Effects of Gap 26, a Connexin 43 Inhibitor, on Cirrhotic Cardiomyopathy in Rats.

Introduction Cirrhotic cardiomyopathy (CCM) is recognized by impaired cardiac responsiveness to stress, prolonged QT interval, and systolic and diastolic dysfunctions. Connexins are a family of transmembrane proteins that play a key role in cardiac physiology. Connexin 43 (Cx43) inhibition showed cardio-protective effects. Peptide drug Cx43 inhibitor, Gap 26, could inhibit gap junction 43. This study was designed to evaluate the effects of a connexin mimetic peptide, Gap 26, in the CCM model in rats. Methods The cirrhosis was induced through carbon tetrachloride (CCl4). On day 56, electrocardiography (ECG) was recorded, spleen weight was measured, and tissue and serum samples were collected. Further, Cx43 mRNA expression in heart tissue was checked. Results The chronotropic responses decreased in the CCl4/saline and increased in the CCl4/Gap. The spleen weight, QTc interval, and brain natriuretic peptide (BNP), tumor necrosis factor-alpha (TNF-α), aspartate aminotransferase (AST), alanine transaminase (ALT), and malondialdehyde (MDA) levels elevated in the CCl4/saline, and the spleen weight, QTc interval, and MDA and ALT levels were reduced by Gap 26 treatment. The level of nuclear factor (erythroid-derived 2) factor 2 (Nrf2) decreased in the CCl4/saline. The Cx43 expression was downregulated in the CCl4/saline and upregulated with the Gap 26 treatment. Conclusion Gap 26 not only alleviated the chronotropic hyporesponsiveness and the severity of liver damage and upregulated the atrial Cx43 expression, but it also had an antioxidant effect on the heart.

Evaluation of statins as a new therapy to alleviate chronotropic dysfunction in cirrhotic rats.

AIMS: Liver cirrhosis defines by regenerative nodules and fibrotic septa, causing a complication called cirrhotic cardiomyopathy (CCM) with chronotropic hypo-responsiveness. In addition to lowering cholesterol levels, statins yield antioxidant and anti-inflammatory effects. In liver diseases animal models, statins have been shown to decrease hepatic inflammation, fibrogenesis, and portal pressure (PP). Therefore, we evaluated the atorvastatin effect on the heart in cirrhotic rats. MATERIALS AND METHODS: Bile duct ligation (BDL) or sham operation performed on male Wistar rats and grouped as cirrhotic; BDL/Saline, BDL/Ator-7d(days) (Atorvastatin 15 mg/kg/day), and BDL/Ator-14d groups, or control; Sham/Saline, Sham/Ator-7d, and Sham/Ator-14d groups. Corrected QT interval (QTc interval), chronotropic responses, serum brain natriuretic peptides (BNP), heart tumor necrosis factor-α (TNF-α), nuclear factor erythroid 2-related factor 2 (Nrf2), and malondialdehyde (MDA) levels were studied along with atrial Ras homolog family member A (RhoA) and endothelial nitric oxide synthase (eNOS) gene expression. KEY FINDINGS: The chronotropic responses decreased in BDL/Saline and increased in BDL/Ator-7d group. The QTc interval, BNP, TNF-α, and MDA levels increased in BDL/Saline and decreased in BDL/Ator-14d group. The Nrf2 level did not change in BDL/Saline and increased in BDL/Ator-14d group. The liver inflammation and fibrosis increased in BDL/Saline and did not affect BDL/Ator-7d and BDL/Ator-14d groups. The RhoA expression was down-regulated in BDL/Saline, BDL/Ator-7d, and BDL/Ator-14d groups. The eNOS expression did not change in BDL/Saline and down-regulated in BDL/Ator-14d group. SIGNIFICANCE: Atorvastatin alleviates the chronotropic hypo-responsiveness and down-regulates the atrial RhoA and eNOS gene expression along with anti-inflammatory, antioxidant, and anti-stress effects in CCM.

Current Models for Predicting Drug-induced Cholestasis: The Role of Hepatobiliary Transport System.

