Modulation of aryl hydrocarbon receptor‐regulated genes by acute administration of ammonium metavanadate in kidney,lung and heart of C57BL/6 mice

We recently reported that vanadium (V⁵⁺) was able to decrease the 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD)‐mediated induction of Cyp1a1 and Nqo1 at mRNA, protein and catalytic activity levels in mouse hepatoma Hepa 1c1c7 and human hepatoma HepG2 cells. However, little is known regarding the in vivo effects. Thus, the objective of this study was to investigate whether similar effects would occur at the in vivo level. Therefore, we examined the effect of exposure to V⁵⁺ (5 mg kg^?1) with or without TCDD (15 µg kg^?1) on the AhR‐regulated genes in kidney, lung and heart of C57BL/6 J mice. Our results demonstrated that V⁵⁺ alone significantly decreased Cyp1b1 protein and catalytic activity levels in kidney at 24 h. Moreover, it significantly potentiated Nqo1 and Gsta1 gene expression in the heart, and only Gsta1 gene expression in the lung. Upon co‐exposure, we found that V⁵⁺significantly inhibited the TCDD‐mediated induction of Cyp1a1, Cyp1a2 and Cyp1b1 mRNA, protein and catalytic activity levels in the kidney at 24 h. On the other hand, V⁵⁺ significantly potentiated the TCDD‐mediated induction of Nqo1 and Gsta1 protein and activity levels in the kidney. Cyp1a1, Cyp1b1, Nqo1 mRNA, protein and catalytic activity levels in the lung were significantly potentiated at 6 h. Interestingly, all tested genes in the heart were significantly decreased at 6 h with the exception of Gsta1 mRNA. The present study demonstrates that V⁵⁺ modulates TCDD‐induced AhR‐regulated genes. Furthermore, the effect on one of these enzymes could not be generalized to other enzymes even if it was in the same organ. Copyright © 2012 John Wiley & Sons, Ltd.     

Dimethylarsinic acid modulates the aryl hydrocarbon receptor-regulated genes in C57BL/6 mice: in vivo study

1.?Dimethylarsinic acid (DMA(V)) is the major metabolite of inorganic arsenic in human body. Thus we investigated the effect of DMA(V) on the alteration of phase I (typified by Cyp1a) and phase II (typified by Nqo1) AhR-regulated genes in vivo. C57BL/6 mice received DMA(V) (13.3?mg/kg, i.p.) with or without TCDD (15?μg/kg, i.p.), thereafter the liver, lung, and kidney were harvested at 6 and 24?h post-treatment.

2.?Results demonstrated that DMA(V) has no significant effect on Cyp1a mRNA and protein expression or catalytic activity in the liver. On the other hand, DMA(V) significantly potentiated the TCDD-mediated induction of Cyp1a mRNA and protein expression, with a subsequent potentiation of catalytic activity in the lung. Moreover, DMA(V) significantly inhibited the TCDD-mediated induction of Cyp1a mRNA and protein expression with subsequent inhibition of catalytic activity in the kidney.

3.?Regarding to phase II AhR-regulated genes, DMA(V) has no significant effect on Nqo1 mRNA and protein expression, or activity neither in the liver, lung, or kidney.

4.?In conclusion, the present work demonstrates for the first time that DMA(V) modulates AhR-regulated genes in a tissue- and enzyme-specific manner. This modulation may play a crucial role in arsenic-induced toxicity and carcinogenicity.     

Differential modulation of aryl hydrocarbon receptor regulated enzymes by arsenite in the kidney, lung, and heart of C57BL/6 mice

During the last couple of decades, efforts have been made to study the toxic effects of individual aryl hydrocarbon receptors (AhR) ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or heavy metals typified by arsenic As(III). However, little is known about the combined toxic effects of TCDD and As(III) in vivo. Previous reports from our laboratory and others have demonstrated that As(III), by itself or in the presence of AhR ligands, such as TCDD, is capable of differentially altering the expression of various phase I and phase II AhR-regulated genes in in vitro systems. Thus, the objective of the current study was to investigate whether or not similar effects would occur at the in vivo level. Therefore, we examined the effect of exposure to As(III) (12.5 mg/kg) in the absence and presence of TCDD (15 μg/kg) on the AhR-regulated genes using C57Bl/6 mice. Our results demonstrated that As(III) alone inhibited Cyp1a1 and Cyp1a2 in the kidney, while it induced their levels in the lung and did not affect their mRNA levels in the heart. As(III) also induced Nqo1 and Gsta1 in all tested tissues. Upon co-exposure to As(III) and TCDD, As(III) inhibited the TCDD-mediated induction of Cyp1a1 in the kidney and heart, Cyp1a2 in the kidney and heart, while it potentiated TCDD-mediated induction of Cyp1a1 in the lung, and Nqo1 and Gsta1 in the kidney and lung. In conclusion, the present study demonstrates for the first time that As(III) modulates constitutive and TCDD-induced AhR-regulated genes in a time-, tissue-, and AhR-regulated enzyme-specific manner.     

