Cannabis use as a factor of lower corpulence in hepatitis C-infected patients: results from the ANRS CO22 Hepather cohort

Background

Patients with chronic hepatitis C virus (HCV) infection are at greater risk of developing metabolic disorders. Obesity is a major risk factor for these disorders, and therefore, managing body weight is crucial. Cannabis use, which is common in these patients, has been associated with lower corpulence in various populations. However, this relationship has not yet been studied in persons with chronic HCV infection.

Methods

Using baseline data from the French ANRS CO22 Hepather cohort, we used binary logistic and multinomial logistic regression models to test for an inverse relationship between cannabis use (former/current) and (i) central obesity (i.e., large waist circumference) and (ii) overweight and obesity (i.e., elevated body mass index (BMI)) in patients from the cohort who had chronic HCV infection. We also tested for relationships between cannabis use and both waist circumference and BMI as continuous variables, using linear regression models.

Results

Among the 6348 participants in the study population, 55% had central obesity, 13.7% had obesity according to their BMI, and 12.4% were current cannabis users. After multivariable adjustment, current cannabis use was associated with lower risk of central obesity (adjusted odds ratio, aOR [95% confidence interval, CI]: 0.45 [0.37–0.55]), BMI-based obesity (adjusted relative risk ratio (aRRR) [95% CI]: 0.27 [0.19–0.39]), and overweight (aRRR [95% CI]: 0.47 [0.38–0.59]). This was also true for former use, but to a lesser extent. Former and current cannabis use were inversely associated with waist circumference and BMI.

Conclusions

We found that former and, to a greater extent, current cannabis use were consistently associated with smaller waist circumference, lower BMI, and lower risks of overweight, obesity, and central obesity in patients with chronic HCV infection. Longitudinal studies are needed to confirm these relationships and to assess the effect of cannabis use on corpulence and liver outcomes after HCV cure.

Trial registration

ClinicalTrials.gov identifier: NCT01953458.

Clinical, environmental, and molecular factors associated to the occurrence and persistence of posttraumatic stress disorder after an earthquake

Post-traumatic stress disorder (PTSD) is a common and disabling condition with high incidence after an earthquake. The objective of the present study was to identify risk factors associated with the occurrence and persistence of PTSD. Individuals (18-65 years old) who experienced the earthquake of September 19th, 2017, attended the National Institute of Psychiatry (INPRFM) between October and November 2017 (baseline n = 68). Participants were followed 4-6 (first follow-up, n = 40) and 7-9 (second follow-up n = 41) months after the earthquake. Delay returning to normal activities, a negative emotional valence to a previous earthquake, comorbidity with depression, history of childhood maltreatment, and low expression of Glucocorticoid Receptor (GR) were associated with PTSD in the basal assessment. The earthquake-related variable associated with the persistence of PTSD at the second follow-up was that the earthquake had directly affected the participants, either because they were evicted, had damage to their homes, or suffered some injury. Comorbidity with dysthymia, history of childhood maltreatment, and higher severity of PTSD in the basal assessment were associated with persistent PTSD in the second follow-up. The lower expression of the FK506 binding protein 5 (FKBP5) in participants with persistent PTSD in the second follow-up was better explained by childhood physical abuse than with PTSD severity. These findings suggest that acute exposure to earthquake-related stressful situations is relevant for the initial risk of PTSD, while potential long-term stressful conditions are associated with its persistence. Likewise, molecular markers associated with hypothalamus-pituitary-adrenal-axis dysregulation were differentially associated with PTSD diagnosis at the different assessment times.

Severe liver fibrosis in the HCV cure era: major effects of social vulnerability, diabetes, and unhealthy behaviors

Background & Aims

After HCV cure, not all patients achieve significant liver fibrosis regression. We explored the effects of clinical and socio-behavioral factors on liver fibrosis, before and after HCV cure with direct-acting antivirals.

Methods

We analyzed data from the ongoing ANRS CO22 HEPATHER cohort, which prospectively collects clinical and socio-behavioral data on HCV-infected patients. Mixed-effects logistic regression models helped identify predictors of longitudinal measures of severe liver fibrosis, defined as a fibrosis-4 index >3.25. We also estimated the adjusted population attributable fractions (PAFs) for modifiable risk factors.