Drug-induced cholestasis is the main type of liver disorder accompanied by high morbidity and mortality. Evidence for the role of hepatobiliary pumps in the cholestasis patho-mechanism is constantly increasing. Recognition of the interactions of chemical agents with these transporters at the initial phases of drug discovery can help develop new drug candidates with low cholestasis potential. This review delivers an outline of the role of these transport proteins in bile creation. It addresses the pathophysiological mechanism for drug-induced cholestasis. In-vitro models, including cell-based and membrane-based approaches and In-vivo models such as genetic knockout animals, are considered. The benefits and restrictions of each model are discussed in this review. Current understandings into the cellular and molecular process that control the activity of hepatobiliary pumps have directed to a better understanding of the pathophysiology of drug-induced cholestasis. A combination of in-vitro monitoring for transport interaction, in-silico predicting systems, and consideration of and metabolic and physicochemical properties must cause more effective monitoring of possible liver problems.

Evaluation of the effect of heat shock protein 70 targeted drugs on cirrhotic cardiomyopathy in biliary cirrhotic rats.

AIMS: Liver cirrhosis leads to cirrhotic cardiomyopathy (CCM) and chronotropic incompetence (CI). Heat shock protein 70 (Hsp70) regulates cellular apoptosis and autophagy in stress. Teprenone modulates the Hsp70 and protects against cellular injury. Thus, we aimed to evaluate the effect of teprenone on CI in biliary cirrhotic rats. MAIN METHODS: Liver cirrhosis was induced in male Wistar rats through bile duct ligation (BDL). The chronotropic responses and QT interval were studied through electrocardiography (ECG) in sham, cirrhotic, and cirrhotic/teprenone (100 mg/kg) pre-treated groups. Brain natriuretic peptide (BNP), tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and monocyte chemo-attractant protein-1 (MCP-1), and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels were investigated in serum. The Hsp70, B-cell lymphoma 2 (Bcl-2), and B-cell lymphoma 2-associated X protein (Bax) expressions were quantified through real-time polymerase chain reaction (Real-time PCR). KEY FINDINGS: The chronotropic responses were decreased significantly in cirrhotic and cirrhotic/teprenone groups. The QT interval and serum BNP, TNF-α, IL-6, ALT, AST, and MCP-1 levels were increased significantly in the cirrhotic and decreased significantly, except BNP, in the cirrhotic/teprenone group. The Hsp70 and Bax expressions increased significantly in cirrhotic and decreased significantly in the cirrhotic/teprenone group while the Bcl-2 decreased significantly in cirrhotic and increased significantly in the cirrhotic/teprenone group. SIGNIFICANCE: Teprenone does not relieve the CI and BNP changes in CCM while other indices are treated. Given that CCM is a multifactorial disease and needs to target other genes and proteins concurrent with Hsp70 to relieve CCM.

Effect of phosphatidylserine on cirrhosis-induced hepatic encephalopathy: Response to acute endotoxemia in cirrhotic rats.

BACKGROUND/AIMS: In cirrhosis, the levels of proinflammatory cytokines are high in the liver and blood. Endotoxin decreases level of consciousness in cirrhotic rats. Phosphatidylserine exists in the cell membrane structure and is essential for the survival of neurons. Phosphatidylserine receptor is found in phagocytic cells and also activates the signaling of membrane proteins in apoptotic process. Therefore this study was aimed to explore the hypothesis that hepatic encephalopathy is prevented by phosphatidylserine treatment and if so, whether this is associated with altered level of proinflammatory cytokines in the brain. METHODS: Cirrhosis was induced by surgical ligation of the bile duct in male Wister rats. The groups were treated with phosphatidylserine and saline for 4 weeks. Brain IL6, TNFα and the expression of phosphatidylserine receptor were assessed. Intraperitoneal injections of either saline or lipopolysaccharide (0.1 mg/kg) were administered to each group. Finally, animal behavior, blood ammonia and the expression of toll like receptor 4 were examined in the brain. RESULTS: Cirrhosis in rats was associated with altered expression of toll-like receptor4 in brain cortex and phosphatidylserine treatment increases toll-like receptor4 receptor expression. Phosphatidylserine had anti-inflammatory effect in healthy rats but no effect in cirrhotic rats. Chronic phosphatidylserine treatment decreased blood ammonia in BDL cirrhotic rats treated with lipopolysaccharide. CONCLUSION: The brain of cirrhotic rat is more susceptible to acute endotoxemia and chronic phosphatidylserine treatment decreases blood ammonia and encephalopathy in cirrhotic rats by encountering endotoxin. Phosphatidylserine may boost immune system against endotoxin.

