine and syndnocarb was studied in C57BL mice. Administered in a dose not influencing the spontaneous locomotor activity, SCH23390 and raclopride--selective antagonists of the D1 and D2 subtypes of dopamine receptors, respectively--abolished the hyperactivity induced by d-amphetamine, while not significantly changing the effect of sydnocarb. On the contrary, clozapine--antagonist of the D4 subtype of dopamine receptors--failed to reduce the stimulant action of d-amphetamine, but significantly decreased the effect of sydnocarb under the same experimental conditions.

A series of compounds containing an N-(4'-substituted-3'-nitrophenyl)sydnone moiety with potential antitumor activity was prepared based on active analogues. The rationale behind the design of these compounds is presented along with the 4-step synthetic route to the derivatives in the 4'-position of the phenyl sydnone framework. Out of the six novel compounds, the 4'-fluoro derivative has an improved activity against all three cell lines as compared to the earlier leads.

Effects of the psychostimulants D-amphetamine and sydnocarb on the locomotor activity and c-Fos protein expression in the brain of C57BL and BALB/c mice was studied. The drugs significantly increase the locomotor activity and the level of c-Fos protein in the brain structures of both lines. The effect of D-amphetamine with respect to the locomotor activity was more pronounced in C57BL mice, which correlates with a higher level of the c-Fos expression in the secondary motor cortex. At the same time syndocarb more significantly than D-amphetamine induces expression of the c-Fos protein in the nucleus accumbens core of C57BL mice. Injection of an 0.85% NaCl solution led to a moderate increase in the locomotor activity in the mice of both lines, while the c-Fos expression in the secondary motor cortex and septum was more pronounced in C57BL than in BALB/c mice.

The neurotoxic effects of psychostimulants at high dosages limit their clinical applicability but the mechanism of neurotoxicity is still unsettled. We now studied by microdialysis how acute and subchronic (four times at 2-h intervals) administrations of D-amphetamine and sydnocarb [3-(beta-phenylisopropyl)-N-phenylcarbamoylsydnonimine], an original novel Russian psychostimulant, affected the extracellular levels of amino acids in the caudate-putamen of halothane-anesthetized male Sprague-Dawley rats. Acute D-amphetamine administration (5.0 mg/kg, i.p.) produced a moderate accumulation of extracellular glutamate and aspartate. Sydnocarb (23.8 mg/kg, i.p., a dose equimolar to 5.0 mg/kg D-amphetamine) also increased extracellular glutamate and alanine. Subchronic D-amphetamine administration (5.0 mg/kg x 4, i.p.) caused gradual fivefold increases in the glutamate and taurine levels and moderate increases in the aspartate and alanine levels. Subchronic sydnocarb administration (23.8 mg/kg x 4, i.p.) elicited a marked increase in the aspartate level and a small increase in the level of glutamate. The alanine level increased temporarily after each administration of sydnocarb, while the taurine level increased only after the last injection. We conclude that the mode of action of sydnocarb differs from that of D-amphetamine. Sydnocarb also seems to be less neurotoxic than D-amphetamine, since it elicits lesser changes in the extracellular level of glutamate.

The synthesis of some 4-(arylsydnonyl)-2-(4-arylhydrazono-3-methyl-5-oxo-2-pyrazolin-1-yl)- thiazoles by reacting 1-thiocarboxamido-3-methyl-4-(aryihydrazono)-2-pyrazolin-5-ones with different 4-bromoacetyl-3-arylsydnones is described. A few compounds from this series were screened for their anti-inflammatory, analgesic, and CNS depressant activities. Among the tested compounds 6s, 6d, 6n, and 6u showed significant anti-inflammatory activity comparable with that of standard drug Ibuprofen. Compounds containing chlorine and carboxylic substituents are more active. 6f, 6r, and 6u showed marked analgesic activity and most of the compounds tested showed promising CNS depressant activity comparable with that of standard drug pentobarbitone.

The increasing clinical importance of drug-resistant bacterial pathogens has encouraged additional microbiological and antibacterial research. New chalcone and sydnone derivatives of 4(3H)-quinazolinone were synthesized and evaluated for their antibacterial and antifungal activity. The microorganisms used were Escherichia coli ATCC 25922 as Gram-negative bacteria, Staphylococcus aureus ATCC 19433 as Gram-Positive bacteria and Candida albicans as yeast like fungi. The most potent compound was the nitroso derivative 6b, which exhibits interesting antibacterial and antifungal activities.