Effect of mercury on aryl hydrocarbon receptor-regulated genes in the extrahepatic tissues of C57BL/6 mice

The individual toxic effects of aryl hydrocarbon receptors (AhR) ligands such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) or heavy metals typified by mercury (Hg²⁺) has been previously demonstrated. However, little is known about the combined toxic effects of TCDD and Hg²⁺in vivo. Therefore, we examined the effect of exposure to Hg²⁺ (2.5 mg/kg) in the absence and presence of TCDD (15 μg/kg) on the AhR-regulated genes using C57Bl/6 mice. Hg²⁺ alone did not affect kidney, lung, or heart Cyp1a1/1a2/1b1 mRNA levels. On the contrary, Hg²⁺ alone significantly induced kidney Cyp1a1/1a2/1b1 and lung Cyp1b1 protein and catalytic activities. Hg²⁺ also induced Nqo1, Gsta1, and HO-1 at the mRNA, protein, and activity levels in the kidney and heart but not in the lung. Upon co-exposure to Hg²⁺ and TCDD, Hg²⁺ significantly potentiated the TCDD-mediated induction of kidney and lung Cyp1a1/1a2/1b1 mRNA levels, while it decreased their kidney protein and catalytic activity and it increased their lung protein. In addition, Hg²⁺ potentiated the TCDD-mediated induction of Nqo1, Gsta1, and HO-1 at mRNA, protein and activity levels in all tissues. The present study demonstrates that Hg²⁺ modulates the constitutive and TCDD-induced AhR-regulated genes in a time-, tissue- and, AhR-regulated enzyme genes manner.     

Modulation of ethanol drinking-in-the-dark by mecamylamine and nicotinic acetylcholine receptor agonists in C57BL/6J mice

Rationale  Recent reports describe a restricted access ethanol consumption paradigm where C57Bl/6J mice drink until intoxicated. Termed “drinking in the dark” (DID), this paradigm has been used as a model of binge drinking. Although neuronal nicotinic acetylcholine receptors (nAChRs) have been implicated in alcohol drinking in rats pre-trained to self-administer ethanol, their role in binge-like ethanol consumption is unknown. Objectives  To determine if nAChRs are involved in binge drinking as measured by the DID assay in C57Bl/6J mice. Materials and methods  Adult male C57Bl/6J mice were injected i.p. with nicotinic receptor antagonists including mecamylamine, hexamethonium, dihydro-β-erythroidine, and methyllycaconitine. Immediately following injection, mice were presented with 20% ethanol for 2 h in the DID assay to measure ethanol consumption. Nicotinic agonists including cytisine and nicotine were also evaluated. The effects of mecamylamine and nicotine on ethanol-induced dopaminergic neuronal activation in the VTA were evaluated via immunohistochemistry. Results  Mecamylamine dose dependently reduced ethanol consumption; whereas, the peripheral antagonist hexamethonium had no significant effect. Nicotinic agonists, cytisine and nicotine, reduced ethanol consumption. None of the effective nicotinic receptor drugs reduced sucrose drinking. Mecamylamine blocked ethanol activation of dopaminergic neurons while nicotine alone activated them without additional activation by ethanol. Conclusions  Neuronal nAChRs are involved in ethanol consumption in the DID paradigm. The effects of mecamylamine, nicotine, and cytisine on ethanol intake appear to be specific because they do not reduce sucrose drinking. Mecamylamine reduces alcohol consumption by blocking activation of dopaminergic neurons; whereas, nicotinic agonists may activate the same reward pathway as alcohol.     