Sumatriptan Increases Skin Flap Survival through Activation of 5-Hydroxytryptamine 1b/1d Receptors in Rats: The Mediating Role of the Nitric Oxide Pathway.

BACKGROUND: Random pattern skin flaps are applicable for reconstructing any defect in plastic surgery. However, they are difficult to apply because of necrosis. Sumatriptan, a selective 5-hydroxytryptamine 1b/1d agonist, is routinely used to offset acute migraine attacks. Recent studies have suggested that sumatriptan may induce vasodilation at lower concentrations. The authors' aim is to investigate the effect of sumatriptan on skin flap survival and the role of nitric oxide in this phenomenon. METHODS: Seventy-two male Sprague-Dawley rats were divided into eight groups. Increasing doses of sumatriptan (0.1, 0.3, and 1 mg/kg) were given intraperitoneally to three different groups after dorsal random pattern skin flaps were performed. To assess the exact role of 5-hydroxytryptamine 1b/1d receptors, GR-127935 was administered solely and with sumatriptan. N-ω-nitro-L-arginine methyl ester (L-NAME, a nonselective nitric oxide synthase inhibitor) was used to evaluate any possible involvement of nitric oxide in this study. All rats were examined 7 days later. RESULTS: The authors' results demonstrated that flap survival was increased by lower doses of sumatriptan compared to a control group for both 0.3 mg/kg (p = 0.03, mean difference = 32, SE = 8) and 0.1 mg/kg (p = 0.02, mean difference = 26, SE = 8). This protective effect was eliminated by coadministration of GR-127935 or N-ω-nitro-L-arginine methyl ester with sumatriptan. Histopathologic studies revealed a significant increase in capillary count and collagen deposition and a decreased amount of edema, inflammation, and degeneration. CONCLUSIONS: Sumatriptan in lower concentration increases skin flap survival by means of activation of 5-hydroxytryptamine 1b/1d receptors. This effect is mediated through the nitric oxide synthase pathway.

Thalidomide attenuates the hyporesponsiveness of isolated atria to chronotropic stimulation in BDL rats: The involvement of TNF-α, IL-6 inhibition, and SOCS1 activation.

OBJECTIVES: Cirrhotic cardiomyopathy is a complication of uncured cirrhosis which is associated with hyporesponsiveness of the heart to sympathetic stimulation. The enhancement of portal pressure, nitric oxide (NO) level, pro-inflammatory mediators and down-regulation of Suppressor of Cytokine Signaling 1 (SOCS1) are involved in this situations. The present study seeks to examine the beneficial effect of thalidomide on cirrhotic cardiomyopathy. MATERIALS AND METHODS: The male rats were grouped as: Sham/saline, Sham/Thalidomide, Bile Duct Ligation (BDL)/saline and BDL/Thalidomide. BDL model of cirrhosis was used. In the treatment groups, thalidomide (200 mg/kg/day) was administrated by intragastrial gavage for 28 consecutive days, the chronotropic response was assessed in isolated atria by isoproterenol stimulation. Serum levels of NO, IL-6 and TNF-α hepatic level were evaluated. The intrasplenic pulp pressure (ISPP) as the portal pressure and histopathologic assessment were assessed. Real time RT-PCR was used for the evaluation of SOCS1 gene expression. RESULTS: Our results showed that thalidomide administration could significantly increase the atrial chronotropic response in BDL animals. The increased level of portal pressure decreased by thalidomide in BDL animals. Thalidomide could ameliorate the histopathological conditions of BDL rats. Furthermore, the chronic treatment by this drug diminished the elevated levels of NO, TNF-α and IL-6 in BDL animals. On the other hand, hepatic SOCS1 expression was up-regulated by thalidomide treatment in this group. CONCLUSION: Thalidomide improves the chronotropic hyporesponsiveness of isolated atria in BDL. This effect is probably mediated by the inhibiting NO, TNF-α and IL-6 production, reducing portal pressure and increasing the expression of SOCS1.

Cardiac chronotropic hypo-responsiveness and atrial fibrosis in rats chronically treated with lithium.