Results

Among the 9,692 study patients (accounting for 24,687 visits over 4 years of follow-up, 48.5% of which were post-HCV cure), 26% had severe fibrosis at enrolment. After multivariable adjustment, HCV-cured patients had an 87% lower risk of severe fibrosis. An inverse dose-response relationship was found for coffee consumption, with the risk of severe fibrosis diminishing by 58% per additional cup/day (adjusted odds ratio (aOR 0.42; 95% CI 0.38-0.46). Unemployment, low educational level, and diabetes were associated with a higher severe fibrosis risk (aOR 1.69; 95% CI 1.32-2.16, aOR 1.50; 95% CI 1.20-1.86, and aOR 4.27; 95% CI 3.15-5.77, respectively). Severe fibrosis risk was 3.6/4.6-fold higher in individuals with previous/current unhealthy alcohol use than in abstinent patients. All these associations remained valid after HCV cure. The risk factors accounting for the greatest severe fibrosis burden were unemployment, low education level, and diabetes (PAFs: 29%, 21%, and 17%, respectively).

Conclusions

Monitoring liver fibrosis after HCV cure is crucial for patients with low socioeconomic status, previous/current unhealthy alcohol use, and diabetes. Innovative HCV care models for the most socially vulnerable individuals and interventions for healthier lifestyles are needed to reinforce the positive effects of HCV cure on liver health.

Lay summary

After hepatitis C virus (HCV) cure, not all patients achieve significant liver fibrosis regression. Herein, we studied the effects of clinical and socio-behavioral factors on the risk of severe liver fibrosis. Coffee consumption was strongly inversely associated with severe fibrosis, while diabetes, previous and current unhealthy alcohol use were associated with a 4.3-, 3.6- and 4.6-fold higher risk of severe fibrosis, respectively. Unemployment and low educational level were also associated with a higher risk of severe fibrosis. All these associations remained valid after HCV cure. These results demonstrate the need to continue liver fibrosis monitoring in at-risk groups, and to facilitate healthier lifestyles after HCV cure as a clinical and public health priority.

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Liver fibrosis assessment is a key prognostic tool in the hepatitis C cure era.

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Significant liver fibrosis regression does not always occur after hepatitis C cure.

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Coffee intake displays protective effects on severe fibrosis even after HCV cure.

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Social vulnerability, diabetes, and unhealthy alcohol use predict severe fibrosis.

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Socio-behavioral factors are associated with severe fibrosis even after HCV cure.

Effect of prophylactic and therapeutic low molecular weight heparins on mortality in 15,704 COVID-19 patients. A systematic review and a meta-analysis

Background

Antithrombotic treatment, including low molecular weight heparin (LMWH), has been proposed as a potential therapy for Coronavirus disease 2019 (COVID-19), to counteract diffuse intravascular clotting activation. However, it is unclear whether prophylactic or therapeutic doses are similarly effective in reducing mortality.

Methods

We performed a systematic review and meta-analysis of clinical studies to evaluate the efficacy of heparin (either, LMWH or fondaparinux) compared to no anticoagulation in reducing overall mortality. A subgroup analysis comparing prophylactic or therapeutic regimen was performed. Secondary endpoints were major bleeding and length of hospital stay (LOS).

Results

12 studies were included, 2 prospective and 10 retrospective with 15,704 patients. Of these, 11,251 (71.6%) were on heparins. Ten studies reported data on all-cause mortality (figure), showing that both prophylactic and full dose reduced mortality (pooled Hazard Ratio [HR] 0.55, 95% confidence interval [CI] 0.48–0.63 and HR 0.49, 95% CI 0.41–0.59, respectively). The prophylactic dose was associated with a lower risk of major bleeding (Odds Ratio [OR] 0.60, 95% CI 0.41–0.87), while a non-significant trend towards an increased risk of bleeding for the therapeutic dose was noted (OR 1.55, 95% CI 0.98–2.43). Finally, LOS was evaluated in 3 studies; the mean difference for prophylactic heparin treatment was −2.38 (−3.14, −1.61) days.