Structure-dependent induction of aryl hydrocarbon hydroxylase activity in C57BL/6 mice by 2,3,7,8-tetrachlorodibenzo-p-dioxin and related congeners: mechanistic studies

The time- and dose-dependent induction of murine hepatic microsomal aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin O-deethylase (EROD) activities by five polychlorinated dibenzo-p-dioxin and dibenzofuran congeners showed that the order of induction potency was 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) greater than 2,3,7,8-tetrachlorodibenzofuran (TCDF) greater than 1,2,3,7,8-pentachlorodibenzo-p-dioxin (PCDD) greater than 1,2,3,7,8-pentachlorodibenzofuran (PCDF) greater than 2,3,7-trichlorodibenzo-p-dioxin (TrCDD). These structure-induction relationships were comparable to the structure-toxicity and competitive structure-receptor binding relationships previously reported for these compounds. However, using the corresponding radiolabeled congeners, the direct binding Kd values for dissociation of the cytosolic receptor-ligand complexes were 9.52, 7.96, 1.27, 3.10, and 8.31 nM for the 2,3,7,8-TCDD, 2,3,7,8-TCDF, 2,3,7-TrCDD, 1,2,3,7,8-PCDD, and 1,2,3,7,8-PCDF congeners and these data were clearly not structure dependent (i.e., similar to the structure-activity relationships). Some of the molecular properties for several radioligand-receptor complexes were similar; for example, the sedimentation coefficients for the cytosolic and nuclear receptor complexes varied from 8.8-10.4 S and 5.98-7.0 S, respectively, and the nuclear receptor complexes for all the radioligands eluted from a DNA-Sepharose column at salt concentrations of 0.27-0.29 M. Treatment of the mice with a maximum inducing dose of 2,3,7,8-[3H]TCDD resulted in a time-dependent formation of the nuclear receptor complex which was maximized between 16-24 hr and subsequently decreased up to 72 hr after initial exposure. In parallel studies, the nuclear receptor complex levels were determined 16 hr after treatment of the mice with different doses (2.25, 4.5, and 45 micrograms/kg) of all five radioligands. The results showed that at submaximal induction of the monooxygenase enzyme activities there was a linear correlation between the induced AHH or EROD activities (after 32 hr) and the corresponding nuclear receptor complex levels. It was also apparent from the data that the relative levels of nuclear receptor complex were structure dependent and this suggests that the transformation or activation of cytosolic receptor complexes may be a ligand structure-dependent process which correlates with the observed structure-activity relationships for 2,3,7,8-TCDD and related compounds.     

Effects of acute alcohol administration on object recognition learning in C57BL/6J mice.

The goal of the present study was to investigate effects of alcohol intoxication on the object recognition learning task. Male C57BL/6J mice habituated to saline injections and exploratory arena received different doses of ethanol (0, 1.6 or 2.4 g/kg) before or after a 10-min training session. During training, animals were exposed to a small object (a marble or a die). On the next day, during a 10-min testing session, animals were exposed to two objects: the familiar object from the previous day and a novel object. Analysis of behavior during testing showed that mice injected with 0 and 1.6 g/kg of ethanol before training spent more time exploring a novel than a familiar object during testing. In contrast, mice injected with 2.4 g/kg ethanol spent equal amounts of time exploring the novel and the familiar object. Mice injected with this dose of ethanol after training did not show a decreased ratio of object exploration during testing. Analysis of behavior during training showed that mice injected with this dose of ethanol spent less time exploring the object, although their locomotor activity was not decreased. Our results show that in C57BL/6J mice, ethanol intoxication interferes with exploratory activity during object exploration, but not with consolidation of memory.     

Increased accumulation of neutrophils and decreased fibrosis in the lung of NADPH oxidase-deficient C57BL/6 mice exposed to carbon nanotubes

Single-walled carbon nanotubes (SWCNT) have been introduced into a large number of new technologies and consumer products. The combination of their exceptional features with very broad applications raised concerns regarding their potential health effects. The prime target for SWCNT toxicity is believed to be the lung where exposure may occur through inhalation, particularly in occupational settings. Our previous work has demonstrated that SWCNT cause robust inflammatory responses in rodents with very early termination of the acute phase and rapid onset of chronic fibrosis. Timely elimination of polymorphonuclear neutrophils (PMNs) through apoptosis and their subsequent clearance by macrophages is a necessary stage in the resolution of pulmonary inflammation whereby NADPH oxidase contributes to control of apoptotic cell death and clearance of PMNs. Thus, we hypothesized that NADPH oxidase may be an important regulator of the transition from the acute inflammation to the chronic fibrotic stage in response to SWCNT. To experimentally address the hypothesis, we employed NADPH oxidase-deficient mice which lack the gp91^phox subunit of the enzymatic complex. We found that NADPH oxidase null mice responded to SWCNT exposure with a marked accumulation of PMNs and elevated levels of apoptotic cells in the lungs, production of pro-inflammatory cytokines, decreased production of the anti-inflammatory and pro-fibrotic cytokine, TGF-β, and significantly lower levels of collagen deposition, as compared to C57BL/6 control mice. These results demonstrate a role for NADPH oxidase-derived reactive oxygen species in determining course of pulmonary response to SWCNT.     

