Electrical Properties Of Neurons Research Articles

High OXPHOS efficiency in RA-FUdr-differentiated SH-SY5Y cells: involvement of cAMP signalling and respiratory supercomplexes

Neurons are highly dependent on mitochondria to meet their bioenergetic needs and understanding the metabolic changes during the differentiation process is crucial in the neurodegeneration context. Several in vitro approaches have been developed to study neuronal differentiation and bioenergetic changes. The human SH-SY5Y cell line is a widely used cellular model and several differentiation protocols have been developed to induce a neuron-like phenotype including retinoic acid (RA) treatment. In this work we obtained a homogeneous functional population of neuron-like cells by a two-step differentiation protocol in which SH-SY5Y cells were treated with RA plus the mitotic inhibitor 2-deoxy-5-fluorouridine (FUdr). RA-FUdr treatment induced a neuronal phenotype characterized by increased expression of neuronal markers and electrical properties specific to excitable cells. In addition, the RA-FUdr differentiated cells showed an enrichment of long chain and unsaturated fatty acids (FA) in the acyl chain composition of cardiolipin (CL) and the bioenergetic analysis evidences a high coupled and maximal respiration associated with high mitochondrial ATP levels. Our results suggest that the observed high oxidative phosphorylation (OXPHOS) capacity may be related to the activation of the cyclic adenosine monophosphate (cAMP) pathway and the assembly of respiratory supercomplexes (SCs), highlighting the change in mitochondrial phenotype during neuronal differentiation.

Role of Electromagnetic Activity in Cellular Mechanics

The cell is the building block of life since it is the fundamental unit of all living things. Organelles, the cytoplasm, the nucleus, and other structures all have specific roles in cells. Genetic makeup, which controls cell growth, reproduction, and environmental response, determines the structure and function of cells. It is commonly known that cells communicate chemically and electrically. Cellular interactions via other physical fields are exactly the opposite. The electromagnetic field (EMF) is the most likely option for a different type of cellular interaction. This review delves into the role of electromagnetic fields in cells and their consequential impact on cell behavior. This gives a broad perspective on the basic construction and operation of cells, presents the notion of cellular mechanics, and deepens the understanding of the pivotal function of microtubules and centrosomes in cellular division. It also explores their interplay with the electromagnetic field. The discussion extends to how EMF influences ion channels on the cell membrane, a critical component in cellular communication, and the electrical properties of neurons. This review concludes by identifying the current limitations and gaps in EMF research in cells, such as constraints in experimental methods and technology, and the need for more comprehensive theories and models to fully understand these complex processes.

Myelination dictates axonal viscoelasticity.

During development, dramatic changes in myelination, growth of neural networks and changes in grey-to-white matter ratio build up the astonishingly plastic brain of a child. The progressive increase in myelination insulates the nervous system, which, in turn, modifies the mechanical microenvironment of the brain spatiotemporally. A growing body of evidence demonstrates the role of mechanical forces in growth, differentiation, maturation and electrical properties of neurons. However, due to limitations in imaging resolution, the exact relationship between myelination, axonal organization and the mechanical properties of nerves at the cellular level is still unknown. Here, we propose a novel approach to study the direct relationship between axonal viscoelasticity with changing fibre anisotropy and myelination during development. With the use of atomic force microscopy (AFM) with in situ fluorescent imaging of the primary neuron-oligodendrocyte co-cultures, we found that as axons are progressively myelinated in vitro, their stiffness increases. Direct quantification of myelin along axons using immunofluorescence also demonstrated a positive correlation between increased myelination over time and increased axonal stiffness (p = .001). Notably, AFM measurements along a single axon showed that the Young's modulus measured across myelinated regions were significantly higher than those of adjacent unmyelinated segments at all time points (p < .0001). Force-relaxation analysis also demonstrated that myelin sheath dominates the regulation of viscoelasticity of axons temporally. Collectively, our findings indicate a direct link between myelination, axonal orientation and viscoelasticity, providing important insights about the mechanical environment in the paediatric brain, with direct implications for our understanding of developmental brain disorders and paediatric brain injury.