Lithium is a widely used mood-stabilizing agent; however, it causes a variety of cardiovascular side effects including sinus node dysfunction. In this study we explored the potential adverse effects of lithium on cardiac chronotropic responsiveness, atrial tissue histology and gene expression in rats that were chronically treated with therapeutic doses of lithium. Male Wistar albino rats were given lithium chloride (2.5 g/kg) orally for 2 or 3 months. Following treatment, the atria were isolated and spontaneously beating rate and chronotropic responsiveness to ß-adrenergic stimulation was evaluated in an organ bath. Development of cardiac fibrosis was examined by histological methods. The expression of atrial Col1a1 (collagen I, alpha 1) and ß-arrestin2 was also assessed using quantitative RT-PCR. Treatment with lithium induced a significant hypo-responsiveness to adrenergic stimulation (P < 0.001) and caused fibrosis in the atrial tissue of treated rats. In addition, the expression of atrial Col1a1 mRNA was significantly increased in atrial tissues of lithium-treated animals, while ß-arrestin2 mRNA expression did not show a significant difference compared with control animals. Altogether, these findings indicate that cardiac chronotropic hypo responsiveness and associated cardiac fibrosis are side effects of chronic lithium treatment. Moreover, it seems that lithium treatment does not influence ß-arrestin2 mRNA expression.

Evaluation of Isolated Vascular Response to 5HT1A, 5HT1B1D & 5HT2A Receptors Agonist & Antagonist in Chronic Endotoxemic Rats.

The main vascular feature in endotoxemia is impaired contractile responses to vasoactive agents. We study the aortic response to 5HT11 A, 5HT1B1D and 5HT2A receptors agonist and antagonist in chronic endotoxemic rats. Intraperitoneal injection of 1 mg/kg lipopolysaccharide for 5 days induced chronic endotoxemia. Control rats received intraperitoneal injection of 1 ml/kg saline for 5 days. Rats divided into 3 groups. In first, DOI2 hydrochloride used as an agonist and sarpogrelate hydrochloride as an antagonist of 5HT2A receptor. In second, (R)-(+)-8-OH-DPAT3 and WAY1001354 used as an agonist and antagonist of 5HT1A receptor respectively. In third, Zolmitriptan used as an agonist and GR127935 hydrochloride as an antagonist of 5HT1B1D receptor. Aorta Isolated for organ bath study. Real time-PCR5 and histopathological study examined receptors gene expression and protein localization. Cumulative 8-OH-DPAT caused relaxation in control aorta (EC506 7.79±21.35 and 8.53±10.74 with and without antagonist), which was enhanced in endotoxemia (EC50 6.35±8.48 and very wide±17.38 with and without antagonist). Cumulative zolmitriptan caused relaxation in control aorta (EC50 very wide±8.65 and 8.38±8.44 with and without antagonist), which was enhanced in endotoxemia (EC50 very wide±9.53 and 8.37±13.49 with and without antagonist). DOI hydrochloride contracted the control aorta (EC50 6.51±7.14 and 5.98±1.65 with and without antagonist), which was converted to relaxation in endotoxemic group (EC50 infinity±80.43 and 7.37±20.28 with and without antagonist). PCR studies revealed enhanced 5HT1A receptor and diminished 5HT1B1D and 5HT2A receptor genes expression, while histopathological studies showed inflamed, damaged endothelium in endotoxemic aorta. Our data supports enhanced vasodilation and impaired vasoconstriction during endotoxemia.

Protective effects of magnesium sulfate against doxorubicin induced cardiotoxicity in rats.

AIMS: Clinical use of doxorubicin, an effective chemotherapeutic agent, has limited uses due to dose-dependent cardiac toxicity. It has been supposed that the production of free radicals and calcium ions overload can lead to cardiac toxicity. Magnesium is a cardioprotective drug which inhibits lipid peroxidation and reducing myocardial apoptosis. This study was aimed to explore the hypothesis that the cardiac toxicity induced by administration of doxorubicin is prevented or reduced by magnesium sulfate treatment and if so, whether this is associated with altered oxidative stress response in heart. MATERIAL AND METHODS: Male Wistar rats were intraperitoneally injected with doxorubicin and magnesium sulfate and normal saline four times per week for 2 consecutive weeks. Then electrocardiographic, inotropic and biochemical tests were performed. KEY FINDINGS: Co-administration of magnesium sulfate with doxorubicin significantly reversed alterations in the stimulation threshold and contractile force induced by doxorubicin. In addition, magnesium sulfate improved body weight loss and alleviated the mortality rate of animals induced by doxorubicin. Moreover, it was observed that lesions induced by doxorubicin decreased in animals treated with magnesium sulfate. Magnesium sulfate significantly increased Glutathione (GSH) in doxorubicin treated animals. SIGNIFICANCE: In conclusion, the results of the present study demonstrated that magnesium sulfate attenuate the cardio toxic effects of doxorubicin by increasing the activities of the antioxidants enzyme.