Acute lung injury induced by chlorine inhalation in C57BL/6 and FVB/N mice

Humans may be exposed to chlorine gas via accidental or intentional release, and effective countermeasures for the resulting lung injury are lacking. To develop a model in which therapeutic measures could be evaluated, lung injury induced by chlorine inhalation in two inbred mouse strains was examined. C57BL/6 and FVB/N mice were exposed for 1.1 h to varying doses of chlorine (197-289 ppm-h) and were evaluated for indices of lung injury at different times after exposure (6-48 h). Chlorine induced increases in lung weight that were more evident in FVB/N mice than in C57BL/6 mice. Both strains exhibited sloughing of airway epithelium observed within 6 h after exposure. As judged by Ly-6G immunostaining, chlorine exposure caused widespread neutrophil influx into the lung parenchyma at 6 h followed by a clustering of neutrophils around damaged airways by 24 h. High levels of cellular proliferation revealed by Ki-67 staining were observed in airway epithelium 48 h after exposure. Lavage fluid parameters showed consistent trends in both strains. Lavage fluid protein content was elevated throughout the times examined. Lavage fluid neutrophils were significantly increased beginning 12 h after exposure and were highest at 48 h. The concentration of the neutrophil chemoattractant KC peaked 6 h after exposure and was near baseline by 48 h. In summary, chlorine inhalation resulted in lung injury characterized by edema, epithelial cell death, and neutrophilic inflammation in C57BL/6 and FVB/N mice. Characterization of such responses in these mice will allow testing of therapeutic agents to treat chlorine-induced lung injury.     

Effects of aryl hydrocarbon receptor null mutation and in utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin exposure on prostate and seminal vesicle development in C57BL/6 mice.

Experiments were conducted to determine the effects of aryl hydrocarbon receptor (AhR) null mutation and in utero and lactational 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure, alone and in combination, on prostate and seminal vesicle development in C57BL/6 mice. AhR heterozygous (Ahr+/-) mice were mated, and pregnant females were dosed orally on gestation day 13 with TCDD (5 microg/kg) or vehicle. Pups underwent necropsy on postnatal days (PNDs) 35 and 90. Comparison of vehicle-exposed AhR knockout (AhRKO;Ahr-/-) with wild-type (Ahr+/+) pups revealed that the AhR is necessary for normal dorsolateral prostate, anterior prostate, and seminal vesicle development but apparently not for ventral prostate development. In wild-type mice,in utero and lactational TCDD exposure reduced ventral prostate weight by 79-87% and mRNA expression for its major androgen-dependent secretory protein (MP25) by 99%. Yet high levels of mRNA for a secretory protein normally produced primarily by the lateral prostate (PSP94) were expressed. These effects were predominantly AhR dependent because TCDD had little if any effect in AhRKO mice. TCDD reduced dorsolateral prostate weight in wild-type but not AhRKO mice and had no significant effect on expression of mRNA for PSP94 or for probasin, a major androgen-dependent secretory protein. The PSP94 results suggest that TCDD may have caused a respecification of prostatic gene expression. TCDD reduced anterior prostate weight by more than half, and expression of mRNA for its major androgen-dependent secretory protein (renin-1) was greatly reduced. These effects were AhR dependent. Seminal vesicle weight was reduced by TCDD in wild-type mice but was increased in AhRKO mice on PND 35 and decreased on PND 90 (relative weight only). Androgen receptor mRNA levels were not significantly altered in any prostate lobe, and all organs appeared histologically normal in all groups. Serum testosterone concentrations were unchanged, and modest reductions in serum 5alpha-androstane-3alpha,17beta-diol concentrations could not account for the effects on sex organs. Collectively, these results indicate that the AhR signaling pathway plays a role in normal accessory sex organ development and thatin utero and lactational TCDD exposure disrupts development of these organs via spatially and perhaps temporally specific mechanisms.     