Effects of subtoxic 3-methylmethcathinone concentrations on neuronal cell electrical properties

Synthetic cathinones are commonly abused novel psychoactive substances (NPS) that are consumed alone or in combination with other psychoactive drugs via the oral, intranasal, or intravenous routes. These substances induce physiological and subjective effects typical of psychostimulant drugs, although with a faster onset and shorter duration when compared to amphetamine derivatives. A common consequence of their short half-lives and duration of effects, is repeated administration or bingeing that results in an increase in the number of associated deaths. New synthetic cathinones, now in the fourth generation, have increasing potency and toxicity as compared to those from previous generations. NPS may interfere with the electrical activity of the catecholaminergic neuron, causing damages to neuronal function. The aim of this research is to investigate the effects of 3-methylmethcathinone (3-MMC) on excitability of neuronal cells to identify mechanisms underlying its neurotoxicity. Functional techniques detecting neuronal electrical properties including Fura-2-video imaging and current clamp electrophysiology were applied to single neurons exposed to subtoxic 3-MMC concentrations. Changes in intracellular calcium homeostasis were correlated to neuronal electrical signals during exposure. Neuronal viability was measured in cells exposed to a large range of 3-MMC concentrations by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. This assay measures metabolic cell activity by detecting the conversion of the water-soluble yellow MTT dye to an insoluble purple formazan by active mitochondrial reductases. Formazan is solubilized and its concentration determined by optical density at 570 nm. Under conditions of neuronal toxicity, a significant change in metabolic activity is identified enabling detection of cell stress from exposure to a toxic agent. 3-MMC did not affect neuronal viability at 10–300 nM concentrations. Time-lapse experiments measuring intracellular calcium concentrations ([Ca2+]i) after membrane depolarization showed that 3-MMC prevented [Ca2+]i increases elicited by high K+. At the same time current-clamp experiments revealed that 3-MMC shifts membrane potential to more depolarized values at the same range of concentrations. Collectively, before inducing neurotoxicity, 3-MMC may interfere with the electrical properties of neuronal plasma membranes, thus, dysregulating [Ca2+]i homeostasis. 3-MMC interfered with membrane depolarization at subtoxic concentrations, suggesting the ability of this synthetic cathinone to modulate an as yet unknown voltage-dependent channel(s) at the neuronal level. Due to the lack of knowledge about mechanisms underlying 3-MMC neurotoxicity, investigation of putative targets may be useful for the treatment and/or prevention of its toxic effects in humans.

An excitable systems framework for control of cells

Excitable systems, with their characteristic fast positive feedback and delayed negative feedback, have fascinating dynamical properties such as repeated bursts that can couple in space to form waves and oscillations. While the excitable systems character of neuronal electrical properties is well established, recent research has demonstrated that signaling pathways and biomechanical systems of cells are also excitable systems with internal biochemical waves and oscillations especially of actin polymerization.

Bidirectional Modulation of Neuronal Cells Electrical and Mechanical Properties Through Pristine and Functionalized Graphene Substrates.

In recent years, the quest for surface modifications to promote neuronal cell interfacing and modulation has risen. This course is justified by the requirements of emerging technological and medical approaches attempting to effectively interact with central nervous system cells, as in the case of brain-machine interfaces or neuroprosthetic. In that regard, the remarkable cytocompatibility and ease of chemical functionalization characterizing surface-immobilized graphene-based nanomaterials (GBNs) make them increasingly appealing for these purposes. Here, we compared the (morpho)mechanical and functional adaptation of rat primary hippocampal neurons when interfaced with surfaces covered with pristine single-layer graphene (pSLG) and phenylacetic acid-functionalized single-layer graphene (fSLG). Our results confirmed the intrinsic ability of glass-supported single-layer graphene to boost neuronal activity highlighting, conversely, the downturn inducible by the surface insertion of phenylacetic acid moieties. fSLG-interfaced neurons showed a significant reduction in spontaneous postsynaptic currents (PSCs), coupled to reduced cell stiffness and altered focal adhesion organization compared to control samples. Overall, we have here demonstrated that graphene substrates, both pristine and functionalized, could be alternatively used to intrinsically promote or depress neuronal activity in primary hippocampal cultures.

Effects of electromagnetic fields on neuronal ion channels: a systematic review.

