Impaired myosin isoform shift and calcium transients contribute to cellular pathogenesis of rat cirrhotic cardiomyopathy.

BACKGROUND & AIMS: Cirrhotic cardiomyopathy is a recently recognized entity, but detailed cellular and molecular mechanisms remain unclarified. We aimed to elucidate the role of myosin heavy chain isoform shifts and their relation to calcium transients in the contractile kinetics of cirrhotic rats. METHODS: Cirrhosis was induced in male Lewis Brown-Norway rats by bile duct ligation (BDL). Myosin heavy chain (MHC) isoform distribution was evaluated by gel electrophoresis. Contractile force, Ca2+ transients and cell shortening were studied at varied frequency and extracellular [Ca2+ ]. T-tubular integrity was analysed by power spectrum analysis of images of myocytes stained with di-8-ANEPPS. RESULTS: Compared with sham controls, the phenotypes of cirrhotic rats were as follows: (a) alpha-myosin heavy chain shifted to beta-MHC isoform; (b) mild loss of T-tubular integrity in myocytes; (c) a reduced maximum and rate of rise of the Ca2+ transient (max F/Fo ); (d) a reduction in both the rate of rise and fall of contraction; (e) decreased maximal force-generating capacity; (f) loss of the inotropic effect of increased stimulus frequency; (g) unchanged sensitivity of force development to varied extracellular [Ca2+ ] and (h) increased spontaneous diastolic sarcomere length fluctuations. CONCLUSION: Cardiomyocytes and ventricular trabeculae in a cirrhotic rat model showed features of typical heart failure including systolic and diastolic prolongation, impaired force-frequency relation and decreased force-generating capacity. Impaired myosin isoform shift and calcium transients are important contributory mechanisms underlying the pathogenesis of the heart failure phenotype seen in cirrhosis.

Clonidine Does Not Reduce Pain or Opioid Consumption After Noncardiac Surgery.

BACKGROUND: Clonidine is an α2-adrenoceptor agonist, which has analgesic properties. However, the analgesic efficacy of perioperative clonidine remains unclear. We, therefore, tested the hypothesis that clonidine reduces both pain scores and cumulative opioid consumption during the initial 72 hours after noncardiac surgery. METHODS: Six hundred twenty-four patients undergoing elective noncardiac surgery under general and spinal anesthesia were included in this substudy of the PeriOperative ISchemia Evaluation-2 trial. Patients were randomly assigned to 0.2 mg oral clonidine or placebo 2 to 4 hours before surgery, followed by 0.2 mg/d transdermal clonidine patch or placebo patch, which was maintained until 72 hours after surgery. Postoperative pain scores and opioid consumption were assessed for 72 hours after surgery. RESULTS: Clonidine had no effect on opioid consumption compared with placebo, with an estimated ratio of means of 0.98 (95% confidence interval, 0.70-1.38); P = 0.92. Median (Q1, Q3) opioid consumption was 63 (30, 154) mg morphine equivalents in the clonidine group, which was similar to 60 (30, 128) mg morphine equivalents in the placebo group. Furthermore, there was no significant effect on pain scores, with an estimated difference in means of 0.12 (95% confidence interval, -0.02 to 0.26); 11-point scale; P = 0.10. Mean pain scores per patient were 3.6 ± 1.8 for clonidine patients and 3.6 ± 1.8 for placebo patients. CONCLUSIONS: Clonidine does not reduce opioid consumption or pain scores in patients recovering from noncardiac surgery.

Intraoperative core temperature patterns, transfusion requirement, and hospital duration in patients warmed with forced air.