Microdialysis technique was used to compare the effects of four repeated intraperitoneal administrations of two psychostimulant drugs, D-amphetamine and sydnocarb, at the equimolar doses 5 and 23.8 mg/kg, respectively, on the extracellular level of dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and hydroxyl radicals (.OH) in the dorsal striatum of freely moving 3-month-old male Wistar rats 250-300 g in weight. D-amphetamine caused immediate increase of DA concentration up to 950% with quick decline towards baseline values thereafter, followed by much less increase after further injections. Sydnocarb elicited moderate elevation in DA level achieving 400% after the fourth injection. D-amphetamine induced deep decrease in DOPAC concentration, while sydnocarb caused its increase after the first and second dosing. Both drugs enhanced generation of .OH, the effect of D-amphetamine was more pronounced. D-Amphetamine induced more intensive stereotyped behavior in rats compare to sydnocarb. It is concluded that the psychostimulant action of sydnocarb is accompanied by facilitation of the central dopaminergic transmission in rat neostriatum and followed by less pronounced neurotoxic effect than that of D-amphetamine.

Objective: To assess the involvement of spinal inducible nitric oxide synthase (iNOS) in inflammation and nociception., Materials and Methods: The time course of iNOS mRNA expression in rat spinal cord and inflamed paw was assessed by means of quantitative real time RT-PCR. In addition, the effects of the iNOS inhibitor L-NIL on inflammatory paw edema and thermal hyperalgesia were studied in comparison to those of the NO-donor RE-2047. L-NIL (3, 9, 27 and 81 mg/kg) and RE-2047 (3, 9 and 27 mg/kg) or vehicle were administered orally 15 min prior to the intraplantar injection of 0.625 mg zymosan., Results: Following zymosan injection, mRNA expression of iNOS increased in the inflamed paw and spinal cord with a maximum at 2.5 and 4 h, respectively. In the spinal cord iNOS mRNA started to decline at 10 h whereas it remained at maximum in the inflamed paw up to the end of the observation period of 24 h. As expected, RE-2047 had significant pronociceptive and proinflammatory effects. L-NIL significantly reduced paw inflammation at 27 and 81 mg/kg but failed to reduce hyperalgesia at the doses tested., Conclusions: The results show that iNOS is upregulated in the inflamed tissue and spinal cord with a similar time course. The effects obtained with L-NIL suggest that iNOS differently contributes to the inflammatory and nociceptive response induced by zymosan.

It is widely accepted that peripheral injury increases spinal inducible cyclooxygenase (COX-2) expression and prostaglandin E(2) (PGE(2)) formation as key mediators of nociceptive sensitization. Here, we used inducible nitric oxide synthase (iNOS) gene-deficient (iNOS-/-) mice to determine the contribution of iNOS-derived nitric oxide (NO) to this process. iNOS-/- mice exhibited reduced thermal hyperalgesia after zymosan injection. Spinal NO and PGE(2) formation both remained at baseline levels, in contrast to wild-type (wt) mice. In wt mice reduced hyperalgesia similar to that seen in iNOS-/- mice was induced by local spinal, but not by systemic treatment with the iNOS inhibitor l-NIL, suggesting that the reduced heat sensitization in iNOS-/- mice was attributable to the lack of spinal rather than peripheral iNOS. Two additional observations indicate that the antinociceptive effects of iNOS inhibition are dependent on a loss of stimulation of PG synthesis. First, intrathecal injection of the COX inhibitor indomethacin, which exerted pronounced antinociceptive effects in wt mice, was completely ineffective in iNOS-/- mice. Second, treatment with the NO donor RE-2047 not only completely restored spinal PG production and thermal sensitization in iNOS-/- mice but also its sensitivity to indomethacin. In both types of mice induction of thermal hyperalgesia was accompanied by similar increases in COX-1 and COX-2 mRNA expression. The stimulation of PG production by NO therefore involves an increase in enzymatic activity, rather than an alteration of COX gene expression. These results indicate that NO derived from spinal iNOS acts as a fast inductor of spinal thermal hyperalgesia.