Evaluation of Chronic Losartan Treatment Effect on Cardiac Chronotropic Dysfunction in Biliary Cirrhotic Rats.

Cirrhosis is associated with cardiac chronotropic and inotropic dysfunction which is known as cirrhotic cardiomyopathy. Cardiac responsiveness to adrenergic stimulation is impaired in cirrhosis. Moreover, there is vagal nerve dysfunction which is related to neuromodulatory dysfunction of the angiotensin II in the cirrhosis. This study was aimed to explore the hypothesis that administration of Losartan-angiotensin II receptor antagonist increases cardiac chronotropic response to isoproterenol in cirrhotic rats; and if so, whether this is associated with altered cardiac TGF-ß receptor expression. Cirrhosis was induced by surgical ligation of the bile duct (BDL) in male Wister rats. Half of the BDL-group and control group were treated with losartan for four weeks. Four weeks after bile duct ligation or sham surgery the atria were isolated and spontaneously beating rate and chronotropic responsiveness to ß-adrenergic stimulation was assessed using standard organ bath. The pathological assessment was done on the atria. Moreover, the expression of TGF-ß has assessed the atria using quantitative RT-PCR. Bile duct ligation could induce a significant hypo-responsiveness to adrenergic stimulation. In cirrhotic rats, the chronotropic responses increased after chronic treatment with losartan, but it was not significant. The pathological study showed that losartan could not decrease fibrosis in atria in losartan treated cirrhotic group. TGF-ß expression is markedly increased in cirrhotic rats which are significantly decreased in atria following administration of losartan. These results might be considered as angiotensin II role in cirrhotic cardiomyopathy, but further studies are required to elaborate the mechanism as well as the possible advantage of losartan. We conclude that cirrhosis in rats is associated with altered expression of TGF-ß in the atrium which losartan can ameliorate it.

Pharmacological evidence for the involvement of the NMDA receptor and nitric oxide pathway in the antidepressant-like effect of lamotrigine in the mouse forced swimming test.

Lamotrigine is an anticonvulsant agent that shows clinical antidepressant properties. The aim of the present study was to investigate the involvement of N-methyl-d-aspartate (NMDA) receptors and nitric oxide-cyclic guanosine monophosphate (NO-cGMP) synthesis in possible antidepressant-like effect of lamotrigine in forced swimming test (FST) in mice. Intraperitoneal administration of lamotrigine (10mg/kg) decreased the immobility time in the FST (P<0.01) without any effect on locomotor activity in the open-field test (OFT), while higher dose of lamotrigine (30mg/kg) reduced the immobility time in the FST (P<0.001) as well as the number of crossings in the OFT. Pretreatment of animals with NMDA (75mg/kg), l-arginine (750mg/kg, a substrate for nitric oxide synthase [NOS]) or sildenafil (5mg/kg, a phosphodiesterase [PDE] 5 inhibitor) reversed the antidepressant-like effect of lamotrigine (10mg/kg) in the FST. Injection of l-nitroarginine methyl ester (l-NAME, 10mg/kg, a non-specific NOS inhibitor), 7-nitroindazole (30mg/kg, a neuronal NOS inhibitor), methylene blue (20mg/kg, an inhibitor of both NOS and soluble guanylate cyclase [sGC]), or MK-801 (0.05mg/kg), ketamine (1mg/kg), and magnesium sulfate (10mg/kg) as NMDA receptor antagonists in combination with a sub-effective dose of lamotrigine (5mg/kg) diminished the immobility time of animals in the FST compared with either drug alone. None of the drugs produced significant effects on the locomotor activity in the OFT. Based on our findings, it is suggested that the antidepressant-like effect of lamotrigine might mediated through inhibition of either NMDA receptors or NO-cGMP synthesis.