BACKGROUND: Core temperature patterns in patients warmed with forced air remain poorly characterized. Also unknown is the extent to which transient and mild intraoperative hypothermia contributes to adverse outcomes in broad populations. METHODS: We evaluated esophageal (core) temperatures in 58,814 adults having surgery lasting >60 min who were warmed with forced air. Independent associations between hypothermic exposure and transfusion requirement and duration of hospitalization were evaluated. RESULTS: In every percentile subgroup, core temperature decreased during the first hour and subsequently increased. The mean lowest core temperature during the first hour was 35.7 ± 0.6°C. Sixty-four percent of the patients reached a core temperature threshold of <36°C 45 min after induction; 29% reached a core temperature threshold of <35.5°C. Nearly half the patients had continuous core temperatures <36°C for more than an hour, and 20% of the patients were <35.5°C for more than an hour. Twenty percent of patients had continuous core temperatures <36°C for more than 2 h, and 8% of the patients were below 35.5°C for more than 2 h. Hypothermia was independently associated with both transfusions and duration of hospitalization, although the prolongation of hospitalization was small. CONCLUSIONS: Even in actively warmed patients, hypothermia is routine during the first hour of anesthesia. Thereafter, average core temperatures progressively increase. Nonetheless, intraoperative hypothermia was common, and often prolonged. Hypothermia was associated with increased transfusion requirement, which is consistent with numerous randomized trials.

The association between perioperative hemoglobin and acute kidney injury in patients having noncardiac surgery.

BACKGROUND: Acute kidney injury (AKI) is a common complication of noncardiac surgery and is associated with excess morbidity and mortality. Perioperative hemoglobin concentrations are strongly associated with surgical mortality, but little is known about their relationship with AKI. We studied hemoglobin concentration before and 24 hours after surgery and its association with AKI. METHODS: We performed a single-center observational cohort study using clinical and administrative data from the Cleveland Clinic, Cleveland, OH. In patients with normal preoperative renal function, we examined the association between the outcome of AKI and the exposures of preoperative hemoglobin concentration and decrements in hemoglobin concentration in the first 24 hours after surgery using logistic regression and controlling for important confounding variables. RESULTS: We included 27,381 patients who had 33,330 noncardiac surgeries. AKI developed in 2478 (7.4%) surgeries. Preoperative hemoglobin concentrations were <12.0 g/dL in 9566 (29%) patients. Hemoglobin concentrations decreased by >4.0 g/dL in 10,808 (32%) patients. Compared with patients with a preoperative hemoglobin >12.0 g/dL, the adjusted odds ratio (OR) for AKI was 2.01 (95% confidence interval [CI], 1.8-2.3) for those with a preoperative hemoglobin between 10.1 and 12.0 g/dL and was 3.7 (95% CI, 2.6-5.4) for those with a preoperative hemoglobin <8.0 g/dL. Compared with patients who did not have a decrease in postoperative hemoglobin, a decrement of 1.1 to 2.0 g/dL was associated with an adjusted OR of 1.51 (95% CI, 1.15-1.98), and a decrement of >4.0 g/dL with an OR of 4.7 (95% CI, 3.6-6.2) for AKI. CONCLUSIONS: Low preoperative and early postoperative decrements in hemoglobin concentrations are strongly associated with postoperative AKI in a graded manner. Given the frequency of low perioperative hemoglobin and decreases in hemoglobin concentration, research is needed to determine whether there are safe treatment strategies to mitigate the risk of AKI.

Chemotherapy within 30 days before surgery does not augment postoperative mortality and morbidity.