Ontogenic variation in acute lethality of cadmium in C57BL/6J mice

Susceptibility of C57BL/6J mice to the lethal effects of parenterally administered Cd declined as a function of age at exposure. The 7-day LD50 increased from 1.65 mg Cd/kg body wt in 7-day-old mice to 4.08 mg/kg in adult mice. Survival time following treatment with Cd also increased as a function of age. High constitutive concentrations of metallothionein, a transition metal-binding protein, in livers of young mice did not protect against the lethality of Cd. These results suggest that, in the mouse, the interaction between Cd and this metal-binding protein may be affected by age at exposure to this toxic metal.     

Metabolic and neurologic consequences of chronic lopinavir/ritonavir administration to C57BL/6 mice

It is well established that HIV antiretroviral drugs, particularly protease inhibitors, frequently elicit a metabolic syndrome that may include hyperlipidemia, lipodystrophy, and insulin resistance. Metabolic dysfunction in non-HIV-infected subjects has been repeatedly associated with cognitive impairment in epidemiological and experimental studies, but it is not yet understood if antiretroviral therapy-induced metabolic syndrome might contribute to HIV-associated neurologic decline. To determine if protease inhibitor-induced metabolic dysfunction in mice is accompanied by adverse neurologic effects, C57BL/6 mice were given combined lopinavir/ritonavir (50/12.5-200/50 mg/kg) daily for 3 weeks. Data show that lopinavir/ritonavir administration caused significant metabolic derangement, including alterations in body weight and fat mass, as well as dose-dependent patterns of hyperlipidemia, hypoadiponectinemia, hypoleptinemia, and hyperinsulinemia. Evaluation of neurologic function revealed that even the lowest dose of lopinavir/ritonavir caused significant cognitive impairment assessed in multi-unit T-maze, but did not affect motor functions assessed as rotarod performance. Collectively, our results indicate that repeated lopinavir/ritonavir administration produces cognitive as well as metabolic impairments, and suggest that the development of selective aspects of metabolic syndrome in HIV patients could contribute to HIV-associated neurocognitive disorders.     

Metabolic and neurologic consequences of chronic lopinavir/ritonavir administration to C57BL/6 mice

It is well established that HIV antiretroviral drugs, particularly protease inhibitors, frequently elicit a metabolic syndrome that may include hyperlipidemia, lipodystrophy, and insulin resistance. Metabolic dysfunction in non-HIV-infected subjects has been repeatedly associated with cognitive impairment in epidemiological and experimental studies, but it is not yet understood if antiretroviral therapy-induced metabolic syndrome might contribute to HIV-associated neurologic decline. To determine if protease inhibitor-induced metabolic dysfunction in mice is accompanied by adverse neurologic effects, C57BL/6 mice were given combined lopinavir/ritonavir (50/12.5–200/50 mg/kg) daily for 3 weeks. Data show that lopinavir/ritonavir administration caused significant metabolic derangement, including alterations in body weight and fat mass, as well as dose-dependent patterns of hyperlipidemia, hypoadiponectinemia, hypoleptinemia, and hyperinsulinemia. Evaluation of neurologic function revealed that even the lowest dose of lopinavir/ritonavir caused significant cognitive impairment assessed in multi-unit T-maze, but did not affect motor functions assessed as rotarod performance. Collectively, our results indicate that repeated lopinavir/ritonavir administration produces cognitive as well as metabolic impairments, and suggest that the development of selective aspects of metabolic syndrome in HIV patients could contribute to HIV-associated neurocognitive disorders.     

Comparison of kidney, lung and liver coumarin 7-hydroxylases in phenobarbital pretreated DBA/2J and C57BL/6J mice

In this paper we describe catalytic and immunological properties of coumarin 7-hydroxylase, a cytochrome P-450 dependent enzyme activity, in the liver, kidney and lung of C57BL/67 and DBA/2J mice. Coumarin 7-hydroxylase activity was higher in D2 than in B6 mice in all three organs. For both strains of mice, liver had the highest enzyme activity when expressed per milligram of microsomal protein. However, when expressed per nmole cytochrome P-450 there was no difference in the enzyme activity between the tissues. Inhibition of microsomal coumarin 7-hydroxylase by antibodies previously developed in our laboratory against a cytochrome P-450 fraction from D2 and B6 mouse liver, associated with coumarin 7-hydroxylase, occurred as follows. In D2 mice both antibodies caused approximately 50% inhibition of the enzyme activity of all three organs. In B6 mice, however, the only organ where considerable inhibition took place was the liver, and only when antibody against B6 cytochrome P-450 was used. Ouchterlony immunodiffusion analysis revealed a 100% crossreactivity between the two strains of mice when similar organs were compared. The 100% crossreactivity was also found between the liver and lung in both strains of mice. However, only a 50% crossreactivity was found between kidney and liver or kidney and lung in B6 and between the kidney and lung in D2. The data demonstrate interorgan and interstrain differences in the immunological and catalytical properties of cytochrome(s) P-450 catalysing coumarin 7-hydroxylation.     