Discussion

Heparin is effective in reducing mortality in COVID-19 patients, with therapeutic and prophylactic regimens showing a similar reduction in the mortality rate. Prophylactic dose may be considered as the first choice in all patients with COVID-19 requiring hospital admission.

Funding Acknowledgement

Type of funding sources: None.

Gray matter reduction in high-risk subjects, recently diagnosed and chronic patients with schizophrenia: A revised coordinate-based meta-analysis

Introduction

Characterizing neuroanatomical markers of different stages of schizophrenia (SZ) to assess of how the disorder develops is extremely important for the clinical practice. It still remains uncertain how abnormalities are formed as SZ progresses.

Objectives

We reviewed and analyzed 113 voxel based morphometry studies on people at risk of or with schizophrenia to assess GM alterations at different stages of the disorder and to functionally characterize these GM variations.

Methods

We performed a meta-analysis of voxel-based morphometry studies of genetic and clinical high-risk subjects (g-/c-HR), recently diagnosed (RDSZ) and chronic SZ patients (ChSZ). We quantified gray matter (GM) changes associated with these four conditions and compared them with contrast and conjunctional data. We performed the behavioral analysis and networks decomposition of alterations to obtain their functional characterization.

Results

Compared to previous investigations, results reveal a robust cortical-subcortical, left-to-right homotopic progression of GM loss. The right anterior cingulate is the only altered region in all conditions. Contrast analyses show left-lateralized insular, amygdalar and parahippocampal GM reduction in RDSZ, which appears bilateral in ChSZ. An overlap between RDSZ and ChSZ is observed in the left insula, amygdala, precentral and inferior frontal gyri. Functional decomposition shows involvement of the salience network, with an enlargement of the sensorimotor network in RDSZ and the thalamus-basal nuclei network in ChSZ.

Conclusions

These results can help the research on diagnostic and neuroimaging biomarkers of SZ staging, as well as on the identification of new therapeutics neuroanotomic targets that could be addressed with focused magnetic or non-invasive electric stimulation.

Disclosure

No significant relationships.

Hepatitis B virus and hepatitis delta virus subtypes circulating in Algeria and seroprevalence of HDV infection

BACKGROUND

Little is known about molecular characteristics of HBV strains circulating in Algeria and there are few data regarding HDV infection.

OBJECTIVES

The aim of this study is to describe the genetic diversity of HBV and HDV strains existing in Algeria and to determine the seroprevalence of HDV infection.

STUDY DESIGN

Plasma samples from 134 patients were analyzed by enzyme immunoassay method for HBV and HDV serological markers. Genotyping of HBV and HDV strains were performed using direct sequencing followed by phylogenetic analyses of the PreS1 and R0 region of the HBV and HDV genome respectively.

RESULTS

The PreS1 gene was successfully amplified in 119 patients (82 males and 37 females). Phylogenetic analysis of HBV strains revealed the presence of genotypes D (86.5%) and A2 (11.76%). The subgenotypes D are distributed as follows: HBV/D7 (43.5%), HBV/D3 (24.75%), HBV/D1 (16.8%) and HBV/D2 (14.85%). A recombinant between genotypes A, E and D was found. The seroprevalence of HDV infection among HBV carriers was less than 5.35%. Only one isolate of HDV genotype 1 was identified.

CONCLUSIONS

Our data indicate the predominance of HBV subgenotype D7 and a low prevalence of HDV infection.

The prognostic value of inflammation-based scores in advanced hepatocellular carcinoma patients prior to treatment with sorafenib

Background and Aims

The multikinase inhibitor sorafenib is the only currently approved drug for the indication of advanced hepatocellular carcinoma (HCC). It provides a limited gain in survival time but is frequently associated with adverse events. We currently lack simple prognostic factors in sorafenib-treated HCC patients. Various inflammation-based scores (IBSs) have been evaluated as predictors of tumor recurrence and survival in various malignancies (including HCC). The objective of the present study was to determine the prognostic value of IBSs for overall survival (OS) in advanced HCC patients prior to the initiation of sorafenib therapy.