Bromantan (20 mg/kg, p.o.) and sydnocarb (10 mg/kg, p.o.) augment the efficacy of a 5-h operant activity in rats, the effect being achieved through different pathways. Sydnocarb increases the number of operant reactions and exhausts the sympathico adrenal system reserves. Bromantan favors the activity optimization by reducing the number of errors at a smaller number of operant reactions. Bromantan increases the tension of motivational component (electric pain irritation avoidance), whereas sydnocarb decreases this component of the operant behavior. None of the two drugs affects the degree of functional activation of the cardiovascular system.

The alpha-beta-unsaturated ketones of 3-arylsydnones (Ia-y) were treated with 1,2-phenylenediamine to obtain the 3-aryl-4-[2'-aryl- 2',4',6',7'-tetrahydro-(1'H)-1',5'-benzodiazepine-4'-yl]sydnones (IIa-y) in high yield. All the new compounds synthesised were screened for antibacterial and antifungal activities.

The model of static physical loading (SPL) was used to study the biochemical effects of graded static tension and potentiality for pharmacological mobilization of physical endurance with participation of male volunteers. A close pathogenetic linkage between the established metabolic effects of the model and their adaptive adequacy to the stressing factor show that there is every reason to arrange the observed shifts in a SPL syndrome. The SPL syndrome is primarily manifested by exaggerated tone of the adrenoactive structures, inhibition of insulin production by the pancreas, activation of the neuropeptide anti-stress mechanisms, predominant utilization of the lipid substrate in energy production, intensification of protein catabolism, and increase in myocyte membrane permeability due to energy deficit. The investigation demonstrated that improvement of static physical endurance can be attained with a mobilizing stimulator (sidnocarb) and a combination of sidnocarb with a nonmediatory preparation (bemytil). This pharmacological combination levels side-effects of exorbitant activation of the adrenal system. On the contrary, a metabolic vitamin-microelements complex ("cocktail C") perceivably enhances SPL endurance (sidnocarb dose was lowered in three times), possesses the stress-protective effect, the ability to moderate the intensity of free (uninvolved in phosphorylation) oxidation and to optimize energy-plastic processes with predominant utilization of the lipid substrate.

Objectives: The aim of this study was to determine whether the acute inhibition of nitric oxide (NO) synthase causes changes in cardiac substrate utilization which can be reversed by a NO donor., Methods: NO synthase was blocked by giving 30 mg/kg of nitro-L-arginine (NLA) i.v. to 15 chronically instrumented dogs. Hemodynamics and blood samples from aorta and coronary sinus were taken at control and at 1 and 2 h after NLA. In five dogs, 0.4 mg/kg of the NO donor 3754 was given i.v. 1 h after NLA. In six dogs, angiotensin II was infused over 2 h (20-40 ng/kg/min) to mimic the hemodynamic effects of NLA., Results: Two h after NLA: mean arterial pressure was 153 +/- 4 mmHg; MVO2 increased by 38%; cardiac uptake of lactate and glucose increased, respectively, from 20.0 +/- 5.0 to 41.0 +/- 9.3 mumol/min and from 1.1 +/- 0.7 to 6.8 +/- 1.5 mg/min (all P < 0.05 vs. control). Cardiac uptake of free fatty acids decreased by 43% after 1 h (P < 0.05) and returned to control values at 2 h. Cardiac respiratory quotient increased from 0.76 +/- 0.03 to 1.05 +/- 0.07, indicating a shift to carbohydrate oxidation. All these changes were reversed by the NO donor. In the dogs receiving angiotensin II infusion, MVO2 increased by 28% and lactate uptake doubled (both P < 0.05), but no other metabolic changes where observed., Conclusions: The acute inhibition of NO synthase by NLA causes a switch from fatty acids to lactate and glucose utilization by the heart which can be reversed by a NO donor, suggesting an important regulatory action of NO on cardiac metabolism.

