Spontaneous Electrical Activity Research Articles

Characterization of Developmental Changes in Spontaneous Electrical Activity of Medial Superior Olivary Neurons Before Hearing Onset With a Combination of Injectable and Volatile Anesthesia.

In this work the impact of two widely used anesthetics on the electrical activity of auditory brainstem neurons was studied during postnatal development. Spontaneous electrical activity in neonate rats of either sex was analyzed through a ventral craniotomy in mechanically ventilated pups to carry out patch clamp and multi-electrode electrophysiology recordings in the medial region of the superior olivary complex (SOC) between birth (postnatal day 0, P0) and P12. Recordings were obtained in pups anesthetized with the injectable mix of ketamine/xylazine (K/X mix), with the volatile anesthetic isoflurane (ISO), or in pups anesthetized with K/X mix that were also exposed to ISO. The results of patch clamp recordings demonstrate for the first time that olivary and periolivary neurons in the medial region of the SOC fire bursts of action potentials. The results of multielectrode recordings suggest that the firing pattern of single units recorded in K/X mix is similar to that recorded in ISO anesthetized rat pups. Taken together, the results of this study provide a framework to use injectable and volatile anesthetics for future studies to obtain functional information on the activity of medial superior olivary neurons in vivo.

Influence of sex on intracellular calcium homoeostasis in patients with atrial fibrillation

AimsAtrial fibrillation (AF) has been associated with intracellular calcium disturbances in human atrial myocytes, but little is known about the potential influence of sex and we here aimed to address this issue.Methods and resultsAlterations in calcium regulatory mechanisms were assessed in human atrial myocytes from patients without AF or with long-standing persistent or permanent AF. Patch-clamp measurements revealed that L-type calcium current (ICa) density was significantly smaller in males with than without AF (−1.15 ± 0.37 vs. −2.06 ± 0.29 pA/pF) but not in females with AF (−1.88 ± 0.40 vs. −2.21 ± 0.0.30 pA/pF). In contrast, transient inward currents (ITi) were more frequent in females with than without AF (1.92 ± 0.36 vs. 1.10 ± 0.19 events/min) but not in males with AF. Moreover, confocal calcium imaging showed that females with AF had more calcium spark sites than those without AF (9.8 ± 1.8 vs. 2.2 ± 1.9 sites/µm2) and sparks were wider (3.0 ± 0.3 vs. 2.2 ± 0.3 µm) and lasted longer (79 ± 6 vs. 55 ± 8 ms), favouring their fusion into calcium waves that triggers ITIs and afterdepolarizations. This was linked to higher ryanodine receptor phosphorylation at s2808 in women with AF, and inhibition of adenosine A2A or beta-adrenergic receptors that modulate s2808 phosphorylation was able to reduce the higher incidence of ITI in women with AF.ConclusionPerturbations of the calcium homoeostasis in AF is sex-dependent, concurring with increased spontaneous SR calcium release-induced electrical activity in women but not in men, and with diminished ICa density in men only.

96101 Temporal Evolution of Neural Activity in Human Brain Organoids

ABSTRACT IMPACT: This study will provide the essential characterization of intrinsic neural activity in human brain organoids, both at the single cell and network levels, to harness for translational purposes. OBJECTIVES/GOALS: Brain organoids are 3D, stem cell-derived neural tissues that recapitulate neurodevelopment. However, to levy their full translational potential, a deeper understanding of their intrinsic neural activity is essential. Here, we present our preliminary analysis of maturing neural activity in human forebrain organoids. METHODS/STUDY POPULATION: Forebrain organoids were generated from human iPSC lines derived from healthy volunteers. Linear microelectrode probes were employed to record spontaneous electrical activity from day 77, 100, and 130 organoids. Single unit recordings were collected during hour-long recordings, involving baseline recordings followed by glutamatergic blockade. Subsequently, tetrodotoxin, was used to abolish action potential firing. Single units were identified via spike sorting, and the spatiotemporal evolution of baseline neural properties and network dynamics was characterized. RESULTS/ANTICIPATED RESULTS: Nine organoids were recorded successfully (n=3 per timepoint). A significant difference in number of units was seen across age groups (F (2,6) = 6.4178, p = 0.0323). Post hoc comparisons by the Tukey HSD test showed significantly more units in day 130 (51.67 ±14.15) than day 77 (16.33 ±14.98) organoids. Mean firing rates were significantly different in organoids based on age, with drug condition also trending toward significance (F (6,12) = 9.97; p = 0.0028 and p = 0.08 respectively). Post hoc comparisons showed a higher baseline firing rate in day 130 (0.99Hz ±0.30) organoids than their day 77 counterparts at baseline (0.31Hz ±0.066) and glutamate blockade (0.31Hz ±0.045). Preliminary network analysis showed no modularity or small-world features; however, these features are expected to emerge as organoids mature. DISCUSSION/SIGNIFICANCE OF FINDINGS: Initial analysis of brain organoid activity demonstrates changes in single unit properties as they mature. Additional work in this area, as well as further network analyses, will confer better sense of how to rationally utilize brain organoids for translational purposes.