Many aspects of chemistry and biology are mediated by electromagnetic field (EMF) interactions. The central nervous system (CNS) is particularly sensitive to EMF stimuli. Studies have explored the direct effect of different EMFs on the electrical properties of neurons in the last two decades, particularly focusing on the role of voltage-gated ion channels (VGCs). This work aims to systematically review published evidence in the last two decades detailing the effects of EMFs on neuronal ion channels as per the PRISM guidelines. Following a predetermined exclusion and inclusion criteria, 22 papers were included after searches on three online databases. Changes in calcium homeostasis, attributable to the voltage-gated calcium channels, were found to be the most commonly reported result of EMF exposure. EMF effects on the neuronal landscape appear to be diverse and greatly dependent on parameters, such as the field's frequency, exposure time, and intrinsic properties of the irradiated tissue, such as the expression of VGCs. Here, we systematically clarify how neuronal ion channels are particularly affected and differentially modulated by EMFs at multiple levels, such as gating dynamics, ion conductance, concentration in the membrane, and gene and protein expression. Ion channels represent a major transducer for EMF-related effects on the CNS.

Aromatic l-amino acid decarboxylase deficiency: a patient-derived neuronal model for precision therapies.

Aromatic l-amino acid decarboxylase (AADC) deficiency is a complex inherited neurological disorder of monoamine synthesis which results in dopamine and serotonin deficiency. The majority of affected individuals have variable, though often severe cognitive and motor delay, with a complex movement disorder and high risk of premature mortality. For most, standard pharmacological treatment provides only limited clinical benefit. Promising gene therapy approaches are emerging, though may not be either suitable or easily accessible for all patients. To characterize the underlying disease pathophysiology and guide precision therapies, we generated a patient-derived midbrain dopaminergic neuronal model of AADC deficiency from induced pluripotent stem cells. The neuronal model recapitulates key disease features, including absent AADC enzyme activity and dysregulated dopamine metabolism. We observed developmental defects affecting synaptic maturation and neuronal electrical properties, which were improved by lentiviral gene therapy. Bioinformatic and biochemical analyses on recombinant AADC predicted that the activity of one variant could be improved by l-3,4-dihydroxyphenylalanine (l-DOPA) administration; this hypothesis was corroborated in the patient-derived neuronal model, where l-DOPA treatment leads to amelioration of dopamine metabolites. Our study has shown that patient-derived disease modelling provides further insight into the neurodevelopmental sequelae of AADC deficiency, as well as a robust platform to investigate and develop personalized therapeutic approaches.

KATP and TRPM2-like channels couple metabolic status to resting membrane potential of octopus neurons in the mouse ventral cochlear nucleus

ATP-sensitive potassium (KATP) channels and transient receptor potential melastatin 2 (TRPM2) channels are commonly expressed both pre- and postsynaptically in the central nervous system (CNS). We hypothesized that KATP and TRPM2 may couple metabolic status to the resting membrane potential of octopus neurons of the mouse ventral cochlear nucleus (VCN).Therefore, we studied the expression of KATP channels and TRPM2 channels in octopus cells by immunohistochemical techniques and their contribution to neuronal electrical properties by the electrophysiological patch clamp technique.In immunohistochemical staining of octopus cells, labelling with Kir6.2 and SUR1 antibodies was strong, and labelling with the SUR2 antibody was moderate, but labelling with Kir6.1 was very weak. Octopus cells had intense staining with TRPM2 antibodies.In patch clamp recordings, bath application of KATP channel agonists H2O2 (880 μM), ATZ (1 mM), cromakalim (50 μM), diazoxide (200 μM), NNC 55-0118 and NN 414 separately resulted in hyperpolarizations of resting potential to different extents. Application of 8-Bro-cADPR (50 μM), a specific antagonist of TRPM2 channels, in the presence of H2O2 (880 μM) resulted in further hyperpolarization by approximately 1 mV. The amplitudes of H2O2-induced outward KATP currents and ADPR-induced inward currents were 206.1 ± 31.5 pA (n = 4) and 136.8 ± 22.4 pA, respectively, at rest. Their respective reversal potentials were -77 ± 2.6 mV (n = 3) and -6.3 ± 2.9 (n = 3) and -6.3 ± 2.9 (n = 3).In conclusion, octopus cells appear to possess both KATP channels and TRPM2-like channels. KATP might largely be constituted by SUR1–Kir6.2 subunits and SUR2–Kir6.2 subunits. Both KATP and TRPM2-like channels might have a modulatory action in setting the membrane potential.