Methods

Patients with Barcelona Clinic Liver Cancer stage C HCC were enrolled retrospectively between October 2007 and September 2015. To identify prognostic factors for OS, bivariate and multivariate analysis were performed using a Cox proportional hazards regression model.

Results

161 patients (87.0% males; median age: 67; median OS: 9.1 months) were enrolled. A multivariate analysis identified a body mass index <25kg/m² (hazard ratio (HR)=1.55, p<0.017), macroscopic vascular invasion (HR=1.63, p< 0.001), an AST level >38 U/L (HR=2.65, p<0.001), Child Pugh B stage (HR=2.59, p<0.001) and a systemic immune-inflammation index (SII) ≥600 × 10⁹ (HR 1.72, p=0.002) as independent risk factors for OS in advanced HCC.

Conclusion

IBSs (such as the SII) are novel, simple, low-cost prognostic indices in patients with advanced HCC. They may be of value in determining whether these patients may benefit from sorafenib therapy.

Increased Expression of Brain-Derived Neurotrophic Factor Transcripts I and VI, cAMP Response Element Binding, and Glucocorticoid Receptor in the Cortex of Patients with Temporal Lobe Epilepsy

A body of evidence supports a relevant role of brain-derived neurotrophic factor (BDNF) in temporal lobe epilepsy (TLE). Magnetic resonance data reveal that the cerebral atrophy extends to regions that are functionally and anatomically connected with the hippocampus, especially the temporal cortex. We previously reported an increased expression of BDNF messenger for the exon VI in the hippocampus of temporal lobe epilepsy patients compared to an autopsy control group. Altered levels of this particular transcript were also associated with pre-surgical use of certain psychotropic. We extended here our analysis of transcripts I, II, IV, and VI to the temporal cortex since this cerebral region holds intrinsic communication with the hippocampus and is structurally affected in patients with TLE. We also assayed the cyclic adenosine monophosphate response element-binding (CREB) and glucocorticoid receptor (GR) genes as there is experimental evidence of changes in their expression associated with BDNF and epilepsy. TLE and pre-surgical pharmacological treatment were considered as the primary clinical independent variables. Transcripts BDNF I and BDNF VI increased in the temporal cortex of patients with pharmacoresistant TLE. The expression of CREB and GR expression follow the same direction. Pre-surgical use of selective serotonin reuptake inhibitors, carbamazepine (CBZ) and valproate (VPA), was associated with the differential expression of specific BDNF transcripts and CREB and GR genes. These changes could have functional implication in the plasticity mechanisms related to temporal lobe epilepsy.

Increased expression of BDNF transcript with exon VI in hippocampi of patients with pharmaco-resistant temporal lobe epilepsy

A putative role of the brain-derived neurotrophic factor (BDNF) in epilepsy has emerged from in vitro and animal models, but few studies have analyzed human samples. We assessed the BDNF expression of transcripts with exons I (BDNFI), II (BDNFII), IV (BDNFIV) and VI (BDNFVI) and methylation levels of promoters 4 and 6 in the hippocampi of patients with pharmaco-resistant temporal lobe epilepsy (TLE) (n=24). Hippocampal sclerosis (HS) and pre-surgical pharmacological treatment were considered as clinical independent variables. A statistical significant increase for the BDNFVI (p<0.05) was observed in TLE patients compared to the autopsy control group (n=8). BDNFVI was also increased in anxiety/depression TLE (N=4) when compared to autopsies or to the remaining group of patients (p<0.05). In contrast, the use of the antiepileptic drug Topiramate (TPM) (N=3) was associated to a decrease in BDNFVI expression (p<0.05) when compared to the remaining group of patients. Methylation levels at the BDNF promoters 4 and 6 were similar between TLE and autopsies and in relation to the use of either Sertraline (SRT) or TPM. These results suggest an up-regulated expression of a specific BDNF transcript in patients with TLE, an effect that seems to be dependent on the use of specific drugs.