Involvement of Inflammatory Cytokines in Antiarrhythmic Effects of Clofibrate in Ouabain-Induced Arrhythmia in Isolated Rat Atria.

Considering the cardioprotective and anti-inflammatory properties of clofibrate, the aim of the present experiment was to investigate the involvement of local and systemic inflammatory cytokines in possible antiarrhythmic effects of clofibrate in ouabain-induced arrhythmia in rats. Rats were orally treated with clofibrate (300 mg/kg), and ouabain (0.56 mg/kg) was administered to animals intraperitoneally. After induction of anesthesia, the atria were isolated and the onset of arrhythmia and asystole was recorded. The levels of inflammatory cytokines in atria were also measured. Clofibrate significantly postponed the onset of arrhythmia and asystole when compared to control group (P ≤ 0.05 and P ≤ 0.01, resp.). While ouabain significantly increased the atrial beating rate in control group (P ≤ 0.05), same treatment did not show similar effect in clofibrate-treated group (P > 0.05). Injection of ouabain significantly increased the atrial and systemic levels of all studied inflammatory cytokines (P ≤ 0.05). Pretreatment with clofibrate could attenuate the ouabain-induced elevation of IL-6 and TNF-α in atria (P ≤ 0.01 and P ≤ 0.05, resp.), as well as ouabain-induced increase in IL-6 in plasma (P ≤ 0.05). Based on our findings, clofibrate may possess antiarrhythmic properties through mitigating the local and systemic inflammatory factors including IL-6 and TNF-α.

Involvement of NMDA receptors and L-arginine/nitric oxide/cyclic guanosine monophosphate pathway in the antidepressant-like effects of topiramate in mice forced swimming test.

Topiramate (TPM) is an agent primarily used in the treatment of epilepsy. Using mice model of forced swimming test (FST) the current study was basically aimed to investigate the influence of TPM on depression by inhibiting NMDA receptor and nitric oxide-cGMP production. When TPM was administered in a dose of 20 and 30 mg/kg by i.p. route it reduced the immobility time during FST. However this effect of TPM (30 mg/kg, i.p.) in the FST was abolished when the mice were pretreated either with NMDA (75 mg/kg, i.p.), or l-arginine (750 mg/kg, i.p. NO precursor), or sildenafil (5mg/kg, i.p. Phosphodiesterase 5 inhibitor). The immobility time in the FST was reduced after administration of L-NAME (10mg/kg, i.p, a non-specific NOS inhibitor), 7-nitoinidazol (30 mg/kg, i.p. a nNOS inhibitor) or MK-801 (0.05 mg/kg, i.p, a NMDA receptor antagonist) in combination with a subeffective dose of TPM (10mg/kg, i.p.) as compared with single use of either drug. Co-administrated of lower doses of MK-801 (0.01 mg/kg) or L-NAME (1mg/kg) failed to effect immobility time. However, simultaneous administration of these two agents in the same doses with subeffective dose of TPM (10mg/kg, i.p.), reduced the immobility time during FST. None of these drugs were found to have a profound effect on the locomotor activity per se during the open field test. Taken together, our data demonstrates that TPM exhibit antidepressant-like effect which is accomplished either due to inhibition of NMDA receptors or NO-cGMP production.

Cirrhosis-induced morphological changes in the retina: possible role of endogenous opioid.

AIM: To investigate the impact of cirrhosis on retinal morphology and to evaluate the role of endogenous opioids as a mediator in cirrhosis induced retinal change. METHODS: Thirty-six male rats were divided into 3 main groups; the common bile duct ligated (BDL) group, the sham-operated (Sham) group and the unoperated (Unop) group. Then each of these three main groups was divided into two subgroups; the first subgroup received daily injection of naltrexone hydrochloride (NTX) and the second group was injected with normal saline (Saline) daily. After 28d, rats were anesthetized and their right eyes were enucleated and assessed for histological changes. The thickness of the rod and cons layer, outer nuclear layer, outer plexiform layer, inner nuclear layer, inner plexiform layer and ganglion cell layer for each eye were measured in micrometers by light microscope. RESULTS: Ganglion cell layer showed significant increase in thickness in the BDL group (P<0.05). This increase was eliminated in the group where BDL rats received daily intraperitoneal injection of naltrexone hydrochloride (20 mg/kg). No other histological changes were detected in the other 5 layers we measured. CONCLUSION: The morphological change we detected in the retina of cirrhotic rats is probably due to opioids increased tone in cirrhosis since the increase in thickness in the ganglion cell layer was almost eliminated when naltrexone hydrochloride was injected. These results suggest a possible role for endogenous opioids in the morphological retinal changes detected in cirrhotic rats.

