scholarly journals Non-synaptic Cell-Autonomous Mechanisms Underlie Neuronal Hyperactivity in a Genetic Model of PIK3CA-Driven Intractable Epilepsy

2021 ◽  
Vol 14 ◽  
Author(s):  
Achira Roy ◽  
Victor Z. Han ◽  
Angela M. Bard ◽  
Devin T. Wehle ◽  
Stephen E. P. Smith ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Genetic Model ◽  
Ex Vivo ◽  
Significant Proportion ◽  
Intractable Epilepsy ◽  
Therapeutic Interventions ◽  
Hippocampal Pyramidal Neurons ◽  
Phosphoinositide 3 Kinase

Patients harboring mutations in the PI3K-AKT-MTOR pathway-encoding genes often develop a spectrum of neurodevelopmental disorders including epilepsy. A significant proportion remains unresponsive to conventional anti-seizure medications. Understanding mutation-specific pathophysiology is thus critical for molecularly targeted therapies. We previously determined that mouse models expressing a patient-related activating mutation in PIK3CA, encoding the p110α catalytic subunit of phosphoinositide-3-kinase (PI3K), are epileptic and acutely treatable by PI3K inhibition, irrespective of dysmorphology. Here we report the physiological mechanisms underlying this dysregulated neuronal excitability. In vivo, we demonstrate epileptiform events in the Pik3ca mutant hippocampus. By ex vivo analyses, we show that Pik3ca-driven hyperactivation of hippocampal pyramidal neurons is mediated by changes in multiple non-synaptic, cell-intrinsic properties. Finally, we report that acute inhibition of PI3K or AKT, but not MTOR activity, suppresses the intrinsic hyperactivity of the mutant neurons. These acute mechanisms are distinct from those causing neuronal hyperactivity in other AKT-MTOR epileptic models and define parameters to facilitate the development of new molecularly rational therapeutic interventions for intractable epilepsy.

scholarly journals Suppression of PIK3CA-driven epileptiform activity by acute pathway control

2021 ◽  
Author(s):  
Achira Roy ◽  
Victor Z. Han ◽  
Angela M. Bard ◽  
Devin T. Wehle ◽  
Stephen E. P. Smith ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Epileptiform Activity ◽  
Significant Proportion ◽  
Intractable Epilepsy ◽  
Cancer Therapeutics ◽  
Physiological Mechanisms ◽  
Hippocampal Pyramidal Neurons ◽  
Anti Cancer ◽  
Activating Mutation

ABSTRACTA significant proportion of epilepsy patients is non-responsive to conventional anti-seizure medications. Many of these patients harbor causative mutations in the PI3K-AKT-MTOR signaling pathway1–5. Understanding mutation-specific pathophysiology is critical for developing molecularly targeted therapies. Here we identify physiological mechanisms underlying dysregulation of neuronal excitability and its acute attenuation in a mouse model expressing patient-related activating mutation in Pik3ca, that encodes the p110α catalytic subunit of PI3K6. We show that Pik3ca-dependent hyperexcitability in hippocampal pyramidal neurons is mediated by changes in non-synaptic, cell-intrinsic properties, involving calcium and potassium channels. Our results also suggest a potential reason behind Pik3ca-dependent epileptic intractability. Further, we report that acute inhibition of PI3K or AKT, but not MTOR, suppresses the intrinsic epileptiform nature of the mutant neurons. This study therefore represents an important advance towards repurposing anti-cancer therapeutics to treat intractable epilepsy.

scholarly journals Vasopressin acts as a synapse organizer in limbic regions by boosting PSD95 and GluA1 expression

2020 ◽  
Author(s):  
Limei Zhang ◽  
Teresa Padilla-Flores ◽  
Vito S. Hernández ◽  
Elba Campos-Lira ◽  
Mario A. Zetter ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Ex Vivo ◽  
Hippocampal Slices ◽  
Brain Slices ◽  
Synaptic Proteins ◽  
Scaffolding Protein ◽  
Synaptic Organization ◽  
Limbic Regions

AbstractHypothalamic arginine vasopressin (AVP)-containing magnocellular neurosecretory neurons (AVPMNN) emit collaterals to synaptically innervate limbic regions influencing learning, motivational behavior and fear responses. The purpose of the present work is to characterize the dynamics of expression changes of two postsynaptic density (PSD) proteins, AMPAR subunit GluA1 and PSD scaffolding protein 95 (PSD95), which are known to be key determinants for synaptic strength, in response to in vivo and ex vivo manipulations of AVPMNN neuronal activation state, or exposure to exogenous AVP, metabolites and some signaling pathway inhibitors. Both long term water deprivation in vivo, which powerfully upregulates AVPMNN activity, and exogenous APV application ex vivo in brain slices, increased GluA1 and PSD95 expression and enhanced neuronal excitability in ventral hippocampal CA1 pyramidal neurons. Involvement of PI3k signaling in AVP-dependent plasticity is suggested by blockade of both AVP-induced protein up-regulation and enhanced neuronal excitability by the PI3k blocker wortmannin in hippocampal slices. We interpret these results as part of vasopressin’s central effects on synaptic organization in limbic regions modulating the strength of a specific set of synaptic proteins in hypothalamic-limbic circuits.Supported by grantsUNAM-DGAPA-PAPIIT-IN216918 & CONACYT-CB-238744.