BACKGROUND: Preoperative chemotherapy is frequently given to shrink or decrease the chance of metastasis. However, chemotherapy has well-recognized side effects that may complicate the perioperative period. We therefore tested the hypotheses that chemotherapy within 30 days before cancer surgery is associated with an increased risk of mortality and with a composite of major morbidities within 30 postoperative days. METHODS: We evaluated 971,455 patients from the American College of Surgeons National Surgical Quality Improvement Program database. Patients were defined as having chemotherapy when they were given any chemotherapy for malignancy within 30 days before surgery. We successfully matched 1,348 pairs of chemotherapy recipients and non-recipients. RESULTS: Twenty-one of the 1,348 (1.6%) non-chemotherapy patients died within 30 days after surgery compared with 30 of the 1,348 (2.2%) chemotherapy patients. The odds of mortality were not statistically different between groups based on our logistic regression model [odds ratio (OR) = 1.47; 95% confidence interval (CI) 0.82 to 2.64; P = 0.19]. The most common complication observed was wound infection in 13.1% of non-chemotherapy patients compared with 14.2% of the chemotherapy patients. There was similarly no difference between groups for the collapsed composite of major morbidities [OR = 1.17; 95% CI 0.97 to 1.42; P = 0.09]. CONCLUSION: Preoperative use of neoadjuvant chemotherapy in cancer patients undergoing resection surgeries was not associated with a higher rate of early postoperative complications or mortality.

Role of cardiac myofilament proteins titin and collagen in the pathogenesis of diastolic dysfunction in cirrhotic rats.

BACKGROUND & AIMS: Significance of diastolic dysfunction in cirrhotic cardiomyopathy has been brought to the forefront with several reports of unexpected heart failure following liver transplantation and transjugular intrahepatic portosystemic stent-shunt, but the etiology remains unclear. The present study investigated the role of passive tension regulators - titin and collagen - in the pathogenesis of this condition. METHODS: Cirrhosis was induced by bile duct ligation (BDL) in rats, while controls underwent bile duct inspection with no ligation. Four weeks after operation, cardiac mRNA and protein levels of titin, collagen, and protein kinase A (PKA) were determined. Diastolic function was examined in isolated right ventricular cardiomyocytes, while passive tension was examined in right ventricular trabeculae muscles. RESULTS: In BDL animals, diastolic return velocity was significantly decreased, relaxation time increased and passive tension increased. However, no significant difference in mRNA and protein levels of titin was observed. PKA mRNA and protein levels were significantly decreased in BDL animals. Collagen levels were also significantly altered in the BDL group. CONCLUSIONS: Therefore, diastolic dysfunction exists in cirrhosis with alterations in titin modulation, PKA levels, and collagen configuration contributing to the pathogenesis of this condition.

The nonadrenergic noncholinergic-mediated relaxation of corpus cavernosum was impaired in chronic lithium-treated rats: improvement with l-arginine.

One-third of lithium-treated men complain from sexual dysfunction, although the exact mechanisms of which are not yet known. In this study we investigated the effect of chronic lithium (LiCl, 600 mg/l for 30 days) administration on the neurogenic relaxation of isolated rat corpus cavernosum. The corporal strips were precontracted with phenylephrine and electrical field stimulation (EFS) was applied to obtain relaxation. Relaxation to EFS was significantly (P<0.001) impaired in LiCl-treated rats. The nitric oxide (NO) synthase inhibitor Nomega-nitro-l-arginine methyl ester (l-NAME; 100 microM) inhibited the relaxation to EFS in both LiCl-treated and control rats. The NO precursor l-arginine, at per se noneffective concentration (0.1 mM), significantly (P<0.001) enhanced the EFS-induced relaxation of LiCl-treated corporal strips. The relaxation responses to the NO donor sodium nitroprusside were similar between two groups. These data demonstrate that chronic lithium treatment could impair the NO-mediated neurogenic relaxation of rat corpus cavernosum which could be prevented by l-arginine.

Seizure susceptibility alteration following reversible cholestasis in mice: Modulation by opioids and nitric oxide.