Cytochrome P-450 (CYP) 3A2 and CYP2C11 are sources of 70 and 30%, respectively, of N-vinylprotoporphyrin IX (N-vinylPP) formation after administration of 3-[(arylthio)ethyl]sydnone (TTMS) to rats. Female rats receiving TTMS were pretreated with dexamethasone, which induces CYP3A1 preferentially to CYP3A2. The resulting 12-fold increase in N-vinylPP formation showed that CYP3A1 was also a source of N-vinylPP. Phenobarbital (PB) pretreatment, which induces CYP2B1/2 and 3A1/2 in male rats, increased N-vinylPP formation after TTMS administration. Troleandomycin, a selective CYP3A inhibitor, was unable to decrease TTMS-mediated N-vinylPP formation in PB-treated male rats, indicating that CYP2B1/2 were sources of N-vinylPP. This conclusion was supported by demonstrating a 15-fold increase in TTMSinduced N-vinylPP formation in female rats after CYP2B1/2 induction with PB pretreatment. Allylispropylacetamide (AIA) inactivates rat CYP2B1/2, 2C6, 2C7, 2C11, and 3A1/2. Troleandomycin was unable to decrease N-AIA protoporphyrin IX adduct (N-AIAPP) formation, showing that CYP3A1/2 were not susceptible to AIA-mediated N-alkylation. N-AIAPP formation in females was approximately 30% of that in males, and thus we attribute 30% of N-AIAPP formation in males to the non-gender-specific isozymes (CYP2C6, 2C7, and/or 2B1/2), whereas approximately 70% originates from CYP2C11. PB treatment in female rats resulted in a 5-fold increase in N-AIAPP formation, showing that CYP2B1/2 were also susceptible to N-alkylation mediated by AIA. 1-Aminobenzotriazole elicited formation of equivalent amounts of N'N-aryl bridged protoporphyrin IX in male and female rat liver, demonstrating that nonselective mechanism-based inactivation is accompanied by nonselective conversion of the CYP heme moieties to N'N-aryl bridged protoporphyrin IX.

After p.o. administration to rats in doses up to 30 mg/kg, Viagra showed no antithrombotic effect. However, it enhanced the inhibition of thrombus formation by RE 2047 from 9% to 17% (5 + 5 mg/kg) or 19% to 27% (10 + 10 mg/kg) in arterioles. This effect was even more obvious in venules where an inhibition of 9% (5 + 5 mg/kg) or 15% (10 + 10 mg/kg) was seen whereas the individual drugs had no effect. The antithrombotic activity of molsidomine was not altered. The blood pressure (b.p.) of spontaneously hypertensive rats was reduced by the combination of Viagra and RE 2047 (5 + 5 mg/kg) to 94% of normal after 2 h while the individual drugs had no effect at this dose. The coadminstration of 10 mg/kg of each drug reduced the b.p. to 87% of normal. The combination of Viagra with molsidomine decreased b.p. to 84% (5 + 5 mg/kg) or 79% (10 + 10 mg/kg), respectively.

Sydnocarb (3-(beta-phenylisopropyl)-N-phenylcarbamoylsydnonimine) is a psychostimulant in clinical practice in Russia as a primary and adjunct therapy for a host of psychiatric disorders, including schizophrenia and depression. It has been described as a stimulant with an addiction liability and toxicity less than that of amphetamines. The present study undertook to evaluate the psychomotor stimulant effects of sydnocarb in comparison to those of methamphetamine. Sydnocarb increased locomotor activity of mice with reduced potency (approximately 10-fold) and efficacy compared with methamphetamine. Sydnocarb blocked the locomotor depressant effects of haloperidol at doses that were inactive when given alone. The locomotor stimulant effects of both methamphetamine and sydnocarb were dose-dependently blocked by the dopamine D1 and D2 antagonists SCH 39166 and spiperone, respectively; blockade generally occurred at doses of the antagonists that did not depress locomotor activity when given alone. In mice trained to discriminate methamphetamine from saline, sydnocarb fully substituted for methamphetamine with a 9-fold lower potency. When substituted for methamphetamine under self-administration experiments in rats, 10-fold higher concentrations of sydnocarb maintained responding by its i.v. presentation. Sydnocarb engendered stereotypy in high doses with approximately a 2-fold lower potency than methamphetamine. However, sydnocarb was much less efficacious than methamphetamine in inducing stereotyped behavior. Both sydnocarb and methamphetamine increased dialysate levels of dopamine in mouse striatum; however, the potency and efficacy of sydnocarb was less than methamphetamine. The convulsive effects of cocaine were significantly enhanced by the coadministration of nontoxic doses of methamphetamine but not of sydnocarb. Taken together, the present findings indicate that sydnocarb has psychomotor stimulant effects that are shared by methamphetamine while demonstrating a reduced behavioral toxicity.