Delta brushes are not just a hallmark of EEG in human preterm infants.

The delta brush, a well-known characteristic waveform of the human preterm electroencephalogram, represents spontaneous electrical activity. Recent experimental animal model evidence suggests that delta brushes are not only spontaneous intrinsic activity but are also evoked by external sensory stimulation or spontaneous movement. They are also likely to reflect the activity of subplate neurons, which play an important role in early brain development and network organization. Here, evidence about delta brushes in human preterm electroencephalogram is provided along with future perspectives.

Purinergic Signaling Controls Spontaneous Activity in the Auditory System throughout Early Development.

Spontaneous bursts of electrical activity in the developing auditory system arise within the cochlea before hearing onset and propagate through future sound-processing circuits of the brain to promote maturation of auditory neurons. Studies in isolated cochleae revealed that this intrinsically generated activity is initiated by ATP release from inner supporting cells (ISCs), resulting in activation of purinergic autoreceptors, K+ efflux, and subsequent depolarization of inner hair cells. However, it is unknown when this activity emerges or whether different mechanisms induce activity during distinct stages of development. Here we show that spontaneous electrical activity in mouse cochlea from both sexes emerges within ISCs during the late embryonic period, preceding the onset of spontaneous correlated activity in inner hair cells and spiral ganglion neurons, which begins at birth and follows a base to apex developmental gradient. At all developmental ages, pharmacological inhibition of P2Y1 purinergic receptors dramatically reduced spontaneous activity in these three cell types. Moreover, in vivo imaging within the inferior colliculus revealed that auditory neurons within future isofrequency zones exhibit coordinated neural activity at birth. The frequency of these discrete bursts increased progressively during the postnatal prehearing period yet remained dependent on P2RY1. Analysis of mice with disrupted cholinergic signaling in the cochlea indicate that this efferent input modulates, rather than initiates, spontaneous activity before hearing onset. Thus, the auditory system uses a consistent mechanism involving ATP release from ISCs and activation of P2RY1 autoreceptors to elicit coordinated excitation of neurons that will process similar frequencies of sound.SIGNIFICANCE STATEMENT In developing sensory systems, groups of neurons that will process information from similar sensory space exhibit highly correlated electrical activity that is critical for proper maturation and circuit refinement. Defining the period when this activity is present, the mechanisms responsible and the features of this activity are crucial for understanding how spontaneous activity influences circuit development. We show that, from birth to hearing onset, the auditory system relies on a consistent mechanism to elicit correlate firing of neurons that will process similar frequencies of sound. Targeted disruption of this activity will increase our understanding of how these early circuits mature and may provide insight into processes responsible for developmental disorders of the auditory system.

Dynamic Clamp in Electrophysiological Studies on Stem Cell-Derived Cardiomyocytes-Why and How?

Human pluripotent stem cell-derived cardiomyocytes (hPSC-CMs) are supposed to be a good human-based model, with virtually unlimited cell source, for studies on mechanisms underlying cardiac development and cardiac diseases, and for identification of drug targets. However, a major drawback of hPSC-CMs as a model system, especially for electrophysiological studies, is their depolarized state and associated spontaneous electrical activity. Various approaches are used to overcome this drawback, including the injection of "synthetic" inward rectifier potassium current (IK1), which is computed in real time, based on the recorded membrane potential ("dynamic clamp"). Such injection of an IK1-like current results in quiescent hPSC-CMs with a nondepolarized resting potential that show "adult-like" action potentials on stimulation, with functional availability of the most important ion channels involved in cardiac electrophysiology. These days, dynamic clamp has become a widely appreciated electrophysiological tool. However, setting up a dynamic clamp system can still be laborious and difficult, both because of the required hardware and the implementation of the dedicated software. In the present review, we first summarize the potential mechanisms underlying the depolarized state of hPSC-CMs and the functional consequences of this depolarized state. Next, we explain how an existing manual patch clamp setup can be extended with dynamic clamp. Finally, we shortly validate the extended setup with atrial-like and ventricular-like hPSC-CMs. We feel that dynamic clamp is a highly valuable tool in the field of cellular electrophysiological studies on hPSC-CMs and hope that our directions for setting up such dynamic clamp system may prove helpful.