There is an increasing body of evidence that the central nervous system is affected by cholestatic liver disorders. Cholestasis has been shown to result in a decreased seizure propensity which is believed to be mediated by an increased opioidergic tone and nitric oxide (NO) signaling pathway. In this study, we used a reversible chemically-induced cholestasis model in mice to investigate the changes in seizure susceptibility. The cholestasis was induced by intragastric administration of alpha-naphthylisothiocyanate (ANIT) (100 mg/kg) or vehicle (corn oil). The threshold to generalized clonic seizures induced by timed intravenous infusion of pentylenetetrazole (PTZ) was used as an index of seizure propensity. The role of opioid receptors and NO pathway in the changes of seizure threshold, and the responsiveness to the anticonvulsant effect of opioid agonist, morphine, during and after the resolution of cholestasis was studied in this reversible paradigm of cholestatic disease. A significant increase in cholestasis-related biochemical markers as well as in clonic seizure threshold was observed; it was maximal at day 3 after cholestasis induction and slowly decreased to normal thereafter. Seizure threshold rise was inhibited by chronic administration of the opioid antagonist naltrexone or acute administration of N-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NO production. Co-administration of subeffective doses of L-NAME and naltrexone showed an additive effect. Injection of an anticonvulsant dose of morphine on day 7 after cholestasis induction did not increase seizure threshold, suggestive of a downregulation of receptors even after cholestasis resolution. These data shows that ANIT-induced cholestasis leads to a reversible increased resistance to PTZ-induced seizures through an opioid/NO-mediated pathway, and is probably accompanied by downregulation of opioid receptors.

Effect of low-dose aspirin therapy on implantation rate in women undergoing in-vitro fertilization cycles.

OBJECTIVE: To determine the effect of low-dose aspirin on ovarian response, implantation and pregnancy rates in patients undergoing in-vitro fertilization (IVF) cycles. METHODS: We performed a randomized analysis of 145 infertile women with a mean+/-SD age of 29.6 +/- 4.47 years who underwent cycles of IVF. Patients received 100 mg of aspirin (n=72) or placebo (n=73) daily. This study was conducted in Royan Institute, Tehran, Iran from April 2002 to January 2004. Aspirin was started on the 21st of their preceding menstrual cycle and it was continued until menstruation or a negative pregnancy test. Pregnant women received the medication until 12 weeks of pregnancy. The main outcome measures were number of follicles >or=15 mm, number of oocytes retrieved, serum E2 levels, cancellation rate, Ovarian Hyperstimulation Syndrome (OHSS) occurrence, number of embryos transferred, and implantation and pregnancy rates. RESULTS: There were statistically significant differences between the treatment group and the control group in the number of follicles (7.4 +/- 4.1 versus 9.0 +/- 4.8) and OHSS occurrence (5.6% versus 23.3%) but not in the other measures. CONCLUSION: The addition of aspirin low dose (100 mg/daily) to the standard long protocol for oocyte retrieval did not improve implantation and pregnancy rates in unselected patients undergoing IVF cycles.

Therapy insight: Cirrhotic cardiomyopathy.

Liver cirrhosis is associated with several cardiovascular disturbances. These disturbances include hyperdynamic systemic circulation, manifested by an increased cardiac output and decreased peripheral vascular resistance and arterial pressure. Despite the baseline increase in cardiac output, cardiac function in patients with cirrhosis is abnormal in several respects. Patients show attenuated systolic and diastolic contractile responses to stress stimuli, electrophysiological repolarization changes, including prolonged QT interval, and enlargement or hypertrophy of cardiac chambers. This constellation of cardiac abnormalities is termed cirrhotic cardiomyopathy. It has been suggested that cirrhotic cardiomyopathy has a role in the pathogenesis of cardiac dysfunction and even overt heart failure after transjugular intrahepatic portosystemic shunt placement, major surgery and liver transplantation. Cardiac dysfunction contributes to morbidity and mortality after liver transplantation, even in many patients who have no prior history of cardiac disease. Depressed cardiac contractility contributes to the pathogenesis of hepatorenal syndrome, especially in patients with spontaneous bacterial peritonitis. Pathogenic mechanisms underlying cirrhotic cardiomyopathy include cardiomyocyte-membrane biophysical changes, attenuation of the stimulatory beta-adrenergic system and overactivity of negative inotropic systems mediated via cyclic GMP. The clinical features, general diagnostic criteria, pathogenesis and treatment of cirrhotic cardiomyopathy are discussed in this review.