Sodium thiosulphate attenuates brain inflammation induced by systemic lipopolysaccharide administration in C57BL/6J mice

It has been demonstrated that peripheral infections accompanied by neuroinflammation may modify brain development or affect normal brain aging and represent major risk factors for the development of neurological disorders. A wide range of synthetic and natural compounds with anti-inflammatory properties have been evaluated in animal models of neuroinflammation and neurodegeneration as an adjuvant therapeutic strategy. In the present study we have demonstrated for the first time that sodium thiosulphate (STS), a known antidote approved for treatment of certain medical conditions, is capable of reducing brain inflammation caused by systemic LPS administration. STS reduced brain levels of pro-inflammatory cytokine interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2), ionized calcium binding adaptor molecule 1 (Iba-1) and 18 kDa translocator protein (TSPO) in an animal model of systemic LPS-induced neuroinflammation. In addition, we demonstrated for the first time elevated TSPO expression in retinal ganglion cells layer after peripheral LPS challenge and inhibition of ocular TSPO expression after treatment with STS. We think that STS may be used as an adjuvant anti-inflammatory therapy for many pathological conditions associated with inflammation in the brain.     

Dextran sulfate sodium-induced acute experimental colitis in C57BL/6 mice is mitigated by selenium

BackgroundSodium selenite has been shown to have a protective role in experimental colitis. Th1 and Th17 responses are involved in the pathogenesis of dextran sulfate sodium (DSS)-induced colitis and inflammatory bowel disease. This study investigated whether sodium selenite can suppress Th1/Th17-mediated experimental colitis.MethodsMice were administered sodium selenite (2 μg/g body weight) by gavage daily for 30 days. Beginning on day 21, mice were administered 2.5% oral DSS for 9 days. The mice were sacrificed on day 31. Survival rates, clinical symptoms, colon lengths, and histological changes were determined.ResultsPretreatment with sodium selenite (2 μg/g body weight) improved survival rates, colon shortening, body weight loss, disease activity index, and histopathological score in mice with DSS-induced colitis. Pretreatment with sodium selenite restored interleukin-10 and Foxp3 excretion, as well as reducing the levels of interferon-γ and interleukin-17A.ConclusionsPretreatment with sodium selenite showed therapeutic potential for preventing colitis in mice. This effect may be mediated by the immunomodulation of regulatory T cells, expressing anti-inflammatory genes that suppress Th1 and Th17 responses.     

Ethanol-induced locomotor stimulation in C57BL/6 mice following RO15-4513 administration

The purpose of this study was to examine the effects of two partial benzodiazepine inverse agonists, RO15-4513 and FG-7142, alone and in combination with ethanol on locomotor activity in C57BL/6 mice. When administered alone, 1.5 g/kg ethanol did not significantly influence activity, confirming previous reports indicating this mouse strain is relatively insensitive to the excitatory properties of ethanol. RO15-4513 treatment also did not significantly influence locomotor activity when administered alone. However, coadministration of RO15-4513 (1.5–6 mg/kg) and ethanol markedly increased locomotor activity. Moreover, the unmasking of ethanol's stimulant action by RO15-4513 (6 mg/kg) was completely reversed by pretreatment with the benzodiazepine receptor antagonist RO15-1788. In contrast, FG-7142 (10–20 mg/kg) increased activity to the same extent in both saline and ethanol-injected mice. This effect was blocked by RO15-1788 pretreatment as well. Neither RO15-4513, FG-7142, nor RO15-1788 significantly influenced blood ethanol concentrations. It is suggested that RO15-4513 unmasked the stimulant effects of ethanol by virtue of its ability to antagonize the depressant properties of ethanol in C57BL/6 mice.     

Biotransformation of mexidol in inbred BALB/C and C57BL/6 mice

The pharmacokinetics and biotransformation of mexidol was studied in BALB/C and C57BL/6 mice. The blood plasma contains dealkylated metabolites, and the urine contains glucuronoconjugated derivatives of the drug. The process of glucuronoconjugation more intensively proceeds in C57BL/6 mice than in BALB/C mice.