The porphyrinogenicity of 3-[(arylthio)ethyl]sydnone (TTMS) and 3, 5-diethoxycarbonyl-1,4-dihydro-2,6-dimethyl-4-ethylpyridine (4-ethylDDC) in rats is dependent on mechanism-based inactivation of selected isozymes of hepatic cytochrome P450 (P450), namely P4501A1/2, 2C6, 3A, and 2C11, followed by formation of ferrochelatase-inhibitory N-alkyl protoporphyrin IX (N-alkylPP). The objective of this study was to determine which P450 isozymes were sources of the N-alkylPPs. Previously, selective inhibition of male rat P4503A showed that it was the major source of N-vinylprotoporphyrin IX after TTMS administration. In the present study, when TTMS was administered to female rats, which lack P4503A2 and 2C11, N-vinylPP formation was 2.3% of that produced by males, which have both of these isozymes. Therefore, although P4503A2 is a major source, P4502C11 is also a significant source of N-vinylPP in males. Selective inhibition of P4503A and 1A1/2 did not decrease N-ethylPP formation in response to 4-ethylDDC administration to male rats, showing that P4503A and 1A1/2 were not sources of N-ethylPP. Thus P4502C6 and 2C11 were the remaining isozyme candidates to be investigated. When 4-ethylDDC was administered to female rats, N-ethylPP formation was 22% of that produced by males. Because female rat livers contain P4502C6 but lack the male specific P4502C11, the likely origin of N-ethylPP in females is P4502C6. Because males produced markedly more N-ethylPP than females, and males have P4502C11 in addition to P4502C6, we conclude that P4502C11 is the major source of N-ethylPP in males, whereas P4502C6 may also be a significant contributor.

Transcerebral microdialysis was used to evaluate the effect of a psychostimulant drug, sydnocarb (3-(beta-phenylisopropyl)-N-phenylcarbamoylsydnonimine), on the extracellular levels of dopamine, 3,4-dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the dorsal striatum and nucleus accumbens of freely moving rats. Sydnocarb dose dependently (4.4, 8.75 and 17.5 mg/kg, i.p.) induced a relatively modest (up to 350% of control) and long-lasting (up to 6 h) increase in dopamine extracellular level in the rat dorsal striatum. The drug at 8.75 mg/kg, i.p., produced an approximately similar increase in dopamine efflux in the dorsal striatum and in the nucleus accumbens of freely moving rats. Sydnocarb had no effect on DOPAC or HVA extracellular levels in the rat basal ganglia in vivo at any dose studied. It is important that the drug increased the efflux of dopamine in a tetrodotoxin-sensitive and Ca2+-dependent manner. Measurements of behavioral parameters in non-operated rats revealed that sydnocarb markedly increased locomotor activity and induced stereotyped behavior. These data suggest that the stimulant action of sydnocarb is accompanied by a facilitation of central dopaminergic transmission involving an increase in Ca2+-dependent vesicular dopamine efflux.

We have used a yeast p53 functional assay to study induction of mutations in the p53 tumor suppressor gene by nitric oxide and cytosine methylation. The yeast assay identifies only biologically important p53 mutations. p53 cDNA was treated with the nitric oxide donor sydnonimine, PCR-amplified and transfected into yeast. Sydnonimine produced a significant, dose-dependent increase in C:G-->A:T transversions. Many important p53 mutational hotspots are postulated to arise by deamination of methylCpG in tumors. We therefore examined nitric oxide induction of mutations in p53 cDNA methylated by PCR-mediated substitution of 5-methylcytosine for cytosine or by treatment with the SssI CpG methylase. Both methylation procedures increased the baseline mutation rate, and nitric oxide treatment produced a further increase in mutation yield. Sequence analysis showed that methylation alone led to C:G-->T:A transitions, whereas nitric oxide treatment simply produced more C:G-->A:T transversions. Thus the most important factor in C:G-->T:A transition at CpG sites identified in this experimental system is cytosine methylation, consistent with spontaneous conversion of 5-methylcytosine to thymine by deamination.