Neuronal excitability and sensory responsiveness in the thalamo-cortical network in a novel rat model of isoelectric brain state.

The neuronal and network properties that persist during an isoelectric coma remain largely unknown. We developed a new in vivo rat model to assess cell excitability and sensory responsiveness in the thalamo-cortical pathway during an isoflurane-induced isoelectric brain state. The isoelectric electrocorticogram reflected a complete interruption of spontaneous synaptic and firing activities in cortical and thalamic neurons. Cell excitability and sensory responses in the thalamo-cortical network persisted at a reduced level in the isoelectric condition and returned to control values after resumption of background brain activity. These findings could lead to a reassessment of the functional status of the drug-induced isoelectric state: a latent state in which individual neurons and networks retain to some extent the ability of being activated by external inputs. The neuronal and network properties that persist in an isoelectric brain completely deprived of spontaneous electrical activity remain largely unexplored. Here, we developed a new in vivo rat model to examine cell excitability and sensory responsiveness in somatosensory thalamo-cortical networks during the interruption of endogenous brain activity induced by high doses of isoflurane. Electrocorticograms (ECoGs) from the barrel cortex were captured simultaneously with either intracellular recordings of subjacent cortical pyramidal neurons or extracellular records of the related thalamo-cortical neurons. Isoelectric ECoG periods reflected the disappearance of spontaneous synaptic and firing activities in cortical and thalamic neurons. This was associated with a sustained membrane hyperpolarization and a reduced intrinsic excitability in deep-layer cortical neurons, without significant changes in their membrane input resistance. Concomitantly, we found that whisker-evoked potentials in the ECoG and synaptic responses in cortical neurons were attenuated in amplitude and increased in latency. Impaired responsiveness in the barrel cortex paralleled with a lowering of the sensory-induced firing in thalamic cells. The return of endogenous brain electrical activities, after reinstatement of a control isoflurane concentration, led to the recovery of cortical neurons excitability and sensory responsiveness. These findings demonstrate the persistence of a certain level of cell excitability and sensory integration in the isoelectric state and the full recovery of cortico-thalamic functions after restoration of internal cerebral activities.

Experience using multielectrode cardiac catheters for detection of electrophysiologic activity of the human urinary bladder.

To determine the feasibility of commercially available multielectrode cardiac electrophysiology catheters to detect electrical activity in the human bladder. Ten subjects requiring cystoscopy for the evaluation of lower urinary tract pathology were eligible for participation in our study. After routine rigid cystoscopy with a 70° cystoscope, various multielectrode cardiac electrophysiology catheters were introduced into the bladder. One of three catheters with different electrode configurations was used per subject. Electroanatomical images of the bladder were created and spontaneous electrical activity was recorded. Subjective response to electrical stimuli delivered across the electrodes (20 mA at 5 ms pulse width, rate 100 ms) was also recorded. The responses were qualitatively compared with that from a prior study. Electrical activity recorded at the dome of the bladder was less than 0.5 mV and low frequency. Myopotentials resembling smooth muscle were detected at electrodes near or within the trigone. A sensory response was reported with the use of pacing stimuli, with the sensation in the trigone being reported more often than the dome of the bladder. Stimulation in the trigone triggered sensory urgency and voiding in a patient with a history of overactive bladder. The use of multielectrode catheters to measure human bladder electrophysiologic activity is feasible. Issues with noise reduction still exist, though to a lesser extent with the multielectrode basket design than simple quadripolar one. Sensory responses to pacing stimuli may be useful for diagnostic and therapeutic purposes in the future.