Aetiological factors of Budd-Chiari syndrome in Algeria

AIM: To study the clinical presentation of Budd-Chiari syndrome (BCS) and identify the aetiologies of this disease in Algeria.

METHODS: Patients with BCS, hospitalised in our unit from January 2004 until June 2010 were included and the aetiological factors were assessed. Patients presenting a BCS in the setting of advanced-stage cirrhosis or a liver transplantation were excluded from the study. The diagnosis was established when an obstruction of hepatic venous outflow (thrombosis, stenosis or compression) was demonstrated. We diagnosed myeloproliferative disease (MPD) by bone marrow biopsy and V617F JAK2 mutation. Anti-phospholipid syndrome (APLS) was detected by the presence of anticardiolipin antibodies, anti-β2 glycoprotein antibodies and Lupus anticoagulant. We also detected paroxysmal nocturnal haemoglobinuria (PNH) by flow cytometry. Celiac disease and Behçet disease were systematically investigated in our patients. Hereditary anticoagulant protein deficiencies were also assessed. We tested our patients for the G20210A mutation at Beaujon Hospital. Imaging procedures were performed to determine a local cause of BCS, such as a hydatid cyst or a liver tumour.

RESULTS: One hundred and fifteen patients were included. Mean follow up: 32.12 mo. Mean age: 34.41 years, M/F = 0.64. Chronic presentation was frequent: 63.5%. The revealing symptoms for the BCS were ascites (74.8%) and abdominal pain (42.6%). The most common site of thrombosis was the hepatic veins (72.2%). Involvement of the inferior vena cava alone was observed in 3 patients. According to the radiological investigations, BCS was primary in 94.7% of the cases (n = 109) and secondary in 5.2% (n = 6). An aetiology was identified in 77.4% of the patients (n = 89); it was multifactorial in 27% (n = 31). The predominant aetiology of BCS in our patients was a myeloproliferative disease, observed in 34.6% of cases. APLS was found in 21.7% and celiac disease in 11.4%. Other acquired conditions were: PNH (n = 4), systemic disease (n = 6) and inflammatory bowel disease (n = 5). Anticoagulant protein deficiency was diagnosed in 28% of the patients (n = 18), dominated by protein C deficiency (n = 13). Secondary BCS was caused by a compressing hydatic cyst (n = 5) and hepatocellular carcinoma (n = 1).

CONCLUSION: The main aetiologic factor of BCS in Algeria is MPD. The frequency of celiac disease justifies its consideration when BCS is diagnosed in our region.

Association of Budd-Chiari syndrome and celiac disease

BACKGROUND AND AIMS

An association between Budd-Chiari syndrome (BCS) and celiac disease (CD) is uncommon. The aims of our study were to investigate the etiology of BCS and to search for a particular HLA Ag pattern among patients.

PATIENTS AND METHODS

BCS diagnosis was based on Doppler ultrasound and CD diagnosis on duodenal biopsy, transglutaminase (TGAb) and gliadin antibodies (GAb). Patients were screened for prothrombotic disorders and seven had a PCR-SSO test for HLA genotypes. Patients were treated with anticoagulants and gluten-free diet.

RESULTS

Nine patients were included; mean age 27 years (20-42); sex ratio (F/M) 2; mean follow-up duration 31 months (6-54). All patients had endoscopic and histological features of CD. GAb/TGAb were found in 78 % (n=7). Ag HLA found were HLA DQβ1(*)02 (n=6) and DQβ1(*)03 (n=3). Prothrombotic conditions identified were latent myeloproliferative disorder (n=1), protein C deficiency (n=1), probable factor V Leiden (n=1) and oral contraceptive use (n=1). No prothrombotic state could be identified in the five other patients.

CONCLUSION

The BCS-CD association is relatively frequent in our country. Underlying prothrombotic conditions were absent in more than 50 % of cases, suggesting CD plays a role in the occurrence of thrombosis. HLA alleles found are strongly associated with CD, without any particular pattern for the BCS-CD association.