Multisource feedback in professionalism for anesthesia residents.

STUDY OBJECTIVE: To assess professionalism in anesthesiology residents, it is important to obtain evaluations from people with whom they interact on daily basis. The purpose of this study was to evaluate the effect of a Multisource feedback (MSF) on resident's professional behavior and to assess the effect of faculty feedback on resident performance. DESIGN: This study was a two-group randomized clinical trial. SETTING: Residents were recruited from Cleveland Clinic Children's Hospital. PATIENTS: Participants included twenty eight residents doing a two-month rotation in Pediatric Anesthesia. INTERVENTIONS: Multisource feedback questionnaires were developed and then validated using face and content validity. Residents were randomly assigned to a feedback group or a control group. Both groups received the MSF evaluation. Only the group assigned to feedback had a 'coaching meeting' every month creating strategies for improvement. MEASUREMENTS: MSF questionnaires were validated using a face validation and expert content validity. The effect of MSF on a professionalism questionnaire was assessed using analysis of covariance and linear mixed effects regression models. MAIN RESULTS: Observed test-retest agreement was greater than 0.90 for all items, with more than half of kappa statistics greater than 0.50. Cronbach's alpha was 0.71.The MSF increased the self-assessment score with an estimated effect of 0.21 (95% CI 0.06, 0.37), P=.015. There was no detected effect on patient family evaluation, with mean difference (CI) in change from baseline of 0.03 (-0.15, 0.21), P=.77, faculty evaluation, 0.21 (-0.02, 0.44), P=.08, or coworker evaluation 0.13 (-0.11, 0.37). CONCLUSIONS: Our new multi-source feedback questionnaire to assess professionalism had good reliability and internal consistency. Using our validated questionnaire we assessed the effect of a monthly feedback to improve professionalism in anesthesia residents. While we did see improvement in anesthesiology residents' self-assessment, we did not see a similar effect on patient family, faculty or coworker evaluations.

The synergistic anticonvulsant effect of agmatine and morphine: possible role of alpha 2-adrenoceptors.

Recent demonstrations of the anticonvulsant properties of agmatine suggest it may be considered as a potential adjunct for protection against seizure. We investigated the possibility of an additive anticonvulsant effect between low doses of agmatine and morphine. The thresholds for the clonic seizures induced by the intravenous administration of gamma-aminobutyric acid (GABA)-antagonist, pentylenetetrazole (PTZ) were assessed in mice. Morphine at lower doses (1-3mg/kg) increased and at higher doses (30, 60 mg/kg) decreased the seizure threshold. Pretreatment with a per se non-effective dose of agmatine (1mg/kg) potentiated the anticonvulsant effect of morphine. The combination of subeffective doses of agmatine and morphine led to potent anticonvulsant effects. The pro-convulsant effect of morphine was attenuated by agmatine. Yohimbine with a dose (1mg/kg) incapable of affecting seizure threshold reversed the effect of agmatine on both anticonvulsant and pro-convulsant effects of morphine. These results suggest that agmatine potentiates the anticonvulsant effect of morphine and alpha 2-adrenoceptors may be involved in this effect.

Homocysteine alterations in experimental cholestasis and its subsequent cirrhosis.