Transcranial Focused Ultrasound Modulates Electrical Behavior of the Neurons: Design and Implementation of a Model.

Background: Recently, ultrasonic neuromodulation research has been an important and interesting issue. Ultrasonic neuromodulation is possible by the use of low-intensity transcranial focused ultrasound (tFUS) to stimulate or inhibit the neural structures. The primary capability of this method is the improvement in the treatment progress of certain neurological and psychiatric disorders noninvasively. tFUS is able to modulate ionic currents and neural depolarization, causing the alteration in electrical properties of neuronsObjective: The study aims to investigate the effect of tFUS waves on the electrical behavior of neurons using the simulation methodMaterial and Methods: In the first part of this simulation study, the propagation of tFUS waves throughout the head was simulated to calculate the value of acoustic pressure at the cortex. In the second part, cortical neurons were simulated by a simple model of spiking neurons proposed by Izhikevich for three common dynamics. Then, the capacitance model was proposed to determine the alteration in the electrical behavior of the neurons during tFUS stimulation.Results: At the resting state, the electric potential of the neuron’s membrane through the tFUS stimulation has an amplitude of about 30 mv with the similar oscillatory behavior of the acoustic waveform; while,the ultimate electrical behavior of the neuron’s membrane indicates a decrease in the electric potential when the neurons fireConclusion: The electrical behavior of the neuron and the range of its membrane voltage modulated during ultrasonic stimulation. The reduction in the amplitude of membrane potential was observed while neuron spikes

Modulation of the intrinsic neuronal excitability by multifunctional liposomes tailored for the treatment of Alzheimer's disease.

PurposeNanotechnologies turned out to be promising in the development of diagnostic and therapeutic approaches toward neurodegenerative disorders. However, only a very scant number of nanodevices until now proved to be effective on preclinical animal models. Although specific tests in vivo are available to assess the potential toxicity of these nanodevices on cognitive functions, those to evaluate their biosafety in vitro on neurons are still to be improved.Materials and methodsWe utilized the patch-clamp technique on primary cultures of cortical neural cells isolated from neonatal rats, aiming to evaluate their electrical properties after the incubation with liposomes (mApoE-PA-LIPs), previously proved able to cross the blood–brain barrier and to be effective on mouse models of Alzheimer’s disease (AD), both in the absence and in the presence of β-amyloid peptide oligomers.ResultsData show a high degree of biocompatibility, evaluated by lactate dehydrogenase (LDH) release and MTT assay, and the lack of cellular internalization. After the incubation with mApoE-PA-LIPs, neuronal membranes show an increase in the input resistance (from 724.14±76 MΩ in untreated population to 886.06±86 MΩ in the treated one), a reduction in the rheobase current (from 29.6±3 to 24.2±3 pA in untreated and treated, respectively), and an increase of the firing frequency, consistent with an ultimate increase in intrinsic excitability. Data obtained after co-incubation of mApoE-PA-LIPs with β-amyloid peptide oligomers suggest a retention of liposome efficacy.ConclusionThese data suggest the ability of liposomes to modulate neuronal electrical properties and are compatible with the previously demonstrated amelioration of cognitive functions induced by treatment of AD mice with liposomes. We conclude that this electrophysiological approach could represent a useful tool for nanomedicine to evaluate the effect of nanoparticles on intrinsic neuronal excitability.

Shank3-deficient thalamocortical neurons show HCN channelopathy and alterations in intrinsic electrical properties.