Mesenteric artery responsiveness to acetylcholine and phenylephrine in cirrhotic rats challenged with endotoxin: the role of TLR4.

Cirrhosis is associated with vascular dysfunction and endotoxemia. These experiments were designed to investigate the hypothesis that the administration of a low-dose of lipopolysaccharide (LPS) worsens vascular dysfunction in rats subjected to bile-duct ligation (BDL), and to determine whether LPS initiates changes in vascular Toll-like receptor 4 (TLR4) expression. Four weeks after BDL, the animals were given an intraperitoneal injection of either saline or LPS (1.0 mg/kg body mass). Three hours later, the superior mesenteric artery was isolated, perfused, and then subjected to the vasoconstriction and vasodilatation effects of phenylephrine and acetylcholine, respectively. Our results show that phenylephrine-induced vasoconstriction decreased in the cirrhotic vascular bed (BDL rats) compared with the vascular bed of the sham-operated animals, and that the LPS injections in the cirrhotic (BDL) rats worsened this response. LPS injection administered to the sham-operated animals had no such effect. On the other hand, both the BDL procedure and the LPS injection increased acetylcholine-induced vasorelaxation, but LPS administration to the BDL rats had no effect on this response. The mRNA levels of TLR4 did not change, but immunohistochemical studies showed that TLR4 localization switched from the endothelium to vascular smooth muscle cells following chronic BDL. In conclusion, acute endotoxemia in cirrhotic rats is associated with hyporesponsiveness to phenylephrine and tolerance to the effects of acetylcholine. Altered localization of TLR4 may be responsible for these effects.

Prostaglandin F2α modulates atrial chronotropic hyporesponsiveness to cholinergic stimulation in endotoxemic rats.

Endotoxemia induces various physiological adaptive responses such as tachycardia. There is evidence to show that inflammatory tachycardia might be linked to a direct action of prostanoids on the cardiac pacemaker cells. Recent reports have indicated that systemic inflammation may uncouple of cardiac pacemaker from cholinergic neural control in experimental animals; however, the exact mechanism of this phenomenon is uncertain. This study was aimed to explore the hypothesis that prostanoids modulate atrial chronotropic hyporesponsiveness to cholinergic stimulation in endotoxemic rats. Male albino rats were given intraperitoneal injection of either saline or lipopolysaccharide (LPS, 1 mg/kg). 3 h after saline or LPS injection, the atria were isolated and chronotropic responsiveness to cholinergic stimulation was evaluated in an organ bath. The expression of atrial cyclooxygenases (COX)-1, COX-2 and COX-3 mRNA was assessed by quantitative real-time RT-PCR and cytosocalcium-dependent phospholipase A2 (cPLA2) activity was measured in the atria. The expression of atrial COX-2 mRNA and cPLA2 activity increased significantly in endotoxemic atria (P<0.05). Incubation with prostaglandin F2α (PGF2α, 100 pM) could significantly decrease chronotropic response to cholinergic stimulation in vitro. Likewise, LPS injection could induce a significant hyporesponsiveness to cholinergic stimulation, and incubation of isolated atria with either indomethacin (5 µM) or AL-8810 (a PGF2α antagonist, 10 µM) could reverse it (P<0.01, P<0.05, respectively), while SQ29548 (a thromboxane A2 antagonist, 10 nM) was failed (P>0.05). Our data showed that PGF2α may contribute to the atrial chronotropic hyporesponsiveness to cholinergic stimulation in endotoxemic rats.

Effects of D-penicillamine on pentylenetetrazole-induced seizures in mice: involvement of nitric oxide/NMDA pathways.