Homocysteine (Hcy), an intermediate in methionine metabolism, has been proposed to be involved in hepatic fibrogenesis. Impaired liver function can alter Hcy metabolism. The aim of the present study was to determine plasma Hcy alterations in acute obstructive cholestasis and the subsequent biliary cirrhosis. Cholestasis was induced by bile duct ligation and sham-operated and unoperated rats were used as controls. The animals were studied on the days 7th, 14th, 21st and 28th after the operation. Plasma Hcy, cysteine, methionine, nitric oxide (NO) and liver S-adenosyl-methionine (SAM), S-adenosyl-homocysteine (SAH), SAM to SAH ratio and glutathione were measured. Chronic L-NAME treatment was also included in the study. Plasma Hcy concentrations were transiently elevated by the day 14th after bile duct ligation (P < 0.01) and subsequently returned to control levels. Similar relative fluctuations in plasma Hcy were observed in BDL rats after intraperitoneal methionine overload. Plasma methionine, cysteine and nitrite and nitrate were significantly increased after bile duct ligation. SAM to SAH ratio was diminished by the 1st week of cholestasis and remained significantly decreased throughout the study. These events were accompanied by a decrease in GSH to GSSG ratio in the liver. Chronic L-NAME treatment improved SAM to SAH ratio and prevented the elevation of plasma Hcy and methionine (P < 0.05) while couldn't influence the other parameters. In conclusion, this study demonstrates alterations in plasma Hcy and liver SAM and SAH contents in precirrhotic stages and in secondary biliary cirrhosis, for the first time. In addition, we observed that plasma Hcy concentrations in BDL rats follow a distinct pattern of alteration from what has been previously reported in other models of cirrhosis. NO overproduction may contribute to plasma Hcy elevation and liver SAM depletion after cholestasis.

Agmatine exerts anticonvulsant effect in mice: modulation by alpha 2-adrenoceptors and nitric oxide.

The effect of agmatine, an endogenous polyamine metabolite, on seizure susceptibility was investigated in mice. Acute intraperitoneal administration of agmatine (5, 10, 20, 40 mg/kg) had a significant and dose-dependent inhibitory effect on pentylenetetrazole (PTZ)-induced seizures. The peak of this anticonvulsant effect was 45 min after agmatine administration. We further investigated the possible involvement of the alpha(2)-adrenoceptors and L-arginine/NO pathway in this effect of agmatine. The alpha(2)-adrenoceptor antagonist, yohimbine (0.5-2 mg/kg), induced a dose-dependent blockade of the anticonvulsant effect of agmatine. The nitric oxide synthase (NOS) substrate, L-arginine (60 mg/kg), inhibited the anticonvulsant property of agmatine and this effect was significantly reversed by NOS inhibitor N(G)-nitro-L-arginine (L-NAME, 30 mg/kg), implying an NO-dependent mechanism for L-arginine effect. We further examined a possible additive effect between agmatine (1 or 5 mg/kg) and L-NAME (10 mg/kg). The combination of L-NAME (10 mg/kg) with agmatine (5 but not 1 mg/kg) induced a significantly higher level of seizure protection as compared with each drug alone. Moreover, a combination of lower doses of yohimbine (0.5 mg/kg) and L-arginine (30 mg/kg) also significantly decreased the anticonvulsant effect of agmatine. In conclusion, the present data suggest that agmatine may be of potential use in seizure treatment.

Lithium inhibits the modulatory effects of morphine on susceptibility to pentylenetetrazole-induced clonic seizure in mice: involvement of a nitric oxide pathway.

Lithium has been reported to inhibit opioid-induced properties. The present study examined the effect of acute and chronic administration of lithium chloride (LiCl) on morphine's biphasic modulation of susceptibility to pentylenetetrazole (PTZ)-induced clonic seizure in mice. We also examined the possible involvement of nitric oxide (NO) pathway in lithium effect. Both acute (0.1 and 1 mg/kg) and chronic (same doses, 21 consecutive days) administration of LiCl completely inhibited the anticonvulsant and proconvulsant effects of morphine (at doses 1 and 30 mg/kg, respectively). A very low and per se noneffective dose of LiCl (0.05 mg/kg) significantly inhibited both phases of morphine effect when administered concomitant with a noneffective low dose of naloxone (0.1 mg/kg). The NO synthase inhibitor N(G)-nitro-l-arginine methyl ester (L-NAME) at a per se noneffective dose of 0.3 mg/kg potentiated the inhibitory effects of low doses of LiCl (0.01 and 0.05 mg/kg) on both phases of morphine effect. l-arginine, a NO synthase substrate, at a per se noneffective dose of 30 mg/kg reversed the inhibitory effects of lithium (1 mg/kg). Lithium is capable of antagonizing both modulatory effects of morphine on seizure susceptibility even at relatively low doses. These inhibitory effects of lithium may also involve NO synthesis.

