Voltage- and Calcium-Gated Membrane Currents Tune the Plateau Potential Properties of Multiple Neuron Types

Many neurons exhibit regular firing that is limited to the duration and intensity of depolarizing stimuli. However, some neurons exhibit all-or-nothing plateau potentials that, once elicited, can lead to prolonged activity that is independent of stimulus intensity or duration. To better understand this diversity of information processing, we compared the voltage-gated and Ca2+-gated currents of three identified neurons from hermaphroditic Aplysia californica Two of these neurons, B51 and B64, generated plateau potentials and a third neuron, B8, exhibited regular firing and was incapable of generating a plateau potential. With the exception of the Ca2+-gated potassium current (I KCa), all three neuron types expressed a similar array of outward and inward currents, but with distinct voltage-dependent properties for each neuron type. Inhibiting voltage-gated Ca2+ channels with Ni+ prolonged the plateau potential, indicating I KCa is important for plateau potential termination. In contrast, inhibiting persistent Na+ (I NaP) blocked plateau potentials, empirically and in simulations. Surprisingly, the properties and level of expression of I NaP were similar in all three neurons, indicating that the presence of I NaP does not distinguish between regular-firing neurons and neurons capable of generating plateau potentials. Rather, the key distinguishing factor is the relationship between I NaP and outward currents such as the delayed outward current (I D), and I KCa We then demonstrated a technique for predicting complex physiological properties such as plateau duration, plateau amplitude, and action potential duration as a function of parameter values, by fitting a curve in parameter space and projecting the curve beyond the tested values.SIGNIFICANCE STATEMENT Plateau potentials are intrinsic properties of neurons that are important for information processing in a wide variety of nervous systems. We examined three identified neurons in Aplysia californica with different propensities to generate a plateau potential. No single conductance was found to distinguish plateau generating neurons. Instead, plateau generation depended on the ratio between persistent Na+ current (I NaP), which favored plateaus, and outward currents such as I KCa, which facilitated plateau termination. Computational models revealed a relationship between the individual currents that predicted the features of simulated plateau potentials. These results provide a more solid understanding of the conductances that mediate plateau generation

Voltage- and Calcium-Gated Membrane Currents Tune the Plateau Potential Properties of Multiple Neuron Types

Many neurons exhibit regular firing that is limited to the duration and intensity of depolarizing stimuli. However, some neurons exhibit all-or-nothing plateau potentials that, once elicited, can lead to prolonged activity that is independent of stimulus intensity or duration. To better understand this diversity of information processing, we compared the voltage-gated and Ca2+-gated currents of three identified neurons from hermaphroditic Aplysia californica. Two of these neurons, B51 and B64, generated plateau potentials and a third neuron, B8, exhibited regular firing and was incapable of generating a plateau potential. With the exception of the Ca2+-gated potassium current (IKCa), all three neuron types expressed a similar array of outward and inward currents, but with distinct voltage-dependent properties for each neuron type. Inhibiting voltage-gated Ca2+ channels with Ni+ prolonged the plateau potential, indicating IKCa is important for plateau potential termination. In contrast, inhibiting persistent Na+ (INaP) blocked plateau potentials, empirically and in simulations. Surprisingly, the properties and level of expression of INaP were similar in all three neurons, indicating that the presence of INaP does not distinguish between regular-firing neurons and neurons capable of generating plateau potentials. Rather, the key distinguishing factor is the relationship between INaP and outward currents such as the delayed outward current (ID), and IKCa. We then demonstrated a technique for predicting complex physiological properties such as plateau duration, plateau amplitude, and action potential duration as a function of parameter values, by fitting a curve in parameter space and projecting the curve beyond the tested values. SIGNIFICANCE STATEMENT Plateau potentials are intrinsic properties of neurons that are important for information processing in a wide variety of nervous systems. We examined three identified neurons in Aplysia californica with different propensities to generate a plateau potential. No single conductance was found to distinguish plateau generating neurons. Instead, plateau generation depended on the ratio between persistent Na+ current (INaP), which favored plateaus, and outward currents such as IKCa, which facilitated plateau termination. Computational models revealed a relationship between the individual currents that predicted the features of simulated plateau potentials. These results provide a more solid understanding of the conductances that mediate plateau generation

Patients achieving sustained deep remission, deep remission or sustained remission of rheumatoid arthritis are more likely than other responders to maintain remission or low disease activity after dose reduction or withdrawal of etanercept

Background Biologic disease-modifying antirheumatic drugs (bDMARDs) are important options for managing rheumatoid arthritis (RA). Once patients achieve disease control, clinicians may consider dose reduction or withdrawal of the bDMARD. Results from published studies indicate that some patients will maintain remission; however, others will flare. We analyzed data from three etanercept down-titration studies in patients with RA to determine what extent of remission provides the greatest predictability of maintaining remission following dose reduction or discontinuation. Methods Patients with moderate to severe RA from the PRESERVE, PRIZE, and Treat-to-Target (T2T) randomized controlled trials were included. We determined the proportion of patients achieving remission with etanercept at the last time point in the induction period, and sustained remission (last two time points), according to the Disease Activity Score 28-joints (DAS28), the American College of Rheumatology (ACR)/European League Against Rheumatism (EULAR) Boolean criteria, and the clinical disease activity index (CDAI). We also calculated the proportion achieving DAS28 deep remission (DAS28 ≤ 1.98), sustained deep remission (last two time points), and low disease activity (LDA), and LDA according to the CDAI. Then, we evaluated whether they maintained remission or LDA following etanercept dose reduction or withdrawal. Results Patients achieving sustained and/or deep remission were more likely than patients achieving remission or LDA to maintain remission/LDA after etanercept dose reduction or withdrawal. In PRESERVE, the proportions of patients with DAS28 sustained deep remission, deep remission, sustained remission, remission, and LDA who maintained remission following etanercept dose reduction were 81%, 67%, 58%, 56%, and 36%, respectively, P < 0.001 for trend. In PRESERVE, this trend was significant when etanercept was discontinued and when ACR/EULAR Boolean and CDAI remission criteria were used. Although some sample sizes were small, the PRIZE and T2T studies also demonstrated response trends according to ACR/EULAR Boolean and CDAI remission criteria, and T2T demonstrated response trends according to DAS28. Conclusions These results suggest that patients achieving disease control according to a stringent definition, such as sustained ACR/EULAR Boolean or CDAI remission, or a new definition of sustained deep remission by DAS28, have a higher probability of remaining in remission or LDA following etanercept dose reduction or withdrawal