scholarly journals P38 Regulates Kainic Acid-Induced Seizure and Neuronal Firing via Kv4.2 Phosphorylation

2020 ◽  
Vol 21 (16) ◽  
pp. 5921
Author(s):  
Jia-hua Hu ◽  
Cole Malloy ◽  
Dax A. Hoffman
Keyword(s):  
Kainic Acid ◽  
Molecular Mechanisms ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Neuronal Firing ◽  
Dependent Manner ◽  
Membrane Excitability ◽  
Hippocampal Pyramidal Neurons ◽  
K Current

The subthreshold, transient A-type K+ current is a vital regulator of the excitability of neurons throughout the brain. In mammalian hippocampal pyramidal neurons, this current is carried primarily by ion channels comprising Kv4.2 α-subunits. These channels occupy the somatodendritic domains of these principle excitatory neurons and thus regulate membrane voltage relevant to the input–output efficacy of these cells. Owing to their robust control of membrane excitability and ubiquitous expression in the hippocampus, their dysfunction can alter network stability in a manner that manifests in recurrent seizures. Indeed, growing evidence implicates these channels in intractable epilepsies of the temporal lobe, which underscores the importance of determining the molecular mechanisms underlying their regulation and contribution to pathologies. Here, we describe the role of p38 kinase phosphorylation of a C-terminal motif in Kv4.2 in modulating hippocampal neuronal excitability and behavioral seizure strength. Using a combination of biochemical, single-cell electrophysiology, and in vivo seizure techniques, we show that kainic acid-induced seizure induces p38-mediated phosphorylation of Thr607 in Kv4.2 in a time-dependent manner. The pharmacological and genetic disruption of this process reduces neuronal excitability and dampens seizure intensity, illuminating a cellular cascade that may be targeted for therapeutic intervention to mitigate seizure intensity and progression.

scholarly journals Chronic in vivo optogenetic stimulation modulates neuronal excitability, spine morphology and Hebbian plasticity in the mouse hippocampus

2018 ◽  
Author(s):  
Thiago C. Moulin ◽  
Lyvia L. Petiz ◽  
Danielle Rayêe ◽  
Jessica Winne ◽  
Roberto G. Maia ◽  
...  
Keyword(s):  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Ex Vivo ◽  
Morphological Changes ◽  
Spine Density ◽  
Optogenetic Stimulation ◽  
Light Pulses ◽  
Ca1 Region ◽  
Hebbian Plasticity

AbstractProlonged increases in excitation can trigger cell-wide homeostatic responses in neurons, altering membrane channels, promoting morphological changes and ultimately reducing synaptic weights. However, how synaptic downscaling interacts with classical forms of Hebbian plasticity is still unclear. In this study, we investigated whether chronic optogenetic stimulation of hippocampus CA1 pyramidal neurons in freely-moving mice could (a) cause morphological changes reminiscent of homeostatic scaling, (b) modulate synaptic currents that might compensate for chronic excitation, and (c) lead to alterations in Hebbian plasticity. After 24 h of stimulation with 15-ms blue light pulses every 90 s, dendritic spine density and area were reduced in the CA1 region of mice expressing channelrhodopsin-2 (ChR2) when compared to controls. This protocol also reduced the amplitude of mEPSCs for both the AMPA and NMDA components in ex vivo slices obtained from ChR2-expressing mice immediately after the end of stimulation. Lastly, chronic stimulation impaired the induction of LTP and facilitated that of LTD in these slices. Our results indicate that neuronal responses to prolonged network excitation can modulate subsequent Hebbian plasticity in the hippocampus.

scholarly journals EANM recommendations based on systematic analysis of small animal radionuclide imaging in inflammatory musculoskeletal diseases

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Erik H. J. G. Aarntzen ◽  
Edel Noriega-Álvarez ◽  
Vera Artiko ◽  
André H. Dias ◽  
Olivier Gheysens ◽  
...  
Keyword(s):  
Molecular Imaging ◽  
Radionuclide Imaging ◽  
Musculoskeletal Diseases ◽  
Ex Vivo ◽  
Imaging Techniques ◽  
Large Body ◽  
Therapeutic Interventions ◽  
Histopathological Analysis ◽  
Complementary Value