The influence of endogenous nitric oxide (NO) and NO-releasing compounds on free radical release from porcine leukocytes was investigated by luminol-enhanced chemiluminescence (CL). The direct free radical-scavenging activity of the compounds was determined by a cell-free system using xanthine plus xanthine oxidase (X + XO). The NO donor, N-(2-hydroxyethyl)nicotinumide nitrate (nicorandil), markedly inhibited CL generated by phorbol myristate acetate (PMA)-stimulated leukocytes. In addition, nicorandil and S-nitrozo-N-acetylpenicillamine (SNAP) both decreased CL generated by X + XO. Conversely, C87 3754, a NO-releasing sydnonimine, decreased free radical release from leukocytes only when preincubated with the cells and had no effects on the X + XO system. None of the NO donors inhibited peroxynitrite-generated CL. L-, but not D-, arginine inhibited PMA-activated free radical generation without affecting X + XO-induced CL. L-Canavanine, N omega-nitro-L-arginine (L-NNA), and L-nitro-arginine methyl ester (L-NAME), inhibitors of the NO pathway, augmented PMA-induced CL. However, L-canavanine, but not L-NNA and L-NAME, produced a significant inhibition of X + XO-induced CL. It is concluded that endogenous NO may play an important role in the measurement of free radicals released from porcine leukocytes, assessed by luminol-enhanced CL, and that compounds with NO-releasing properties decrease CL, possibly by interfering with free radical generation.

The mechanisms governing the pathological accumulation of collagen in the extracellular matrix following angioplasty are complex, but may involve interactions between endothelium-derived paracrine agents and vascular cellular components. We tested the hypothesis that nitric oxide (NO) directly decreases collagen levels and decreases endothelin (ET-1)-stimulated increases in levels of specific collagen subtypes in coronary vascular smooth muscle cells (VSMC). Cultured VSMC were incubated for 48 h with the NO donor CAS 754 (10(-4) M), ET-1 (10(-8) M), or ET-1 plus CAS 754. In some experiments, angiotensin II (Ang II; 10(-8) M) was utilized in place of ET-1. Soluble collagen types I and III were quantitated with an ELISA method, and cell counts were performed. CAS 754 significantly inhibited cell proliferation (-17+/-2% v control), basal total protein synthesis (-65+/-7% v control), and basal collagen type I levels (-39+/-6% v control), but not collagen type III levels. ET-1 and Ang II both significantly stimulated cell proliferation (26+/-5% v control), total protein synthesis (169+/-6% v control), and collagen type I levels (200+/-11% v control). Ang II, but not ET-1, significantly increased collagen type III levels. Co-incubations of ET-1 and CAS 754 resulted in a significant decrease in cell proliferation, protein synthesis, and collagen levels (-23+/-2% v control, 90+/-5% v control, and 63+/-3% v control, respectively) compared to ET-1 alone. In contrast, co-incubation of Ang II and CAS 754 had no significant effect on cell proliferation, protein synthesis, and collagen levels seen with Ang II alone. These results demonstrate that NO inhibits basal collagen levels and cell division. Additionally, NO alters ET-1 stimulation of VSMC proliferation, protein synthesis, and production of extracellular matrix components. Thus, an imbalance in key endothelium-derived compounds could significantly impact upon extracellular matrix deposition following mechanical revascularization.

A number of xenobiotics are known to exert their porphyrinogenic effects in rodents and chick embryos through mechanism-based inactivation of certain cytochrome P450 (P450) isozymes. To facilitate the extrapolation of results from test animals to humans, we have assessed the ability of three prototype porphyrinogenic compounds-namely, 3,5-diethoxycarbonyl-1,4-dihydro-2,6-dimethyl-4-ethylpyridine (DDEP), 3-[2-(2,4,6-trimethylphenyl)thioethyl]-4-methylsydnone (TTMS), and allylisopropylacetamide (AIA)-to cause mechanism-based inactivation of cDNA-expressed human P450s 1A1, 1A2, 2C9-Arg144 (2C9), 2D6-Val374 (2D6), and 3A4 in microsomes from human lymphoblastoid cell lines (Gentest Corp., Woburn, MA). The following catalytic markers of human P450 isozymes were used: ethoxyresorufin O-deethylase (P450s 1A1 and 1A2), diclofenac 4-hydroxylation (P4502C9), dextromethorphan O-demethylase (P4502D6), and testosterone 6 beta-hydroxylation (P4503A4). We found that DDEP and TTMS caused mechanism-based inactivation of cDNA-expressed human P450s 1A1, 1A2, and 3A4, whereas only DDEP was able to cause mechanism-based inactivation of cDNA-expressed human P4502C9; neither xenobiotic caused mechanism-based inactivation of cDNA-expressed human P4502D6. A comparison of the human P450 isozyme data with results previously obtained in rat and chick embryo liver showed a close correspondence between the results obtained with P450s 1A and 3A, but not the P4502C subfamily. Because several rat isozymes (P450s 2A1, 2B1, 2C6, 2C11, and 3A1) undergo inactivation by AIA, it was noteworthy that AIA did not inactivate any of the cDNA-expressed human P450 isozymes. Because mechanism-based inactivation of P450 isozymes is related to the porphyrinogenicity of xenobiotics, our results demonstrate the importance of supplementing studies of mechanism-based inactivation of P450 isozymes in animal models with similar studies on cDNA-expressed human P450 isozymes.