Time-dependent reduction of acetylcholine-induced relaxation in corpus cavernosum of cholestatic rats: role of nitric oxide and cyclooxygenase pathway.

The endothelium-dependent relaxation of corpus cavernosum smooth muscle and the roles of nitric oxide (NO) and arachidonic acid products of cyclooxygenase were investigated in non-operated, SHAM-operated, and bile duct-ligated rats. We further investigated the time-dependent alterations of corpus cavernosum relaxation in 2-, 7-, and 14-day bile duct-ligated animals. Acetylcholine produced concentration-dependent relaxation in phenylephrine-precontracted strips of corpus cavernosum. A significant reduction in the acetylcholine-induced relaxation was observed 2 days after bile duct ligation, and a greater reduction was observed on subsequent days. Incubation with 20 microM indomethacin reduced the acetylcholine-induced relaxation of the corpus cavernosum of unoperated rats while it had no effect in the corpus cavernosum of bile duct-ligated rats. Chronic treatment with Nomega-Nitro-L-Arginine Methyl Ester (L-NAME, 3 mg/kg/day, intraperitoneally) reduced the relaxation responses in the unoperated group while it had no effect in the bile duct-ligated group. These results show that acetylcholine-induced corporal relaxation is impaired in cholestatic rats, and this may be related to deficient nitric oxide production by the endothelium. The involvement of prostaglandins in this impairment seems unlikely.

Obstructive cholestasis alters intestinal transit in mice: role of opioid system.

Acute cholestasis is associated with increased activity of the endogenous opioid system. It is also known that opioid receptor agonists like morphine decrease the intestinal transit. The purpose of the present study was to investigate the effect of cholestasis on the small intestine transit and the possible involvement of opioid system in this phenomenon in mice. Cholestasis was induced by bile duct-ligation and intestinal transit was measured with charcoal meal and calculation of percent of transit through small intestine. The effect of chronic administration of naltrexone and acute pretreatment with morphine on intestinal transit was evaluated in bile duct-ligated (BDL) as well as unoperated (CTL) and sham-operated (SHAM) animals. The plasma alkaline phosphatase and alanine aminotransferase activities were also measured. A significant decrease in small intestine transit (%transit) was observed in BDL mice compared to SHAM animals, which was prominent even after 24 h of cholestasis. Chronic pretreatment with an opioid receptor antagonist, naltrexone, (10 mg/kg, i.p for 2, 4 or 6 days) completely restored the cholestasis-induced decrease in %transit to that of control animals. Although the acute administration of morphine (2 mg/kg, s.c.) 20 min before charcoal feeding caused a significant decrease in the intestinal transit of CTL and SHAM animals, it did not decrease the %transit of BDL animals on the day 5 after operation. Our findings show that acute cholestasis is associated with a prominent decrease in small intestine transit in mice and opioid receptors maybe involved in this phenomenon.

Opioid system blockade decreases collagenase activity and improves liver injury in a rat model of cholestasis.