Prevalence of hepatitis B and C and risk factors for nonvaccination in inflammatory bowel disease patients in Northeast France

BACKGROUND

Data regarding the prevalence of hepatitis C (HCV) and hepatitis B (HBV) in inflammatory bowel disease (IBD) patients are conflicting.

METHODS

In all, 315 IBD (252 Crohn's disease [CD] and 63 ulcerative colitis [UC]) patients were consecutively recruited between June 2005 and May 2009.

RESULTS

The median age was 33 years (interquartile range [IQR]: 24-43) and median disease duration was 5 years (IQR: 2-11). Present and/or past HBV and HCV infection was found in 2.86% of 315 patients (CD: HBsAg 0.79%, anti-HBc 2.78%, anti-HCV 0.79%; UC: HBsAg 1.59%, anti-HBc 1.59%, anti-HCV 1.59%). Effective vaccination (anti-HBs without anti-HBc) was present in 48.9% of 315 patients. In multivariate analysis, age at diagnosis over 31 years (odds ratio [OR] 0.29; 95% confidence interval [CI] 0.15-0.58; P = 0.005), disease duration over 7 years (OR 0.43; 95% CI 0.23-0.83; P = 0.005), age at inclusion over 33 years (OR 0.44; 95% CI 0.20-0.94; P = 0.005), and CD (OR 0.29; 95% CI 0.15-0.58; P = 0.005) were associated with the lack of effective vaccination. Two HBsAg-positive patients, including 1 under curative nucleoside/nucleotide analog treatment, had received 6 and 7 infliximab infusions, and 1 HCV RNA-positive subject had been receiving corticosteroid and azathioprine therapies for 12 and 33 months, respectively. No viral reactivation occurred in these patients.

CONCLUSIONS

The prevalence of HBV and HCV infection in French IBD patients is similar to that of the general population. While the ECCO recommends an effective HBV vaccination in IBD, half of the patients were not vaccinated. The nonvaccination risk factors identified in our study may allow targeted vaccination coverage.

Inflammatory bowel disease and hepatitis B and C

The risk of viral B and C hepatitis has long been considered to be increased in patients with inflammatory bowel disease (IBD). Blood transfusion and surgery have been identified as the two main risk factors, suggesting nosocomial transmission could be involved. However, recent epidemiologic surveys have found that prevalence in IBD patients is similar to or even lower than that in the general population. Part of the explanation of these recent data may lie in the application of protective measures against viral infection (hepatitis B virus [HBV] vaccination and hepatitis C virus [HCV]-free blood transfusions). Sometimes fatal viral reactivations have been reported in patients on immunosuppressive therapy. Two periods can be distinguished: a) during therapy, a rise in viremia associated with a decrease of immune-mediated hepatic lesions; b) after cessation of therapy, an immune rebound with a destruction of virus-infected hepatocytes. For HBV, preemptive strategy consisting of an antiviral analog is efficient in chronic HBs antigen carriers. For HCV, the impact of immunosuppressive drugs on the natural history is unclear. Most studies report improved comfort although no biopsies were performed before and after immunosuppressive treatment. Physicians managing IBD patients should be aware of the need for screening and institute preventive measures against B and C hepatitis.

[Is it possible to stop nucleos(t)ide analogue based therapy in chronic hepatitis B?]

Nucleos(t)ide analogues are very efficient in the treatment of chronic hepatitis B. In the HBe antigen positive patients, the HBe seroconversion rates range from 12 to 22% after one year of treatment. When HBe seroconversion occure, it is possible to stop the treatment with analogue but only in non cirrhotic patients. If the treatment with analogue is continued for at least 6 months after confirmed HBeAg seroconversion, the HBe seroconversion is durable in 70-90% of patients. The follow up should be done during years. Stopping the treatment is more problematic in HBe antigen negative patients. A virological relapse occur in 44 to 80% of cases and a biochemical relapse occur in 30 to 70% of cases. Stopping the treatment with an analogue in this population should be considered only in a prospective study with careful monitoring and with a long term follow up.