Pathophysiological mechanisms of neurological disorders in experimental animals exposed to vibration

The review presents an analysis of literature on the study of nervous system changes in experimental animals exposed to vibration. The hypoxic type of cellular metabolism against the background of vibration is the result of vascular mechanoreceptors stimulation and spasm of blood vessels as well as intravascular pressure phase fluctuations and impaired blood and lymph outflow. Hemodynamic disorders and microangiopathy in the central nervous system can reach the level of cerebral vascular impairment and capillary-trophic insufficiency of the brain. Changes in calcium homeostasis at the cellular and tissue levels is a key mechanism of neuronal destruction occurring alongside with impaired blood supply to the nervous tissue in patients with vibrational disease. Long-term exposure to vibration results in reduced tissue respiration in the brain structures of experimental animals, that is most pronounced in the cortex and leads to a pathological change of spontaneous electrical activity of brain structures. Acute vibration stress stimulated the synthesis and excretion of serotonin not only in the hippocampus and hypothalamus but also in the cerebellum, which explains the disturbances of the oculomotor reactions observed in vibration exposure in the control system of the vertical vestibular ocular reflex. A decrease in the total number of neurons as well as an increase in the number of astroglia cells against the background of paravascular tissue edema were revealed against the background of changes in neurotransmitters levels. An increase in the concentration of the biomarker of structural and functional damage to brain tissue specific protein S-100B accompanies the development of professional sensorineural hearing loss and dysfunction of cerebral level vegetative regulation.

Integrating biokinetics and in vitro studies to evaluate developmental neurotoxicity induced by chlorpyrifos in human iPSC-derived neural stem cells undergoing differentiation towards neuronal and glial cells

For some complex toxicological endpoints, chemical safety assessment has conventionally relied on animal testing. Apart from the ethical issues, also scientific considerations have been raised concerning the traditional approach, highlighting the importance for considering real life exposure scenario. Implementation of flexible testing strategies, integrating multiple sources of information, including in vitro reliable test methods and in vitro biokinetics, would enhance the relevance of the obtained results. Such an approach could be pivotal in the evaluation of developmental neurotoxicity (DNT), especially when applied to human cell-based models, mimicking key neurodevelopmental processes, relevant to human brain development.Here, we integrated the kinetic behaviour with the toxicodynamic alterations of chlorpyrifos (CPF), such as in vitro endpoints specific for DNT evaluation, after repeated exposure during differentiation of human neural stem cells into a mixed culture of neurons and astrocytes. The upregulation of some cytochrome P450 and glutathione S-transferase genes during neuronal differentiation and the formation of the two major CPF metabolites (due to bioactivation and detoxification) supported the metabolic competence of the used in vitro model. The alterations in the number of synapses, neurite outgrowth, brain derived neurotrophic factor, the proportion of neurons and astrocytes, as well as spontaneous electrical activity correlated well with the CPF ability to enter the cells and be bioactivated to CPF-oxon. Overall, our results confirm that combining in vitro biokinetics and assays to evaluate effects on neurodevelopmental endpoints in human cells should be regarded as a key strategy for a quantitative characterization of DNT effects.

Activity Evaluation of Facial Muscles by Surface Electromyography.

Background:Surface electromyography (sEMG) is an easy, noninvasive, and reproducible way to assess spontaneous electrical activity of muscles in real time. In this study, we report data on the correlation between sEMG and mimetic muscle activity during specific tasks so as to create a case–control reference for future studies on acute, chronic, and congenital facial palsy.Methods:Twelve healthy participants were enrolled (6 women and 6 men) with a mean age of 42.75 (range, 26–58 years) years. sEMG signals were recorded at rest and while performing voluntary and specific tasks that elicited selective contraction of frontalis, orbicularis oculi, zygomaticus major, orbicularis oris, and platysma muscles simultaneously and bilaterally for each muscle group. Statistical analysis was performed to evaluate if there was a statistically significant difference of the average contraction values between left- and right-side data sets and between male and female participants.Results:No statistically significant difference was found between male and female participants or between the right and left sides at rest and while performing the requested tasks, even though they were not identical. No participant complained about the procedure.Conclusions:Interindividual and intraindividual variability of the sEMG signal as well as crosstalk between muscles groups were reported downsides that we did not encounter. The absolute noninvasiveness of our procedure makes it feasible to be applied even to young children. This dataset obtained in healthy participants might also be useful in the observation of patients undergoing regeneration/reinnervation procedure following recently acquired facial palsy or mimetic muscle reconstruction for congenital/inveterate one.