Shank3 increases the HCN channel surface expression in heterologous expression systems. Shank3Δ13-16 deficiency causes significant reduction in HCN2 expression and Ih current amplitude in thalamocortical (TC) neurons. Shank3Δ13-16 - but not Shank3Δ4-9 -deficient TC neurons share changes in basic electrical properties which are comparable to those of HCN2-/- TC neurons. HCN channelopathy may critically mediate events downstream from Shank3 deficiency. SHANK3 is a scaffolding protein that is highly enriched in excitatory synapses. Mutations in the SHANK3 gene have been linked to neuropsychiatric disorders especially the autism spectrum disorders. SHANK3 deficiency is known to cause impairments in synaptic transmission, but its effects on basic neuronal electrical properties that are more localized to the soma and proximal dendrites remain unclear. Here we confirmed that in heterologous expression systems two different mouse Shank3 isoforms, Shank3A and Shank3C, significantly increase the surface expression of the mouse hyperpolarization-activated, cyclic-nucleotide-gated (HCN) channel. In Shank3Δ13-16 knockout mice, which lack exons 13-16 in the Shank3 gene (both Shank3A and Shank3C are removed) and display a severe behavioural phenotype, the expression of HCN2 is reduced to an undetectable level. The thalamocortical (TC) neurons from the ventrobasal (VB) complex of Shank3Δ13-16 mice demonstrate reduced Ih current amplitude and correspondingly increased input resistance, negatively shifted resting membrane potential, and abnormal spike firing in both tonic and burst modes. Impressively, these changes closely resemble those of HCN2-/- TC neurons but not of the TC neurons from Shank3Δ4-9 mice, which lack exons 4-9 in the Shank3 gene (Shank3C still exists) and demonstrate moderate behavioural phenotypes. Additionally, Shank3 deficiency increases the ratio of excitatory/inhibitory balance in VB neurons but has a limited impact on the electrical properties of connected thalamic reticular (RTN) neurons. These results provide new understanding about the role of HCN channelopathy in mediating detrimental effects downstream from Shank3 deficiency.

Spatial resolution of electrical source localization depends on inter-electrode spacing and signal-to-noise ratio

Abstract Extracellular recordings of electrical neuronal sources with non-planar multichannel microelectrodes promise a high spatio-temporal resolution. We have developed signal-based algorithms, simulations and models to inversely estimate neuronal source positions and electrical properties by using multi-sensor recorded extracellular action potentials (EAP). Here, we analyse the dependence of electrode configurations on the position estimation by simulations. Estimations were simulated for various inter-electrode spacings, electrode-source distances and signal-to-noise ratios. The results show that inverse estimation depends on the electrode size or rather on the inter-electrode spacing. We find, as a rule, the larger the spacing, the larger the eligible source location area, but estimation quality of sources which are in the proximity of an electrode contact decreases. In addition, noise worsen the estimation and decreases the assessable distance between source and electrode. Thus, multichannel micro-electrodes should be selected towards signal and spatial sensitivity requirements.

Neural hyperactivity in the amygdala induced by chronic treatment of rats with analgesics may elucidate the mechanisms underlying psychiatric comorbidities associated with medication-overuse headache

BackgroundPatients with medication-overuse headache suffer not only from chronic headache, but often from psychiatric comorbidities, such as anxiety and depression. The mechanisms underlying these comorbidities are unclear, but the amygdala is likely to be involved in their pathogenesis. To investigate the mechanisms underlying the comorbidities we used elevated plus maze and open field tests to assess anxiety-like behavior in rats chronically treated with analgesics. We measured the electrical properties of neurons in the amygdala, and examined the cortical spreading depression (CSD)-evoked expression of Fos in the trigeminal nucleus caudalis (TNC) and amygdala of rats chronically treated with analgesics. CSD, an analog of aura, evokes Fos expression in the TNC of rodents suggesting trigeminal nociception, considered to be a model of migraine.ResultsIncreased anxiety-like behavior was seen both in elevated plus maze and open field tests in a model of medication overuse produced in male rats by chronic treatment with aspirin or acetaminophen. The time spent in the open arms of the maze by aspirin- or acetaminophen-treated rats (53 ± 36.1 and 37 ± 29.5 s, respectively) was significantly shorter than that spent by saline-treated vehicle control rats (138 ± 22.6 s, P < 0.001). Chronic treatment with the analgesics increased the excitability of neurons in the central nucleus of the amygdala as indicated by their more negative threshold for action potential generation (–54.6 ± 5.01 mV for aspirin-treated, –55.2 ± 0.97 mV for acetaminophen-treated, and –31.50 ± 5.34 mV for saline-treated rats, P < 0.001). Chronic treatment with analgesics increased the CSD-evoked expression of Fos in the TNC and amygdala [18 ± 10.2 Fos-immunoreactive (IR) neurons per slide in the amygdala of rats treated with aspirin, 11 ± 5.4 IR neurons per slide in rats treated with acetaminophen, and 4 ± 3.7 IR neurons per slide in saline-treated control rats, P < 0.001].ConclusionsChronic treatment with analgesics can increase the excitability of neurons in the amygdala, which could underlie the anxiety seen in patients with medication-overuse headache.