Single-channel function of recombinant type 2 inositol 1,4, 5-trisphosphate receptor

A full-length rat type 2 inositol 1,4,5-trisphosphate (InsP(3)) receptor cDNA construct was generated and expressed in COS-1 cells. Targeting of the full-length recombinant type 2 receptor protein to the endoplasmic reticulum was confirmed by immunocytochemistry using isoform specific affinity-purified antibodies and InsP(3)R-green fluorescent protein chimeras. The receptor protein was solubilized and incorporated into proteoliposomes for functional characterization. Single-channel recordings from proteoliposomes fused into planar lipid bilayers revealed that the recombinant protein formed InsP(3)- and Ca(2+)-sensitive ion channels. The unitary conductance ( approximately 250 pS; 220/20 mM Cs(+) as charge carrier), gating, InsP(3), and Ca(2+) sensitivities were similar to those previously described for the native type 2 InsP(3)R channel. However, the maximum open probability of the recombinant channel was slightly lower than that of its native counterpart. These data show that our full-length rat type 2 InsP(3)R cDNA construct encodes a protein that forms an ion channel with functional attributes like those of the native type 2 InsP(3)R channel. The possibility of measuring the function of single recombinant type 2 InsP(3)R is a significant step toward the use of molecular tools to define the determinants of isoform-specific InsP(3)R function and regulation.

Transmembrane ion movements elicited by sodium pump inhibition in Helix aspersa neurons

1. Transmembrane ion movements upon sodium-pump inhibition were studied in identified neurons of the subesophageal ganglia of Helix aspersa. A two-microelectrode, voltage-clamp technique was used to measure transmembrane currents. Changes in intracellular Na+, K+, and Ca2+ concentrations were measured, in unclamped neurons, with Na(+)-sensitive microelectrodes, K(+)-sensitive microelectrodes, and with the fluorescent probe fura-2, respectively. 2. Inhibition of the sodium pump with ouabain (1 mM) elicited an increase in intracellular Na+ concentration, [Na+]i, at an initial rate of 0.42 +/- 0.05 mM/min (mean +/- SE; n = 27), and a membrane depolarization often followed by hyperpolarization. In cells clamped at -50 or -60 mV, ouabain produced an inward shift in membrane-holding current followed by an outward current usually having two components, transient and sustained, respectively. 3. Replacing external Na+ with either N-methyl-D-glucammonium or tetraethylammonium (TEA+) abolished both the ouabain-induced inward membrane current and the rise in [Na+]i, suggesting that Na+ was the charge carrier of the inward current. 4. Cd2+ (400 microM) reduced the rate of rise of the inward current by 60% and the estimated net Na+ flux by 47%. 5. The outward current was abolished by K(+)-channel blockers (10 mM TEA+ and 5 mM 4-aminopyridine or 10 nM apamin). Cd2+ (400 microM), a Ca(2+)-entry blocker, also abolished the outward current. 6. Inhibition of the sodium pump elicited a fall in [K+]i at an initial rate of 1.4 +/- 0.2 mM/min (n = 9 cells). 7. Upon inhibition of the sodium pump in neurons loaded with fura-2, [Ca2+]i increased from an estimated resting level of 147 +/- 37 nM to a maximum of 764 +/- 248 nM (n = 12 cells). 8. The rise in [Ca2+]i in the sustained presence of ouabain was transient, lasting 19.5 +/- 2.8 min, and could be prevented by removal of external Ca2+ before ouabain application or curtailed by removal of external Ca2+ during sustained ouabain exposure. The latter effect was not a consequence of exhaustion of caffeine-sensitive intracellular Ca2+ stores. 9. It is concluded that 1) the rise in [Ca2+]i upon Na(+)-pump inhibition requires the presence of external Ca2+, 2) the outward current observed upon pump inhibition is a Ca(2+)-activated K+ current flowing through apamin-sensitive channels, 3) the resting Na+ permeability involves a Cd(2+)-sensitive component, 4) a large fraction (approximately 30-60%) of the previously described ouabain-induced cell shrinkage may result from Ca(2+)-activated K+ efflux contributing to net solute and water loss.