Implementation of High Performance EEG Based Seizure Detection And Analysis On Multicore Platform

About 50 million people worldwide suffer from epilepsy, the neurological disorder characterized by seizures. The primary tool for diagnosis of an epileptic seizure is an electroencephalography (EEG) which records the brain’s spontaneous electrical activity. This requires the placement of a minimum of 16 electrodes on the scalp with each electrode being interpreted as a channel. The classification of seizure detection and analysis techniques mainly work in two stages, where features are extracted from raw EEG data in the first stage and then the obtained features are used as input for the classification process in the second stage. Traditionally the Seizure detection algorithms were implemented using DSP Processor or FPGAs. But these single core platforms are constrained with respect to speed of operation and power consumption. There is a greater need to reduce the power consumption as well to increase the speed of EEG seizure detection system. This problem can be addressed using the Multicore Processors, which process data simultaneously. This project presents a high performance multicore platform for EEG based seizure detection and analysis. This platform performs continuous multichannel detection and analysis of seizures for epilepsy patients. The detection unit will detect the seizures based on feature extraction process once the seizure detection is done enables the analysis circuit that process the data based Uridva Triyabhakyam based 128 point FFT and transmits energy and frequency contents of EEG data. All proposed blocks are simulated and synthesized using Xilinx ISE and coding is done in Verilog.

The Electrical Analogue Computer of Microtubule’s Protofilament

Microtubules as essential biopolymers implicated into electrical intracellular transport open a lot of questions about their intrinsic character of dynamic instability. Both experimental and theoretical investigations are used to understand their behavior in order to mimic and build powerful and smart biomaterials. So, in this paper, by analytical and computational approaches, we proposed an electrical analogue computer of microtubule’s protofilament drawing from the partial differential equation which describes microtubule’s motion. Using the computing elements, namely, operational amplifiers, capacitors, and resistors, we designed analytically the bioelectronic circuit of the microtubule’s protofilament. To validate our model, Runge–Kutta code was used to solve the partial differential equation of MT’s motion on software Matlab, and then, the results obtained are used as a controller to fit and validate numerical results obtained by running the bioelectronic circuit on software PSpice. It is shown that the analogue circuit displayed spontaneous electrical activity consistent with self-sustained electrical oscillations. We found out that two behaviors were exhibited by the voltage generated from the electrical analogue computer of MT’s protofilament; amplification and damping behaviors are modulated by the values of the resistor of the summing operational amplifier. From our study, it is shown that low values of the resistor promote damping behavior while high values of the resistor promote an amplification behavior. So microtubule’s protofilament exhibits different spontaneous regimes leading to different oscillatory modes. This study put forward the possibility to build microtubule’s protofilament as a biotransistor.

Autonomous initiation of pacemaking by L-type Cav1.3 calcium channels in mouse sino-atrial myocytes

Cardiac pacemaking relies on the spontaneous electrical activity in the right atrium of sino-atrial myocytes (SANCs). Automaticity in SANCs results from a robust interplay of membrane ion channels activity and intracellular calcium dynamics. However, only a fraction of isolated SANCs exhibit rhythmic firing, whereas most SANCs show irregular (dysrhythmic) firing or remain dormant. To study the capability of L-type Cav1.3 calcium channels to initiate automaticity in dormant SANCs under β-adrenergic stimulation we used a knock-in mouse strain in which the sensitivity of Cav1.2 α1 subunits to dihydropyridines (DHP) was inactivated (Cav1.2DHP-/-). We performed current-clamp recordings on isolated SANCs under isoprenaline (ISO, 100 nM) and in the absence or presence of the DHP blocker Nifedipine (Nife, 3 μM). In rhythmic SANCs, Nife significantly reduced the spontaneous firing under ISO perfusion (ISO: 447 ± 12, ISO + Nife: 233 ± 25 bpm). In dysrhythmic SANCs, Nife significantly reduced the spontaneous rate under ISO in 60% of the cells (ISO: 386 ± 12, ISO + Nife: 188 ± 47 bpm) and completely stopped it in 40% (295 ± 29 bpm to 0). On 25 dormant SANCs, 50% started firing after ISO perfusion (0 to 320 ± 46 bpm). Strikingly, in 75% of them, Nife totally blocked this ISO-induced firing. Moreover, dormant SANCs showed a statistically significant increase in action potential (AP) threshold under ISO compared to dysrhythmic and rhythmic SANCs (dormant: −30.1 ± 2.5, dysrhythmic: −43.3 ± 2.3, rhythmic: −41.2 ± 2.1 mV). No significant difference was observed in the other AP parameters between dormant, dysrhythmic and rhythmic SANCs under ISO. Our results indicate that Cav1.3 channels can generate pacemaker activity autonomously, at least in a particular subpopulation of SANCs, while it is responsible of about half of the automaticity in the others.