Obtaining Multi-electrode Array Recordings from Human Induced Pluripotent Stem Cell-Derived Neurons.

Neuronal electrical properties are often aberrant in neurological disorders. Human induced pluripotent stem cells (hiPSCs)-derived neurons represent a useful platform for neurological disease modeling, drug discovery and toxicity screening in vitro. Multi-electrode array (MEA) systems offer a non-invasive and label-free platform to record neuronal evoked-responses concurrently from multiple electrodes. To better detect the neural network changes, we used the Axion Maestro MEA platform to assess neuronal activity and bursting behaviors in hiPSC-derived neuronal cultures. Here we describe the detailed protocol for neuronal culture preparation, MEA recording, and data analysis, which we hope will benefit other researchers in the field.

No Evidence for Sex Differences in the Electrophysiological Properties and Excitatory Synaptic Input onto Nucleus Accumbens Shell Medium Spiny Neurons

Sex differences exist in how the brain regulates motivated behavior and reward, both in normal and pathological contexts. Investigations into the underlying neural mechanisms have targeted the striatal brain regions, including the dorsal striatum and nucleus accumbens core and shell. These investigations yield accumulating evidence of sexually different electrophysiological properties, excitatory synaptic input, and sensitivity to neuromodulator/hormone action in select striatal regions both before and after puberty. It is unknown whether the electrical properties of neurons in the nucleus accumbens shell differ by sex, and whether sex differences in excitatory synaptic input are present before puberty. To test the hypothesis that these properties differ by sex, we performed whole-cell patch-clamp recordings on male and female medium spiny neurons (MSNs) in acute brain slices obtained from prepubertal rat nucleus accumbens shell. We analyzed passive and active electrophysiological properties, and miniature EPSCs (mEPSCs). No sex differences were detected; this includes those properties, such as intrinsic excitability, action potential afterhyperpolarization, threshold, and mEPSC frequency, that have been found to differ by sex in other striatal regions and/or developmental periods. These findings indicate that, unlike other striatal brain regions, the electrophysiological properties of nucleus accumbens shell MSNs do not differ by sex. Overall, it appears that sex differences in striatal function, including motivated behavior and reward, are likely mediated by other factors and striatal regions.

Multi-walled carbon nanotubes change morpho-functional and GABA characteristics of mouse cortical astrocytes

BackgroundMulti-walled carbon nanotubes (MW-CNTs) have been extensively explored for their possible beneficial use in the nervous system. CNTs have shown to modulate neuronal growth and electrical properties, but its effect that varying length of MW-CNTs on primary astrocyte roles have not been clearly demonstrated yet.ResultsWe investigate here the effect of MW-CNTs on astrocytic morphology, cell–cell interaction and the distribution of intracellular GABA (gamma-amino butyric acid). Primary cultured cortical astrocytes on MW-CNT-coated glass coverslips grow rounder and make more cell–cell interactions, with many cell processes, compared to astrocytes on poly-d-lysine (PDL) coverslips. In addition, intracellular GABA spreads into the cell processes of astrocytes on MW-CNT coverslips. When this GABA spreads into cell processes from the cell body GABA can be released more easily and in larger quantities compared to astrocytes on PDL coverslips.ConclusionsOur result confirm that MW-CNTs modulate astrocytic morphology, the distribution of astrocytic GABA, cell–cell interactions and the extension of cell processes. CNTs look to be a promising material for use neuroprosthetics such as brain-machine interface technologies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12951-015-0152-y) contains supplementary material, which is available to authorized users.

AMIGO-Kv2.1 Potassium Channel Complex Is Associated With Schizophrenia-Related Phenotypes.

The enormous variability in electrical properties of neurons is largely affected by a multitude of potassium channel subunits. Kv2.1 is a widely expressed voltage-dependent potassium channel and an important regulator of neuronal excitability. The Kv2.1 auxiliary subunit AMIGO constitutes an integral part of the Kv2.1 channel complex in brain and regulates the activity of the channel. AMIGO and Kv2.1 localize to the distinct somatodendritic clusters at the neuronal plasma membrane. Here we have created and characterized a mouse line lacking the AMIGO gene. Absence of AMIGO clearly reduced the amount of the Kv2.1 channel protein in mouse brain and altered the electrophysiological properties of neurons. These changes were accompanied by behavioral and pharmacological abnormalities reminiscent of those identified in schizophrenia. Concomitantly, we have detected an association of a rare, population-specific polymorphism of KV2.1 (KCNB1) with human schizophrenia in a genetic isolate enriched with schizophrenia. Our study demonstrates the involvement of AMIGO-Kv2.1 channel complex in schizophrenia-related behavioral domains in mice and identifies KV2.1 (KCNB1) as a strong susceptibility gene for schizophrenia spectrum disorders in humans.

Oxytocin-induced membrane hyperpolarization in pain-sensitive dorsal root ganglia neurons mediated by Ca2+/nNOS/NO/KATP pathway

Oxytocin (OT) plays an important role in pain modulation and antinociception in the central nervous system. However, little is known about its peripheral effects. This study was conducted to investigate the effect of OT on the electrical properties of neurons in the dorsal root ganglia (DRG) and the underlying mechanisms. DRG neurons from adult rats were acutely dissociated and cultured. Intracellular Ca2+ was determined by fluorescent microscopy using an indicator dye. The electrical properties of DRG neurons were tested by patch-clamp recording. The oxytocin receptor (OTR) and neuronal nitric oxide synthase (nNOS) on DRG neurons were assessed with immunofluorescence assays. OTR co-localized with nNOS in most of Isolectin B4 (IB4)-binding cultured DRG neurons in rats. OT decreased the excitability, increased the outward current, and evoked the membrane hyperpolarization in cultured DRG neurons. Sodium nitroprusside (SNP), the donor of nitric oxide (NO), exerted similar effects as OT on the membrane potential of cultured DRG neurons. OT increased the production of NO in DRGs and cultured DRG neurons. Pre-treatment of the OTR antagonist atosiban or the selective nNOS inhibitor N-Propyl-l-arginine (NPLA) significantly attenuated the hyperpolarization effect evoked by OT. OT produced a concentration-dependent increase in intracellular Ca2+ in DRG neurons that responds to capsaicin, which can be attenuated by atosiban, but not by NPLA. OT-evoked membrane hyperpolarization and increase of outward current were distinctly attenuated by glibenclamide, a blocker of ATP-sensitive K+ (KATP) channel. OT might be an endogenous antinociceptive agent and the peripheral antinociceptive effects of OT are mediated by activation of the Ca2+/nNOS/NO/KATP pathway in DRG neurons.

Selective Inactivation of Striatal FosB/ΔFosB-Expressing Neurons Alleviates L-DOPA–Induced Dyskinesia

BackgroundΔFosB is a surrogate marker of L-DOPA–induced dyskinesia (LID), the unavoidable disabling consequence of Parkinson’s disease L-DOPA long-term treatment. However, the relationship between the electrical activity of FosB/ΔFosB-expressing neurons and LID manifestation is unknown. MethodsWe used the Daun02 prodrug-inactivation method associated with lentiviral expression of β-galactosidase under the control of the FosB promoter to investigate a causal link between the activity of FosB/ΔFosB-expressing neurons and dyskinesia severity in both rat and monkey models of Parkinson’s disease and LID. Whole-cell recordings of medium spiny neurons (MSNs) were performed to assess the effects of Daun02 and daunorubicin on neuronal excitability. ResultsWe first show that daunorubicin, the active product of Daun02 metabolism by β-galactosidase, decreases the activity of MSNs in rat brain slices and that Daun02 strongly decreases the excitability of rat MSN primary cultures expressing β-galactosidase upon D1 dopamine receptor stimulation. We then demonstrate that the selective, and reversible, inhibition of FosB/ΔFosB-expressing striatal neurons with Daun02 decreases the severity of LID while improving the beneficial effect of L-DOPA. ConclusionsThese results establish that FosB/ΔFosB accumulation ultimately results in altered neuronal electrical properties sustaining maladaptive circuits leading not only to LID but also to a blunted response to L-DOPA. These findings further reveal that targeting dyskinesia can be achieved without reducing the antiparkinsonian properties of L-DOPA when specifically inhibiting FosB/ΔFosB-accumulating neurons.