The effect of a nitric oxide (NO) donor and the influence of endogenous NO in modulating ischaemia-induced arrhythmias was assessed in anaesthetised rats. The nitric oxide donor C87-3754 (1 mg/kg) caused a significant reduction in arterial blood pressure before coronary artery ligation but did not influence the incidence or severity of ventricular arrhythmias during a 30-min period of myocardial ischaemia [60 and 58% incidence of ventricular fibrillation (VF) in control and treated rats, respectively]. When the hearts were preconditioned by a short (3 min) coronary artery occlusion before the 30-min period of ischaemia, there was a marked reduction in both the number of ventricular ectopic beats (260 +/- 65 vs. 812 +/- 256 beats/min in controls; p < 0.05) and the incidence of ventricular fibrillation (9 vs. 67% in controls; p < 0.05). Neither NG-nitro-L-arginine methyl ester (L-NAME; 10-100 mg/kg) nor methylene blue (1-50 mg/kg) attenuated this marked antiarrhythmic effect of preconditioning. L-NAME caused a significant increase in blood pressure with all doses used, whereas methylene blue did not increase blood pressure. Both L-NAME and methylene blue attenuated ventricular arrhythmias in non-preconditioned hearts. L-NAME reduced the number of ventricular ectopic beats (from 812 +/- 256 to 318 +/- 81 beats/min at 10 mg/kg; p < 0.05), whereas methylene blue decreased the incidence of VF from 67 to 20% at a dose of 50 mg/kg (p < 0.05). These findings suggest that neither endogenous nor exogenously administered NO reduces ischaemic arrhythmias in anaesthetised rats. Furthermore, the antiarrhythmic effect of preconditioning in this species appears to be independent of NO. The antiarrhythmic effects seen with both methylene blue and L-NAME may be the result of actions other than inhibition of the production or actions of NO.

We performed this study to evaluate the effects of changing the level of nitric oxide (NO) on disruption of the blood-brain barrier (BBB) by hyperosmolar mannitol. Under isoflurane anesthesia, control rats (control group, n = 6) were given infusions with 25% mannitol into the internal carotid artery before measuring the transfer coefficient (Ki) of 14C-alpha-aminoisobutyric acid (14C-AIB). In the CAS group (n = 6), [3-(cis-2,6-dimethyl piperidino)-sydnonimine] (CAS 754), a NO donor, was injected to decrease the mean arterial pressure (MAP) to 55 mm Hg and in the L-NAME group (n = 6), NG-nitro-L-arginine methyl ester (L-NAME), a NO synthase inhibitor, was injected before administering mannitol. In additional control animals (control + P group, n = 6) and additional CAS 754-treated animals (CAS + P group, n = 6), phenylephrine was infused to keep MAP at 130 mm Hg during the experimental period. In the control group, with mannitol injection, the Ki of the ipsilateral cortex (IC) where mannitol was injected increased to 4.3 times that of the contralateral cortex (CC) (17.2 +/- 2.9 vs 4.0 +/- 2.6 microliters.g-1.min.1). Without blood pressure control, the Ki of the IC of the CAS group (7.0 +/- 4.5) was lower and that of the L-NAME group (26.2 +/- 12.7) was higher than that of the control animals. At the same MAP, the Ki of the IC of the CAS + P group (9.6 +/- 3.1) was significantly lower than that of the control + P group (21.3 +/- 14.5) or that of the L-NAME group. There was no significant difference in the Ki of the IC between the control + P and the L-NAME groups. In conclusion, L-NAME worsened BBB disruption induced by hyperosmolar solution, which may be due to the pressure effect of L-NAME. CAS 754 was effective in attenuating disruption of the BBB caused by hyperosmolar mannitol. This effect is apparently not due to decreased MAP.