An efficient neuron-astrocyte differentiation protocol from human embryonic stem cell-derived neural progenitors to assess chemical-induced developmental neurotoxicity

Human embryonic stem cell neuronal differentiation models provide promising in vitro tools for the prediction of developmental neurotoxicity of chemicals. Such models mimic essential elements of human relevant neuronal development, including the differentiation of a variety of brain cell types and their neuronal network formation as evidenced by specific gene and protein biomarkers. However, the reproducibility and lengthy culture duration of cell models present drawbacks and delay regulatory implementation. Here we present a relatively short and robust protocol to differentiate H9-derived neural progenitor cells (NPCs) into a neuron-astrocyte co-culture. When frozen-stored NPCs were re-cultured and induced into neuron-astrocyte differentiation, they showed gene- and protein expression typical for these cells, and most notably they exhibited spontaneous electrical activity within three days of culture as measured by a multi-well micro-electrode array. Modulating the ratio of astrocytes and neurons through different growth factors including glial cell line-derived neurotrophic factor (GDNF), brain-derived neurotrophic factor (BDNF), and ciliary neurotrophic factor (CNTF) did not compromise the ability to develop spontaneous electrical activity. This robust neuronal differentiation model may serve as a functional component of a testing strategy for unravelling mechanisms of developmental neurotoxicity.

An integrated 3D fluidic device with bubble guidance mechanism for long-term primary and secondary cell recordings on multi-electrode array platform

A 3D fluidic device (3D-FD) is designed and developed with the capability of auto bubble guidance via a helical pathway in a 3D geometry. This assembly is integrated to a multi-electrode array (MEA) to maintain secondary cell lines, primary cells and primary retinal tissue explants of chick embryos for continuous monitoring of the growth and electrophysiology recording. The ability to maintain the retinal tissue explant, extracted from day 14 (E-14) and day 21 (E-21) chick embryos in an integrated 3D-FD MEA for long duration (>100 h) and study the development is demonstrated. The enhanced duration of monitoring offered by this device is due to the controlled laminar flow and the maintenance of a stable microenvironment. The spontaneous electrical activity of the retina, including the spike recordings from the retinal ganglion layer, was monitored over a long duration. Specifically, the spiking activity in embryonic chick retinas of different days (E-14 to 21) is studied, and the presence of light-stimulated firings along with a distinct electroretinogram for E-21 mature retina provides the evidence of a stable microenvironment over a sustained period.

Propagation of spontaneous electrical activity in the ex vivo human uterus

Contractions of the non-pregnant uterus play a key role in fertility. Yet, the electrophysiology underlying these contractions is poorly understood. In this paper, we investigate the presence of uterine electrical activity and characterize its propagation in unstimulated ex vivo human uteri. Multichannel electrohysterographic measurements were performed in five freshly resected human uteri starting immediately after hysterectomy. Using an electrode grid externally and an electrode array internally, measurements were performed up to 24 h after hysterectomy and compared with control. Up to 2 h after hysterectomy, we measured biopotentials in all included uteri. The median root mean squared (RMS) values of the external measurements ranged between 3.95 μV (interquartile range (IQR) 2.41–14.18 μV) and 39.4 μV (interquartile range (IQR) 10.84–105.64 μV) and were all significantly higher than control (median RMS of 1.69 μV, IQR 1.13–3.11 μV), consisting of chicken breast meat. The RMS values decreased significantly over time. After 24 h, the median RMS (1.27 μV, IQR 0.86–3.04 μV) was comparable with the control (1.69 μV, IQR 1.13–3.11 μV, p = 0.125). The internal measurements showed a comparable pattern over time, but overall lower amplitude. The measured biopotentials propagated over the uterine surface, following both a plane-wave as well as an erratic pattern. No clear pacemaker location nor a preferred propagation direction could be identified. These results show that ex vivo uteri can spontaneously generate propagating biopotentials and provide novel insight contributing to improving our understanding of the electrophysiology of the human non-pregnant uterus.