BACKGROUND: Following bile duct ligation (BDL) endogenous opioids accumulate in plasma and play a role in the pathophysiology and manifestation of cholestasis. Evidence of centrally mediated induction of liver injury by exogenous opioid agonist administration, prompts the question of whether opioid receptor blockade by naltrexone can affect cholestasis-induced liver injury. METHODS: Cholestasis was induced by BDL and cholestatic and sham-operated rats received either naltrexone or saline for 7 consecutive days. On the 7th day, liver samples were collected for determining matrix metalloproteinase-2 (MMP-2) activity, S-adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) content and blood samples were obtained for measuring plasma nitrite/nitrate and liver enzyme activities. RESULTS: Naltrexone-treated BDL animals had a significant reduction in plasma enzyme activity and nitrite/nitrate level. Liver SAM : SAH ratio and SAM level improved by naltrexone treatment in cholestatic animals compared to saline-treated BDL ones. Naltrexone treatment in BDL rats led to a decrease in the level of liver MMP-2 activity, which had already increased during cholestasis. CONCLUSION: Opioid receptor blockade improved the degree of liver injury in cholestasis, as assessed by plasma enzyme and liver MMP-2 activities. The beneficial effect of naltrexone may be due to its ability to increase liver SAM level and restore the SAM : SAH ratio.

Intestinal inflammation alters the susceptibility to pentylenetetrazole-induced seizure in mice.

BACKGROUND: Inflammatory bowel disorders are associated with increased incidence of seizures. Alteration in the endogenous opioid system and overproduction of nitric oxide have been implicated in colitis. The possible contribution of opioid receptors and nitric oxide to increased seizure susceptibility was examined in a putative model of intestinal inflammation. METHODS: The alterations in clonic seizure threshold, induced by pentylenetetrazole, following the induction of intestinal inflammation by the administration of two consecutive daily oral doses of croton oil, was evaluated in mice. This model was used to evaluate the effects of pretreatment with opioid receptor antagonist naltrexone (10 mg/kg, once daily for 4 days or a single dose on the test day), non-specific nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (10 mg/kg, once daily), and specific inducible nitric oxide synthase inhibitor aminoguanidine (100 mg/kg, once daily) on seizure threshold in intestinal inflammation. RESULTS: A significant decrease in clonic seizure threshold was observed in mice with intestinal inflammation compared to the control group. Chronic pretreatment with naltrexone per se did not cause any significant change in seizure threshold, but it significantly restored the threshold in croton oil-treated mice to that of the control animals. However, acute naltrexone pretreatment (on the test day) could not restore the decreased seizure threshold to control level. Chronic pretreatment with neither NG-nitro-L-arginine methyl ester nor aminoguanidine altered the seizure threshold in the control animals and in mice treated with croton oil. CONCLUSIONS: Experimental croton oil-induced intestinal inflammation leads to a proconvulsant effect, which may have clinical relevance. Chronic alterations mediated by endogenous opioids may be involved in this process, though a direct opioid-receptor-mediated effect is unlikely. Nitric oxide synthesis, via constitutive or inducible pathways, is not involved in this increased susceptibility.

Sex and estrus cycle differences in the modulatory effects of morphine on seizure susceptibility in mice.

PURPOSE: To evaluate the effects of sex and estrus cycle on biphasic anticonvulsant and proconvulsant modulation of seizure threshold by morphine. METHODS: The threshold for the clonic seizures (CST) induced by acute intravenous administration of gamma-aminobutyric acid (GABA)-antagonist pentylenetetrazole (PTZ) was assessed in male and female mice. Estrus cycle was assessed by vaginal smears. The effect of removing circulating sex hormones was assessed by gonadectomy. RESULTS: At baseline, diestrus females had a higher CST compared with males and estrus females. Morphine at lower doses (0.5-3 mg/kg) had a significant anticonvulsant effect in males and estrus females compared with that in vehicle-treated controls, whereas female mice in diestrus phase showed a relative subsensitivity to this effect. Morphine at higher doses (30 and 60 mg/kg) significantly decreased CST in males and diestrus females, with less relative effect in estrus mice. In both phases, morphine exerted stronger effects in males compared with females. Ovariectomy brought the baseline CST to the male level and resulted in significant expression of both phases of morphine effect but did not abolish the sex difference in responsiveness to morphine. CONCLUSIONS: The biphasic modulation of seizure threshold is subject to both constitutive sex differences in sensitivity to morphine and hormonal fluctuations during the estrus cycle.