Besides the clinical applications of penicillamine, some reports show that use of D-penicillamine (D-pen) has been associated with adverse effects such as seizures. So, the purpose of this study was to evaluate the effects of D-pen on pentylenetetrazole (PTZ)-induced seizures in male NMRI mice. It also examined whether N-methyl-D-aspartate (NMDA) receptor/nitrergic system blockage was able to alter the probable effects of D-pen. Different doses of D-pen (0.1, 0.5, 1, 10, 100, 150, and 250 mg/kg) were administered intraperitoneally (i.p.) 90 min prior to induction of seizures. D-Penicillamine at a low dose (0.5 mg/kg, i.p.) had anticonvulsant effects, whereas at a high dose (250 mg/kg, i.p.), it was proconvulsant. Both anti- and proconvulsant effects of D-pen were blocked by a single dose of a nonspecific inhibitor of nitric oxide synthase (NOS), L-NAME (10 mg/kg, i.p.), and a single dose of a specific inhibitor of neuronal nitric oxide synthase (nNOS), 7-nitroindazole (30 mg/kg, i.p.). A selective inhibitor of iNOS, aminoguanidine (100 mg/kg, i.p.), had no effect on these activities. An NMDA receptor antagonist, MK-801 (0.05 mg/kg, i.p.), alters the anti- and proconvulsant effects of D-pen. The results of the present study showed that the nitric oxide system and NMDA receptors may contribute to the biphasic effects of D-pen, which remain to be clarified further.

Teratogenic effects of coadministration of fluoxetine and olanzapine on rat fetuses.

Objective. Depression during pregnancy is a relatively common problem. Since little is known about the teratogenic effects of concomitant administration of fluoxetine and olanzapine during the organogenesis period, the aim of the present study was to evaluate the teratogenic effects of coadministration of fluoxetine and olanzapine on rat fetuses. Method. Forty-two pregnant rats were divided into seven groups, randomly. The first group received 0.5 mL of normal saline as the control. The second and third groups received fluoxetine at doses of 9 mg/kg and 18 mg/kg, respectively. Olanzapine was injected at 3 mg/kg and 6 mg/kg to the fourth and fifth groups, respectively. The sixth group received 9 mg/kg fluoxetine and 3 mg/kg olanzapine. Finally, the seventh group was administrated with fluoxetine and olanzapine at 18 mg/kg and 6 mg/kg, respectively. Drugs were injected intraperitoneally between day eight and day 15 of the pregnancy. On the 17th day of pregnancy, the fetuses were removed and micro-/macroscopically studied. Results. Fetuses of rats receiving high doses of these drugs showed a significant rate of cleft palate development, premature eyelid opening and torsion anomalies, compared to the control group (P ≤ 0.01). It is concluded that these drugs can lead to teratogenicity, so their concomitant use during pregnancy should be avoided, or if necessary their doses must be decreased.

Effect of endotoxin on heart rate dynamics in rats with cirrhosis.

Reduced heart rate variability (HRV) is a hallmark of systemic inflammation which carries negative prognostic information in sepsis. Decreased HRV is associated with partial uncoupling of cardiac pacemaker from cholinergic neural control during systemic inflammation. Sepsis is a common complication in liver cirrhosis with high mortality. The present study was aimed to explore the hypothesis that endotoxin uncouples cardiac pacemaker from autonomic neural control and reduces HRV in an experimental model of cirrhosis. Cirrhosis was induced by surgical ligation of the bile duct in rats. Cirrhotic rats were given intraperitoneal injection of either saline or lipopolysaccharide (endotoxin, 1mg/kg). Changes in HRV indices were studied in conscious rats using implanted telemetric probes. The atria were isolated and chronotropic responsiveness to cholinergic stimulation was assessed in vitro. Endotoxin injection induced a significant tachycardia and decreased short-term and long-term HRV indices in control rats. However, endotoxin was unable to increase heart rate in cirrhotic animals. In contrast with control rats, endotoxin induced biphasic changes in short-term HRV in cirrhotic rats. Acute endotoxin challenge reduced long-term HRV with 60-min delay in comparison with control animals. Endotoxin injection was associated with a significant hypo-responsiveness to cholinergic stimulation in control rats in vitro. Endotoxin did not change atrial chronotropic responsiveness to cholinergic stimulation in cirrhotic rats. Our data shows that cirrhosis is associated with development of tolerance to cardiac chronotropic effect of endotoxin in rats.