Beta-nerve growth factor stimulates spontaneous electrical activity of in vitro embryonic mouse GnRH neurons through a P75 mediated-mechanism

The control of ovulation helps guarantee the success of reproduction and as such, contributes to the fitness of a species. In mammals, two types of ovulation are observed: induced and spontaneous ovulation. Recent work on camelids, that are induced ovulators, highlighted the role of a factor present in seminal plasma, beta Nerve Growth Factor (β-NGF), as the factor that triggers ovulation in a GnRH dependent manner. In the present work, we characterized alpaca β-NGF (aβ-NGF) and its 3D structure and compared it with human recombinant β-NGF (hβ-NGF). We showed that the β-NGF enriched fraction of alpaca semen and the human recombinant protein, both stimulated spontaneous electrical activity of primary GnRH neurons derived from mouse embryonic olfactory placodes. This effect was dose-dependent and mediated by p75 receptor signaling. P75 receptors were found expressed in vitro by olfactory ensheathing cells (OEC) in close association with GnRH neurons and in vivo by tanycytes in close vicinity to GnRH fibers in adult mouse. Altogether, these results suggested that β-NGF induced ovulation through an increase in GnRH secretion provoked by a glial dependent P75 mediated mechanism.

Auxiliary α2δ1 and α2δ3 Subunits of Calcium Channels Drive Excitatory and Inhibitory Neuronal Network Development.

VGCCs are multisubunit complexes that play a crucial role in neuronal signaling. Auxiliary α2δ subunits of VGCCs modulate trafficking and biophysical properties of the pore-forming α1 subunit and trigger excitatory synaptogenesis. Alterations in the expression level of α2δ subunits were implicated in several syndromes and diseases, including chronic neuropathic pain, autism, and epilepsy. However, the contribution of distinct α2δ subunits to excitatory/inhibitory imbalance and aberrant network connectivity characteristic for these pathologic conditions remains unclear. Here, we show that α2δ1 overexpression enhances spontaneous neuronal network activity in developing and mature cultures of hippocampal neurons. In contrast, overexpression, but not downregulation, of α2δ3 enhances neuronal firing in immature cultures, whereas later in development it suppresses neuronal activity. We found that α2δ1 overexpression increases excitatory synaptic density and selectively enhances presynaptic glutamate release, which is impaired on α2δ1 knockdown. Overexpression of α2δ3 increases the excitatory synaptic density as well but also facilitates spontaneous GABA release and triggers an increase in the density of inhibitory synapses, which is accompanied by enhanced axonaloutgrowth in immature interneurons. Together, our findings demonstrate that α2δ1 and α2δ3 subunits play distinct but complementary roles in driving formation of structural and functional network connectivity during early development. An alteration in α2δ surface expression during critical developmental windows can therefore play a causal role and have a profound impact on the excitatory-to-inhibitory balance and network connectivity.SIGNIFICANCE STATEMENT The computational capacity of neuronal networks is determined by their connectivity. Chemical synapses are the main interface for transfer of information between individual neurons. The initial formation of network connectivity requires spontaneous electrical activity and the calcium channel-mediated signaling. We found that, in early development, auxiliary α2δ3 subunits of calcium channels foster presynaptic release of GABA, trigger formation of inhibitory synapses, and promote axonal outgrowth in inhibitory interneurons. In contrast, later in development, α2δ1 subunits promote the glutamatergic neurotransmission and synaptogenesis, as well as strongly enhance neuronal network activity. We propose that formation of connectivity in neuronal networks is associated with a concerted interplay of α2δ1 and α2δ3 subunits of calcium channels.

On the validation of the Newcomb[formula omitted]Benford Law and the Weibull distribution in neuromuscular transmission

The neuromuscular junction represents a relevant substrate for revealing important biophysical mechanisms of synaptic transmission. In this context, calcium ions are important in the synapse machinery, providing the nerve impulse transmission to the muscle fiber. In this work, we carefully investigated whether intervals of spontaneous electrical activity, recorded in seven different calcium concentrations, conform to the Newcomb-Benford Law. Our analysis revealed that electrical discharge of neuromuscular junction yields the expected values for Newcomb-Benford Law for first and second digits, for different calcium concentrations. On the other hand, first-two digits archived conformity especially for concentrations much above the physiological level. We next examined previous theoretical studies, establishing a relation between the law and lognormal and Weibull distributions. We showed that the Weibull distribution is more appropriate to fit the intervals as compared to the lognormal distribution. Altogether, the present findings strongly suggest that the electrical discharge dynamics is characterized by base-invariance and scale-invariance, being the time intervals also well described by Weibull statistics.