Glucose metabolism and oscillatory behavior of pancreatic islets

A variety of oscillations are observed in pancreatic islets.We establish a model, incorporating two oscillatory systems of different time scales: One is the well-known bursting model in pancreatic beta-cells and the other is the glucose-insulin feedback model which considers direct and indirect feedback of secreted insulin. These two are coupled to interact with each other in the combined model, and two basic assumptions are made on the basis of biological observations: The conductance g_{K(ATP)} for the ATP-dependent potassium current is a decreasing function of the glucose concentration whereas the insulin secretion rate is given by a function of the intracellular calcium concentration. Obtained via extensive numerical simulations are complex oscillations including clusters of bursts, slow and fast calcium oscillations, and so on. We also consider how the intracellular glucose concentration depends upon the extracellular glucose concentration, and examine the inhibitory effects of insulin.Comment: 11 pages, 16 figure

Treating rheumatoid arthritis to target: the patient version of the international recommendations

To transcribe the treat-to-target (T2T) recommendations into a version that can be easily understood by patients. A core group of physicians and patients involved in the elaboration of the T2T recommendations produced a draft version of the T2T recommendations in lay language. This version was discussed, changed and reworded during a 1-day meeting with nine patients with rheumatoid arthritis (RA) from nine different European countries. Finally, the level of agreement with the translation and with the content of the recommendations was assessed by the patient participants. The project resulted in a patient version of the T2T recommendations. The level of agreement with the translation and the content was high. The group discussion revealed a number of potential barriers for the implementation of the recommendations in clinical practice, such as inequalities in arthritis healthcare provision across Europe. An accurate version of the T2T recommendations that can be easily understood by patients is available and can improve the shared decision process in the management of RA

Association between 5-HTTLPR and Borderline Personality Disorder Traits among Youth

This study provides the first genetic association examination of borderline personality disorder (BPD) traits in children and adolescents (ages 9–15) using two independent samples of youth recruited from the general community. We tested the a priori hypothesis that the serotonin transporter promoter gene (5-HTTLPR) would relate specifically to BPD traits in youth. This association was hypothesized based on prior genetic association research with BPD adults and theory positing that emotion dysregulation may be a core risk process contributing to BPD. Youth provided DNA via buccal cells. Both youth and a parent completed self-report measures assessing youth's BPD traits and depressive symptoms. Results from both Study 1 (N = 242) and an independent replication sample of Study 2 (N = 144) showed that carriers of the short allele of 5-HTTLPR exhibited the highest levels of BPD traits. This relation was observed even after controlling for the substantial co-occurrence between BPD traits and depressive symptoms. This specific association between 5-HTTLPR and BPD traits among youth supports previous genetic associations with adults diagnosed with BPD and provides preliminary support for a developmental extension of etiological risk for BPD among youth

Insights into the efficacy of golimumab plus methotrexate in patients with active rheumatoid arthritis who discontinued prior anti-tumour necrosis factor therapy: post-hoc analyses from the GO-AFTER study

OBJECTIVE: Evaluate golimumab in patients with active rheumatoid arthritis (RA) and previous tumour necrosis factor-alpha (TNF) inhibitor use. METHODS: Patients (n=461) previously receiving \u3e /=1 TNF inhibitor were randomised to subcutaneous injections of placebo, golimumab 50 mg or golimumab 100 mg q4 weeks. Primary endpoint ( \u3e /=20% improvement in American College of Rheumatology (ACR20) criteria at week 14) findings have been reported for all patients in the trial. Reported herein are further assessments of efficacy/safety among patients receiving golimumab+methotrexate (MTX). RESULTS: Among efficacy-evaluable patients who received MTX at baseline, more receiving golimumab+MTX (n=201) than placebo+MTX (n=103) achieved ACR20 (40.8% vs 14.6%), ACR50 (20.9% vs 3.9%), and ACR70 (11.4% vs 2.9%) responses at week 24. Among the 137 patients who had received only one prior TNF inhibitor (adalimumab, n=33; etanercept, n=47; and infliximab, n=57), week 24 ACR20 rates were 30.3%, 46.8% and 50.9%, respectively, and thus lowest among those who previously used adalimumab. ACR20 response rates were 44.5% (61/137), 36.2% (17/47) and 23.5% (4/17) among patients who had received one, two or three TNF inhibitors, respectively. Adverse event (AE) rates were comparable across type/number of prior anti-TNF agents, but appeared somewhat higher among patients who discontinued previous TNF inhibitor(s) due to intolerance (37/49, 75.5%) versus lack of efficacy (LOE, 113/191, 59.2%). CONCLUSIONS: Patients with active RA previously treated with \u3e /=1 TNF inhibitor had clinically relevant improvement with golimumab+MTX, which appeared somewhat enhanced among those who received only etanercept or infliximab as their prior TNF inhibitor. Golimumab+MTX safety appeared similar across patients, regardless of TNF inhibitor(s) previously used, with fewer AEs occurring among patients who discontinued prior therapy for LOE. already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions