Action Potential Measurements Research Articles

Insertion trauma of a novel inner ear catheter for intracochlear drug delivery.

Even with recent research advances, effective delivery of a compound to its target cells inside the inner ear remains a challenging endeavor due to anatomical and physiological barriers. Direct intracochlear drug administration with an inner ear catheter (IEC) aims to overcome this obstacle and strives to provide a safe and efficient way for inner ear pharmacotherapy. The goal of this study was to histologically and audiologically evaluate the traumatic properties of a novel IEC for intracochlear drug delivery in a large animal model. Seven inner ears of piglets that had undergone intracochlear fluorescein isothiocyanate dextran application via an IEC (n = 4) or round window membrane (RWM) puncture with a needle (n = 3) followed by sequential apical perilymph sampling were histologically analyzed. Additionally, obtained objective auditory compound action potential and cochlear microphonic measurements were compared. Cochlear cryosections were stained using hematoxylin and eosin, and preservation of inner ear structures was investigated. Moreover, one cochlea was methylmethacrylate-embedded and analyzed with the IEC in situ. Histological evaluation revealed an atraumatic insertion and subsequent compound application in a majority of IEC-inserted inner ears. Click cochlear compound action potential (CAP) shifts in the IEC groups reached a maximum of 5 dB (1.25 ± 2.5 dB) post administration and prior to perilymph sampling. In comparison, application by RWM puncture generated a maximum click CAP hearing threshold shift of 50 dB (23.3 ± 23.1 dB) coinciding with coagulated blood in the basal cochlear turn in one specimen of the latter group. Furthermore, in situ histology showed an atraumatic insertion of the IEC demonstrating preserved intracochlear structures. The IEC appears to be a promising and efficient way for inner ear drug delivery. The similarities between the porcine and human inner ear enhance the clinical translation of our findings and increase confidence regarding the safe applicability of the IEC in human subjects.

Right ventricular outflow tract cardiomyocytes possess distinct calcium handling and contractile properties

Abstract Funding Acknowledgements Type of funding sources: Other. Main funding source(s): Rembrandt Research Grant 2021 Background The right ventricular outflow tract (RVOT) is the predominant site of origin of idiopathic ventricular tachycardia. Idiopathic ventricular tachycardias are typically sensitive to adenosine, consistent with triggered activity caused by delayed afterdepolarizations due to intracellular Ca2+ overload. The distinct properties of RVOT myocytes explaining increased susceptibility to Ca2+ overload and triggered activity are unknown. Purpose To identify distinct RVOT electrophysiological properties including Ca2+ handling and its molecular underpinnings. Methods and Results Experiments were performed using freshly isolated cardiomyocytes from the RVOT and right ventricular (RV) apex of adult rabbit hearts. To identify distinct RVOT electrophysiological properties, we employed the perforated patch clamp methodology and measured action potentials and L-type Ca2+ current. Action potentials of RVOT myocytes were significantly shorter compared to RV myocytes, particularly at lower pacing frequency. L-type Ca2+ current peak density was significantly lower in RVOT myocytes compared to RV myocytes (34.0 ± 9.1% at 0 mV). However, voltage-dependencies of L-type Ca2+ current activation and inactivation were not statistically different. Next we measured intracellular Ca2+ transients using the fluorescent Ca2+ indicator indo-1 and found that Ca2+ transient amplitudes were significantly lower in RVOT myocytes compared to RV myocytes. To investigate a relationship between RVOT myocyte Ca2+ handling and contractility, we performed unloaded sarcomere shortening measurements using the Cytocypher Multicell system. Shortening of relaxation time following increased pacing frequency (1-2 Hz) was significantly larger for RVOT myocytes compared to RV myocytes. To identify molecular factors explaining the distinct properties of RVOT myocytes, we performed RNA-seq analysis of differential gene expression using the DESeq2 method. RVOT and RV transcriptomic profiles consisted of 30 differentially expressed genes (adjusted p ≤ 0.05). One of genes significantly higher expressed by the RV was synaptotagmin (SYT1), a Ca2+ sensor and positive regulator of the cardiac L-type Ca2+ channel through inhibition of syntaxin 1A [Ref. 1, 2]. Conclusion RVOT cardiomyocytes possess distinct electrophysiological and contractile properties, reflected by shorter action potentials, lower Ca2+ transient amplitudes, and larger shortening of relaxation time upon increasing pacing frequency. The RVOT and RV have similar but distinct gene expression signatures. Future experiments will focus on determining the role of SYT1 and other genes in regulation of the L-type Ca2+ current and Ca2+ handling in RVOT myocytes.Distinct properties of RVOT myocytes.Transcriptomic profile of the RVOT.

Pectus carinatum, small pneumothorax, and Brugada patterns: First description and pathophysiological analysis

Pectus carinatum is a chest wall deformity where the breastbone and ribs protrude outward, sometimes referred to as “pigeon chest” due to the bird-like appearance of the chest. This condition occurs in approximately 1 in 1000 children, more commonly affecting boys than girls. Pectus carinatum tends to worsen as a child grows, especially during puberty, with about 15% of the children experiencing associated conditions like scoliosis. We present a case report of a young patient with pectus carinatum who experienced a small right apex pneumothorax and exhibited Brugada patterns on electrocardiogram tracing. This is the first clinical case reporting Brugada pattern presentation in both a patient with pectus carinatum and a small pneumothorax. We have conducted a clinical anatomical and electrocardiographic analysis to explore a physiopathological explanation for these findings, considering that our patient has no history or clinical signs of Brugada Syndrome. To further elucidate the clinical, anatomical, and electrocardiographic findings observed in our patient, detailed analyses were conducted. These investigations focused on how the pectus carinatum may influence electrocardiographic patterns through structural alterations of the thoracic wall, potentially modifying the transmural electrical field across the myocardium. This analysis aimed to explore a physiopathological explanation for the Brugada patterns observed, considering our patient’s unique thoracic anatomy and the absence of clinical Brugada Syndrome. We conclude that: 1. Pectus carinatum may create a window that facilitates the less resistive measurement of cardiac action potentials; 2. Small pneumothoraces can induce modifications in the cardiac electrical signal detected by surface electrodes, and pectus carinatum could unmask these modifications; and 3. Surface electrodes may measure subepicardial potentials that include and are modified by adjacent pericardial tissues, potentially resulting in alterations in transmural potential differences, thus producing fictitious Brugada patterns. Similarly, there is a possibility that the right ventricular outflow tract may be included within the subendocardial potentials.

Association Between Intracochlear Electrode Design and Electrically-Evoked Compound Action Potential Measures in Cochlear Implant Users.

Cochlear implant (CI) electrode design has changed over time. Changes in intracochlear electrode design might influence the spread of neural activation along the auditory nerve and the number of independent channels. This study aimed to investigate the impact of intracochlear electrode design on the electrode-neuron interface using electrophysiological measures. Prospective cohort study. A single tertiary hospital. Fifty-two ears who were implanted with CI divided into 3 groups based on the design of intracochlear electrode arrays. Twenty-three ears were implanted with lateral wall straight electrodes. Eighteen ears were implanted with the slim perimodiolar electrode, and 11 ears were implanted with the old perimodiolar electrode. Various electrically-evoked compound action potential (ECAP) metrics were measured to quantify spread of excitation and channel interaction. ECAP threshold and slope were not significantly different among groups. ECAP spread of excitation (SOE) half-width and channel interaction index (CII) were significantly larger in subjects implanted with the lateral wall straight electrodes, indicating a wider spread of excitation compared to those with perimodiolar electrodes. Electrode impedance was significantly lower in subjects implanted with perimodiolar electrodes than those with lateral wall electrodes. Perimodiolar electrode groups yielded significantly narrower SOE half-widths and smaller CII than the lateral wall straight electrode group. This may indicate that the electrode array that hugged the modiolus had less overlap in neural excitation between adjacent electrodes, resulting in reduced channel interaction and potentially better spectral resolution than the electrode array positioned more laterally.

Modulation of Cardiac Ryanodine Receptors by Chloride Intracellular Ion Channel 2

Pathogenic variants of the Chloride intracellular ion channel 2 (CLIC2) are implicated in hypertrophic cardiomyopathy (HCM), a diverse heart condition leading to arrhythmic sudden cardiac death and heart failure. CLIC2 is a unique class of metamorphic protein, related to the enzymatic glutathione s-transferase family and form functional ion channel. Artificial bilayer studies have shown that CLIC2 negatively modulates the activity of cardiac ryanodine receptor 2 (RyR2), implicating the sarcoplasmic/endoplasmic reticulum (SR/ER) Ca2+ release. However, the subsequent consequences of RyR2 and CLIC2 interaction in cardiac physiology remains unknown. Therefore, we ablated clic2 in human induced pluripotent stem cell (hiPSC) line using the CRISPR-Cas9 system and performed cardiomyocyte differentiation. clic2−/− hiPSC-derived cardiomyocytes (hiPSC-CMs) showed altered electrophysiological properties leading to impaired excitation-contraction coupling. clic2−/− hiPSC-CMs showed an increase in beat rate and field potential duration by 143.49±5.96% and 162.43±5.82%, respectively, whereas conduction velocity and spike amplitude decreased by 43.81±2.22% and 43.32±3.54%, respectively compared to WT hiPSC-CMs. Additionally, action potential duration measurements of clic2−/− hiPSC-CMs showed a decrease in APD30, APD50, and APD90 by 74.42%, 65.19%, and 66.46%, respectively compared to WT hiPSC-CMs. Moreover, clic2−/− hiPSC-CMs showed altered Ca2+ handling, with a decrease in peak amplitude (57.07±2.25%) and duration (38.29±1.30%) compared to the WT hiPSC-CMs. The caffeine induced Ca2+ release in clic2−/− hiPSC-CMs, attributed to the SR/ER Ca2+ overload which decreased by 72.19±3.51% compared to WT hiPSC-CMs. Transcriptomics analysis of clic2−/− hiPSC-CMs revealed 223 transcripts with significant changes in expression levels (89 upregulated and 134 downregulated), implicating CLIC2 in hypertrophy cardiomyopathy, dilated cardiomyopathy, and other heart diseases. Furthermore, the protein expression of CLIC2 increases in end-stage failing human heart samples compared to the non-failing heart. In conclusion, our study sheds light on the novel role of CLIC2 in the regulation of cardiac (patho)physiology. National Institutes of Health (NIH) (HL133050, and HL157453); American Heart Association-Transformational Project Award; National Center for advancing translational sciences (TR004178, understudied proteins and druggable targets) (HS). Presidential Predoctoral Fellowship; Margaret T. Nishikawara Merit Scholarship Endowment in Physiology; Graduate School’s Alumni Grants for Graduate Research and Scholarship Program, The Ohio State University (SS). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Through-polymer, via technology-enabled, flexible, lightweight, and integrated devices for implantable neural probes

In implantable electrophysiological recording systems, the headstage typically comprises neural probes that interface with brain tissue and integrated circuit chips for signal processing. While advancements in MEMS and CMOS technology have significantly improved these components, their interconnection still relies on conventional printed circuit boards and sophisticated adapters. This conventional approach adds considerable weight and volume to the package, especially for high channel count systems. To address this issue, we developed a through-polymer via (TPV) method inspired by the through-silicon via (TSV) technique in advanced three-dimensional packaging. This innovation enables the vertical integration of flexible probes, amplifier chips, and PCBs, realizing a flexible, lightweight, and integrated device (FLID). The total weight of the FLIDis only 25% that of its conventional counterparts relying on adapters, which significantly increased the activity levels of animals wearing the FLIDs to nearly match the levels of control animals without implants. Furthermore, by incorporating a platinum-iridium alloy as the top layer material for electrical contact, the FLID realizes exceptional electrical performance, enabling in vivo measurements of both local field potentials and individual neuron action potentials. These findings showcase the potential of FLIDs in scaling up implantable neural recording systems and mark a significant advancement in the field of neurotechnology.

Aminophylline Improves Ventilator-Induced Diaphragmatic Dysfunction by Targeting IGF-1-FOXO1-MURF1 Pathway.

The usage of life-saving mechanical ventilation (MV) could cause ventilator-induced diaphragmatic dysfunction (VIDD), increasing both mortality and morbidity. Aminophylline (AP) has the potential to enhance the contractility of animal skeletal muscle fibers and improve the activity of human respiratory muscles, and the insulin-like growth factor-1 (IGF-1)- forkhead box protein O1 (FOXO1)-muscle RING finger-1 (MURF1) pathway plays a crucial role in skeletal muscle dysfunction. This study aimed to investigate the impact of AP on VIDD and to elucidate the role of the IGF-1-FOXO1-MURF1 pathway as an underlying mechanism. Rat models of VIDD were established through MV treatment. IGF-1 lentiviral (LV) interference (LV-IGF-1-shRNA; controlled by lentiviral negative control LV-NC) was employed to inhibit IGF-1 expression and thereby block the IGF-1-FOXO1-MURF1 pathway. Protein and mRNA levels of IGF-1, FOXO1, and MURF1 were assessed using western blot and real-time reverse transcriptase-polymerase chain reaction (RT-qPCR), respectively. Diaphragm contractility and morphometry were examined through measurement of compound muscle action potentials (CMAPs) and hematoxylin and eosin (H&E) staining. Oxidative stress was evaluated by levels of hydrogen peroxide (H2O2), superoxide dismutase (SOD), antioxidant glutathione (GSH), and carbonylated protein. Mitochondrial stability was assessed by measuring the mitochondrial membrane potential (MMP), and mitochondrial fission and mitophagy were examined through protein levels of dynamin-related protein 1 (DRP1), mitofusin 2 protein (MFN2), phosphatase and tensin homolog (PTEN)-induced kinase 1 (PINK1), and Parkin (western blot). Apoptosis was evaluated using the terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate (UTP) nick-end labeling (TUNEL) assay and levels of Bax, B-cell lymphoma 2 (BCL-2), and Caspase-3. Levels of Atrogin-1, neuronally expressed developmentally downregulated 4 (NEDD4), and muscle ubiquitin ligase of SCF complex in atrophy-1 (MUSA1) mRNA, as well as ubiquitinated protein, were utilized to determine protein degradation. Furthermore, the SUnSET (surface sensing of translation) method was employed to determine rates of protein synthesis. MV treatment upregulated IGF-1 while downregulated FOXO1 and MURF1 (p < 0.05). AP administration reversed IGF-1, FOXO1 and MURF1 (p < 0.05), which was suppressed again by IGF-1 inhibition (p < 0.05), demonstrating the blockage of the IGF-1-FOXO1-MURF1 pathway. MV treatment caused decreased CMAP and cross-sectional areas of diaphragm muscle fibers, and increased time course of CMAP (p < 0.05). Additionally, oxidative stress, cell apoptosis, and protein degradation were increased and mitochondrial stability was decreased by MV treatment (p < 0.05). Conversely, AP administration reversed all these changes induced by MV, but this reversal was disrupted by the blockage of the IGF-1-FOXO1-MURF1 pathway. In this study, MV treatment induced symptoms of VIDD in rats, which were all effectively reversed by AP regulating the IGF-1-FOXO1-MURF1 pathway, demonstrating the potential of AP in ameliorating VIDD.

Evaluation of novel open-source software for cardiac optical mapping

KairoSight-3.0 is a recently released Python-based, open-source software for cardiac optical mapping analysis. Addressing challenges in high-resolution electrophysiological data analysis, KairoSight-3.0 facilitates comprehensive studies of cardiac conduction and excitation-contraction coupling. We compared its performance with ElectroMap, focusing on action potential duration and conduction velocity measurements in mouse heart models subjected to ischaemia and flecainide treatment. Our findings reveal that while both software are effective, inherent methodological differences impact measurement outcomes. KairoSight-3.0's robust analysis capabilities make it a valuable tool in cardiac research. Additionally, future directions for KairoSight-3.0 and other mapping analysis tools are explored. Statement of importanceOpen-source methods for analysis of cardiac optical mapping are vital tools in electrophysiological research. Our work directly evaluates the latest version of KarioSight, recently published in JMCC plus, with ElectroMap, an established and widely used tool. Our results show both software are effective in analysis of changes in both conduction and repolarisation. Considering the new features of KairoSight-3.0 and python implementation, our study importantly demonstrates the effectiveness of the software, highlights potential discrepancies between it and ElectroMap, and provides a perspective on future directions for KairoSight-3.0 and other software.

Injection of IK1 through dynamic clamp can make all the difference in patch-clamp studies on hiPSC-derived cardiomyocytes.

Human-induced stem cell-derived cardiomyocytes (hiPSC-CMs) are a valuable tool for studying development, pharmacology, and (inherited) arrhythmias. Unfortunately, hiPSC-CMs are depolarized and spontaneously active, even the working cardiomyocyte subtypes such as atrial- and ventricular-like hiPSC-CMs, in contrast to the situation in the atria and ventricles of adult human hearts. Great efforts have been made, using many different strategies, to generate more mature, quiescent hiPSC-CMs with more close-to-physiological resting membrane potentials, but despite promising results, it is still difficult to obtain hiPSC-CMs with such properties. The dynamic clamp technique allows to inject a current with characteristics of the inward rectifier potassium current (IK1), computed in real time according to the actual membrane potential, into patch-clamped hiPSC-CMs during action potential measurements. This results in quiescent hiPSC-CMs with a close-to-physiological resting membrane potential. As a result, action potential measurements can be performed with normal ion channel availability, which is particularly important for the physiological functioning of the cardiac SCN5A-encoded fast sodium current (INa). We performed in vitro and in silico experiments to assess the beneficial effects of the dynamic clamp technique in dissecting the functional consequences of the SCN5A-1795insD+/- mutation. In two separate sets of patch-clamp experiments on control hiPSC-CMs and on hiPSC-CMs with mutations in ACADVL and GNB5, we assessed the value of dynamic clamp in detecting delayed afterdepolarizations and in investigating factors that modulate the resting membrane potential. We conclude that the dynamic clamp technique has highly beneficial effects in all of the aforementioned settings and should be widely used in patch-clamp studies on hiPSC-CMs while waiting for the ultimate fully mature hiPSC-CMs.

Correlations between clinical motor scores and CMAP in patients with type 2 spinal muscular amyotrophy treated with nusinersen

BackgroundSpinal muscular atrophy (SMA) is a neuromuscular disorder characterized by the degeneration of the anterior horn cells of the spinal cord. Nusinersen for the treatment of SMA has been covered by public healthcare in France since May 2017. ObjectiveOur aim was to investigate whether there is a correlation between clinical and compound motor action potential (CMAP) measurements in SMA patients treated with nusinersen after 3 years’ follow-up. MethodMotor skills were evaluated regularly between M0 and M36 using the Motor Function Measure (MFM) score. CMAP measurements were collected regularly between M0 and M22. ResultsData for 10 patients with SMA type 2 were collected and divided into two age groups (< 5 years and > 5 years). Motor function improved, but not significantly, regarding distal motor skills (D3) in both groups, and in axial and proximal motor function (D2) in the younger group. CMAP measurements improved in all patients. CMAP increased significantly for the median nerve, and this improvement correlated significantly with global MFM and with axial and proximal tone (D2). ConclusionOur study shows gain in distal motor function with nusinersen, especially in younger patients with SMA type 2. These results encourage the screening of SMA patients and treatment as early as possible. CMAP measurements of the median nerve show clear improvement in patients treated with nusinersen and could be performed as routine follow-up.

CNSC-28. CELLULAR AND FUNCTIONAL REMODELING OF HUMAN CEREBRAL ORGANOIDS BY GLIOBLASTOMA STEM-LIKE CELLS

Abstract The burgeoning field of cancer neuroscience focuses on deciphering the role of normal neural cells in brain tumor growth. Until recently, representation of normal human neural cells in brain tumor model systems was lacking. By utilizing human induced-pluripotent stem cells derived cerebral organoids (COs) co-cultured with glioblastoma stem-like cells (RFP-luciferase tagged MDA-GSCs, n = 3 representing each glioblastoma molecular sub-type), we investigated the effects of GSCs on CO-derived neural cells and their activity. COs and CO+MDA-GSCs were subjected to single-cell RNA-sequencing (scRNA-seq). As per typical micro-anatomy of COs, neural stem/progenitor cells are interiorly distributed whereas differentiated neurons are positioned on the surfaces, enabling measurement of neuronal action potential on surfaces of COs by micro-electrode arrays (MEA). The scRNA-seq data from CO+MDA-GSC samples were subset into CO-derived (luciferase-ve) and GSCs-derived (luciferase+ve). Compared with COs, co-cultured samples had significantly higher percentage of non-telencephalon neural progenitor cells (ntNPCs) (CO_vs._CO+MDA-GSC(luciferase-ve): 15.6% vs. 47.2%-63.4%) while the percentages of cortical NPC (cNPCs) and intermediate progenitors (IPs) was lower (CO_vs._CO+MDA-GSC(luciferase-ve): 39.2% vs. 12.0%-20.5%). These alterations in NPC/IPs abundance were accompanied by decreased proportions of cortical excitatory neurons (CO_vs._CO+MDA-GSC(Luciferase-ve): 33.2% vs. 7.9%-23.4%). Among luciferase+ve MDA-GSCs-derived cells in co-culture samples, mesenchymal MDA-GSCs had higher abundance of ntNPCs versus cNPCs (30.4% versus 63.6%) whereas, among classical and proneural MDA-GSCs ntNPCs were 11.45-22.8 times higher. Interestingly, 14.9% of proneural MDA-GSCs derived cells displayed inhibitory neuron signatures. After 3 weeks, the mean firing rate measured by MEA was significantly lower in co-cultures compared to COs (CO_vs._CO+MDA-GSC: 0.052 Hz vs. 0.0081 Hz p-value 0.000219), suggesting functional remodeling. Our results show that cellular remodeling of normal cells resulted in progenitor-like cell-state whereas that of MDA-GSCs varied across molecular sub-type. These results suggest interactions between normal and tumor cells can potentially be leveraged to manage brain tumor growth and its impact on normal brain.

DualSort: online spike sorting with a running neural network

Objective. Spike sorting, i.e. the detection and separation of measured action potentials from different extracellularly recorded neurons, remains one of the bottlenecks in deciphering the brain. In recent years, the application of neural networks (NNs) for spike sorting has garnered significant attention. Most methods focus on specific sub-problems within the conventional spike sorting pipeline, such as spike detection or feature extraction, and attempt to solve them with complex network architectures. This paper presents DualSort, a simple NN that gets combined with downstream post-processing for real-time spike sorting. It shows high efficiency, low complexity, and requires a comparatively small amount of human interaction. Approach. Synthetic and experimentally obtained extracellular single-channel recordings were utilized to train and evaluate the proposed NN. For training, spike waveforms were labeled with respect to their associated neuron and position in the signal, allowing the detection and categorization of spikes in unison. DualSort classifies a single spike multiple times in succession, as it runs over the signal in a step-by-step manner and uses a post-processing algorithm that transmits the network output into spike trains. Main results. With the used datasets, DualSort was able to detect and distinguish different spike waveforms and separate them from background activity. The post-processing algorithm significantly strengthened the overall performance of the model, making the system more robust as a whole. Although DualSort is an end-to-end solution that efficiently transforms filtered signals into spike trains, it competes with contemporary state-of-the-art technologies that exclusively target single sub-problems in the conventional spike sorting pipeline. Significance. This work demonstrates that even under high noise levels, complex NNs are not necessary by any means to achieve high performance in spike detection and sorting. The utilization of data augmentation on a limited quantity of spikes could substantially decrease hand-labeling compared to other studies. Furthermore, the proposed framework can be utilized without human interaction when combined with an unsupervised technique that provides pseudo labels for DualSort. Due to the low complexity of our network, it works efficiently and enables real-time processing on basic hardware. The proposed approach is not limited to spike sorting, as it may also be used to process different signals, such as electroencephalogram (EEG), which needs to be investigated in future research.

Effect of a Single Dose of Oxaliplatin on the Induction of Peripheral Neuropathy in a Rat Model: An in Vivo Electrophysiological Study.

The anticancer drug oxaliplatin is associated with peripheral neuropathy as a side effect accompanied by mechanical and cold allodynia. Although the superficial layer of the spinal cord dorsal horn is known to receive information primarily from peripheral pain nerves, to our knowledge, no in vivo electrophysiological analyses have been conducted to determine whether oxaliplatin administration increases the excitability of superficial layer neurons. Therefore, in vivo extracellular recordings were performed to measure action potentials in the deep and superficial layers of the spinal cord dorsal horn in rats treated with a single dose (6 mg/kg) of oxaliplatin. Action potentials were produced by mechanical stimulation with von Frey filaments to the hindlimb receptive fields. The results revealed that the firing frequency of action potentials increased relative to the intensity of mechanical stimulation, and that both deep and superficial layer neurons in the spinal cord dorsal horn increased significantly in oxaliplatin-treated compared with vehicle-treated rats, especially in the superficial layer. Several superficial layer neurons showed spontaneous firing that was not seen in vehicle-treated rats. In addition, a clear increase was seen in the firing frequency of neurons in the superficial layer of oxaliplatin-treated rats in response to a cold stimulus (here, the addition of acetone to the hindlimb receptive field). This study suggests that the superficial spinal cord dorsal horn strongly reflects the pain pathophysiology in peripheral neuropathy induced by oxaliplatin administration, and that the superficial layer neurons are useful for in vivo electrophysiological analysis using this pathological model.

Using macular velocity measurements to relate parameters of bone conduction to vestibular compound action potential responses

To examine mechanisms responsible for vestibular afferent sensitivity to transient bone conducted vibration, we performed simultaneous measurements of stimulus-evoked vestibular compound action potentials (vCAPs), utricular macula velocity, and vestibular microphonics (VMs) in anaesthetized guinea pigs. Results provide new insights into the kinematic variables of transient motion responsible for triggering mammalian vCAPs, revealing synchronized vestibular afferent responses are not universally sensitive to linear jerk as previously thought. For short duration stimuli (< 1 ms), the vCAP increases magnitude in close proportion to macular velocity and temporal bone (linear) acceleration, rather than other kinematic elements. For longer duration stimuli, the vCAP magnitude switches from temporal bone acceleration sensitive to linear jerk sensitive while maintaining macular velocity sensitivity. Frequency tuning curves evoked by tone-burst stimuli show vCAPs increase in proportion to onset macular velocity, while VMs increase in proportion to macular displacement across the entire frequency bandwidth tested between 0.1 and 2 kHz. The subset of vestibular afferent neurons responsible for synchronized firing and vCAPs have been shown previously to make calyceal synaptic contacts with type I hair cells in the striolar region of the epithelium and have irregularly spaced inter-spike intervals at rest. Present results provide new insight into mechanical and neural mechanisms underlying synchronized action potentials in these sensitive afferents, with clinical relevance for understanding the activation and tuning of neurons responsible for driving rapid compensatory reflex responses.

Sensitivity and specificity of phrenic nerve electrophysiology to predict mechanical ventilation in the Guillain-Barré syndrome.

In Guillain-Barré syndrome (GBS), the sensitivity and specificity of phrenic compound muscle action potential (CMAP) measurements to predict endotracheal mechanical ventilation are unknown. Hence, we sought to estimate sensitivity and specificity. We performed a 10-year retrospective analysis of adult GBS patients from our single-center laboratory database (2009 to 2019). The phrenic nerve amplitudes and latencies before ventilation were recorded along with other clinical and demographic features. Receiver operating curve (ROC) analysis with area under the curve (AUC) was used to determine the sensitivity and specificity with 95% confidence interval (CI) for phrenic amplitudes and latencies in predicting the need for mechanical ventilation. Two hundred five phrenic nerves were analyzed in 105 patients. The mean age was 46.1 ± 16.2 years, with 60% of them being male. Fourteen patients (13.3%) required mechanical ventilation. The average phrenic amplitudes were lower in the ventilated group (P = .003), but average latencies did not differ (P = .133). ROC analysis confirmed that phrenic amplitudes could predict respiratory failure (AUC = 0.76; 95% CI, 0.61 to 0.91; P < .002), but phrenic latencies could not (AUC = 0.60; 95% CI, 0.46 to 0.73; P = .256). The best threshold for amplitude was ≥0.6 mV, with sensitivity, specificity, and positive and negative predictive values of 85.7%, 58.2%, 24.0%, and 96.4%, respectively. Our study suggests that phrenic CMAP amplitudes can predict the need for mechanical ventilation in GBS. In contrast, phrenic CMAP latencies are not reliable. The high negative predictive value of phrenic CMAP amplitudes ≥0.6 mV can preclude mechanical ventilation, making these a useful adjunct to clinical decision-making.

Relation between electrical compound action potential measures and speech perception in cochlear implanted children: audiological and phonological outcomes

PurposeTo study ECAP measures (threshold and amplitude growth function 'AGF') in children CI users and find the relation between these ECAP measures and speech outcomes using audiological and phonological assessment.Subjects and methodTwenty-one children were unilaterally implanted with Medel CI, and all subjects were submitted to phonological assessment, basic audiological assessment, speech recognition tests (WRS and BKB-SIN) and Medel maestro software measures (IFT, AutoART and AGF measures "thresholds and slopes" across apical, middle and basal electrodes).ResultsThis study demonstrated no statistically significant difference between AGF thresholds at apical, middle and basal electrodes and a statistically significant difference between AGF slopes at apical and both middle and basal electrodes. There was no statistically significant correlation between the ECAP threshold and speech perception tests. In contrast, a positive statistically significant correlation was found between the AGF slope of the apical electrode and word recognition score, and a negative statistically significant correlation between AGF slopes at apical, middle and basal electrodes and SNR loss of BKB-SIN. High sensitivity and specificity of AGF slope at apical electrode were found to differentiate between good and poor performers as regards SNR loss of BKB-SIN and language test.ConclusionsThe AGF slope reflects neural survival better than the ECAP threshold. AGF slope at apical electrodes correlated with better CI performance in both phoniatric and audiological measures of speech perception and can be used as an objective tool to predict CI outcome.

A 512-Ch Dual-Mode Microchip for Simultaneous Measurements of Electrophysiological and Neurochemical Activities

In the study of the brain, large and high-density microelectrode arrays have been widely used to study the behavior of neurotransmission. CMOS technology has facilitated these devices by enabling the integration of high-performance amplifiers directly on-chip. Usually, these large arrays measure only the voltage spikes resulting from action potentials traveling along firing neuronal cells. However, at synapses, communication between neurons occurs by the release of neurotransmitters, which cannot be measured on typical CMOS electrophysiology devices. Development of electrochemical amplifiers has resulted in the measurement of neurotransmitter exocytosis down to the level of a single vesicle. To effectively monitor the complete picture of neurotransmission, measurement of both action potentials and neurotransmitter activity is needed. Current efforts have not resulted in a device that is capable of the simultaneous measurement of action potential and neurotransmitter release at the same spatiotemporal resolution needed for a comprehensive study of neurotransmission. In this paper, we present a true dual-mode CMOS device that fully integrates 256-ch electrophysiology amplifiers and 256-ch electrochemical amplifiers, along with an on-chip 512 electrode microelectrode array capable of simultaneous measurement from all 512 channels.

Small Molecule Positive Modulator of Hepatocyte Growth Factor (HGF)/MET, ATH-1105, Improves Function and Reduces Disease Biomarkers in a TDP-43 Mouse Model of Amyotrophic Lateral Sclerosis (P8-8.007)

<h3>Objective:</h3> Evaluate the preclinical efficacy of the small molecule positive modulator of hepatocyte growth factor (HGF)/MET, ATH-1105, in a mouse model of amyotrophic lateral sclerosis (ALS). <h3>Background:</h3> Activation of the MET receptor by HGF promotes neuroprotective, neurotrophic, and anti-inflammatory mechanisms. Small molecule positive modulators of HGF/MET, including ATH-1105, have been developed to explore the therapeutic potential of this target. ALS is characterized by progressive motor neuron degeneration and demyelination, accompanied by systemic inflammation and pathological aggregation of TAR DNA-binding protein 43 (TDP-43) in 97% of patients. We hypothesized that treatment with ATH-1105 would be beneficial in a TDP-43 mouse model of ALS. <h3>Design/Methods:</h3> ATH-1105 at 10 or 20 mg/kg was orally administered daily to male Prp-TDP43_A315T mice (n=10/group) for two months. At baseline and after one and two months of treatment, we conducted a battery of motor behavior tests, and assessed sciatic nerve health by compound muscle action potential (CMAP) and nerve conduction velocity (NCV) measurements. Plasma biomarkers of inflammation (IL-6, TNF-α) and neurodegeneration (neurofilament light chain [NfL]) were interrogated after one and two months of treatment. Sciatic nerves were stained for quantification of axonal and myelin parameters as well as phospho-TDP-43 aggregation at study termination. <h3>Results:</h3> The deterioration of motor function in TDP-43 animals was significantly mitigated in a dose-dependent manner after treatment with ATH-1105, and significant functional improvement of sciatic nerve conduction was observed. Additionally, plasma levels of all biomarkers assessed were significantly decreased, indicating reduced systemic inflammation and neurodegeneration in treated TDP-43 mice. Sciatic nerve histology revealed a protection of motor axon numbers and myelination, as well as a reduction in axonal phospho-TDP-43 aggregation by ATH-1105. <h3>Conclusions:</h3> ATH-1105 was found to be protective across a multitude of functional and structural measures of ALS disease progression. These findings support the continued development of this small molecule positive modulator of HGF/MET for ALS. <b>Disclosure:</b> Mrs. Kleist has received personal compensation for serving as an employee of Athira Pharma. Mrs. Kleist has received personal compensation for serving as an employee of Alpine Immune Sciences. Mrs. Kleist has stock in Athira Pharma. Mrs. Kleist has stock in Alpine Immune Sciences. Dr. Berthiaume has received personal compensation for serving as an employee of Athira Pharma. Dr. Berthiaume has stock in Athira Pharma. An immediate family member of Dr. Berthiaume has stock in Athira Pharma. Dr. Johnston has received personal compensation for serving as an employee of Athira Pharma, Inc. Dr. Johnston has stock in Athira Pharma, Inc. An immediate family member of Dr. Johnston has stock in Athira Pharma, Inc. Dr. Johnston has received intellectual property interests from a discovery or technology relating to health care. Dr. Reda has received personal compensation for serving as an employee of Athira Pharma, Inc. . Dr. Reda has stock in Athira Pharma, Inc. . Dr. Moebius has received personal compensation in the range of $100,000-$499,999 for serving as an officer or member of the Board of Directors for Athira Pharma, Inc.. Dr. Moebius has stock in Athira Pharma, Inc.. Dr. Church has received personal compensation for serving as an employee of Athira Pharma. Dr. Church has stock in Athira Pharma. Dr. Church has received intellectual property interests from a discovery or technology relating to health care.

Enhanced endoplasmic reticulum RyR1 receptor phosphorylation leads to diaphragmatic dysfunction in septic rats

To explore the role of endoplasmic reticulum ryanodine receptor 1 (RyR1) expression and phosphorylation in sepsis- induced diaphragm dysfunction. Thirty SPF male SD rats were randomized equally into 5 groups, including a sham-operated group, 3 sepsis model groups observed at 6, 12, or 24 h following cecal ligation and perforation (CLP; CLP-6h, CLP-12h, and CLP-24h groups, respectively), and a CLP-24h group with a single intraperitoneal injection of KN- 93 immediately after the operation (CLP-24h+KN-93 group). At the indicated time points, diaphragm samples were collected for measurement of compound muscle action potential (CMAP), fatigue index of the isolated diaphragm and fitted frequencycontraction curves. The protein expression levels of CaMK Ⅱ, RyR1 and P-RyR1 in the diaphragm were detected using Western blotting. In the rat models of sepsis, the amplitude of diaphragm CMAP decreased and its duration increased with time following CLP, and the changes were the most obvious at 24 h and significantly attenuated by KN-93 treatment (P < 0.05). The diaphragm fatigue index increased progressively following CLP (P < 0.05) irrespective of KN- 93 treatment (P>0.05). The frequency-contraction curve of the diaphragm muscle decreased progressively following CLP, and was significantly lower in CLP-24 h group than in CLP-24 h+KN-93 group (P < 0.05). Compared with that in the sham-operated group, RyR1 expression level in the diaphragm was significantly lowered at 24 h (P < 0.05) but not at 6 or 12 following CLP, irrespective of KN-93 treatment; The expression level of P-RyR1 increased gradually with time after CLP, and was significantly lowered by KN-93 treatment at 24 h following CLP (P < 0.05). The expression level of CaMKⅡ increased significantly at 24 h following CLP, and was obviously lowered by KN-93 treatment (P < 0.05). Sepsis causes diaphragmatic dysfunction by enhancing CaMK Ⅱ expression and RyR1 receptor phosphorylation in the endoplasmic reticulum of the diaphragm.

Clinical, electrophysiological, and histomorphological effects of local coenzyme Q10 and vitamin E use in a rat model of peripheral nerve injury.

This study aimed to investigate the clinical, electrophysiological, and histomorphological effects of local use of coenzyme Q10 and vitamin E combination in a rat model of peripheral nerve injury. Forty adult female Wistar-Albino rats weighing 250-350 g were kept in a room with a temperature of 20-22°C and a light/dark cycle of 12 hours. They had free access to food and water. The right sciatic nerves of 40 rats were transected and repaired. Subjects were divided into 4 groups: controls (control-4 weeks and control-8 weeks) and treatments (treatment-4 weeks and treatment-8 weeks). A combination of coenzyme Q10 and vitamin E was applied to the repair site by a catheter placed subcutaneously in the treatment group. Only transection-repair was done in the control group. All groups were divided into 2 subgroups for histomorphological, clinical, and electrophysiological experiments because of concerns about possible interference with histomorphological preparation (5 rats in each group). The experiment results were examined by the thermal plantar test, action potential and latency time measurements, and electron microscopy at the end of 4 and 8 weeks. The intact group was studied as the uninterrupted 10 left sciatic nerves of control for 4 weeks. The mean thermal plantar test results of the intact group were better than those of the control groups (P < .05). However, there was no significant difference between the intact and treatment groups. In the histomorphological examination, the number of myelinated axons increased significantly, and the myelin structure was closer to that of the intact group, especially when the treatment-8 group was compared with the control groups (control-4: P < .0001, control-8: P < .01). Local use of coenzyme Q10 and vitamin E seems useful in the experimental rat sciatic nerve transection-repair model.