AbstractInflammatory musculoskeletal diseases represent a group of chronic and disabling conditions that evolve from a complex interplay between genetic and environmental factors that cause perturbations in innate and adaptive immune responses. Understanding the pathogenesis of inflammatory musculoskeletal diseases is, to a large extent, derived from preclinical and basic research experiments. In vivo molecular imaging enables us to study molecular targets and to measure biochemical processes non-invasively and longitudinally, providing information on disease processes and potential therapeutic strategies, e.g. efficacy of novel therapeutic interventions, which is of complementary value next to ex vivo (post mortem) histopathological analysis and molecular assays. Remarkably, the large body of preclinical imaging studies in inflammatory musculoskeletal disease is in contrast with the limited reports on molecular imaging in clinical practice and clinical guidelines. Therefore, in this EANM-endorsed position paper, we performed a systematic review of the preclinical studies in inflammatory musculoskeletal diseases that involve radionuclide imaging, with a detailed description of the animal models used. From these reflections, we provide recommendations on what future studies in this field should encompass to facilitate a greater impact of radionuclide imaging techniques on the translation to clinical settings.

scholarly journals In vivo magnetic resonance imaging of orthotopic prostate cancer

BioTechniques ◽  
2020 ◽  
Vol 69 (1) ◽  
pp. 37-45
Author(s):  
Murali K Ravoori ◽  
Sheela Singh ◽  
Peiying Yang ◽  
Wei Wei ◽  
Huiqin Chen ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Mechanisms Of Action ◽  
Tumor Burden ◽  
Therapeutic Interventions ◽  
Resonance Imaging ◽  
Prostate Tumors ◽  
Tumor Weight ◽  
History Of ◽  
Old Mice

Methods for imaging orthotopic prostate tumors within the prostate or small tumors with extension outside the prostate are needed to more closely model human prostate tumors, which are most commonly located within the gland or may extend just through the gland. By comparing MR sequences, we found that the T2-based Dixon ‘water only’ sequence best visualized tumors within the prostate of mouse models in both young and old mice and that tumor weight derived from this sequence correlated highly with ex vivo tumor weight (r2 = 0.98, p < 0.001, n = 12). This should aid tumor detection, margin delineation and evaluation of tumor burden to enable studies including, but not limited to, evaluating the natural history of the disease, the mechanisms of action and the efficacy of therapeutic interventions.

scholarly journals A minimally invasive catheter-based ultrasound technology for therapeutic interventions in brain: initial preclinical studies

2018 ◽  
Vol 44 (2) ◽  
pp. E13 ◽  
Author(s):  
Goutam Ghoshal ◽  
Lucy Gee ◽  
Tamas Heffter ◽  
Emery Williams ◽  
Corinne Bromfield ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Minimally Invasive ◽  
Focused Ultrasound ◽  
Ex Vivo ◽  
Experimental Studies ◽  
Rodent Model ◽  
Therapeutic Interventions ◽  
Porcine Liver

OBJECTIVEMinimally invasive procedures may allow surgeons to avoid conventional open surgical procedures for certain neurological disorders. This paper describes the iterative process for development of a catheter-based ultrasound thermal therapy applicator.METHODSUsing an ultrasound applicator with an array of longitudinally stacked and angularly sectored tubular transducers within a catheter, the authors conducted experimental studies in porcine liver, in vivo and ex vivo, in order to characterize the device performance and lesion patterns. In addition, they applied the technique in a rodent model of Parkinson’s disease to investigate the feasibility of its application in brain.RESULTSThermal lesions with multiple shapes and sizes were readily achieved in porcine liver. The feasibility of catheter-based focused ultrasound in the treatment of brain conditions was demonstrated in a rodent model of Parkinson’s disease.CONCLUSIONSThe authors show proof of principle of a catheter-based ultrasound system that can create lesions with concurrent thermode-based measurements.

scholarly journals BRAFV600E expression in neural progenitors results in a hyperexcitable phenotype in neocortical pyramidal neurons

2020 ◽  
Vol 123 (6) ◽  
pp. 2449-2464
Author(s):  
Roman U. Goz ◽  
Gülcan Akgül ◽  
Joseph J. LoTurco
Keyword(s):  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Mammalian Target Of Rapamycin ◽  
Neural Progenitors ◽  
Wild Type ◽  
Neuronal Phenotype ◽  
Neuronal Progenitors ◽  
Neocortical Neurons ◽  
Distinct Cell ◽  
Phosphoinositide 3 Kinase

This study is the first to report the cell autonomous effects of BRAFV600E mutations on the intrinsic neuronal excitability. We show that BRAFV600E alters multiple electrophysiological parameters in neocortical neurons. Similar excitability changes did not occur in cells neighboring BRAFV600E-expressing neurons, after overexpression of wild-type BRAF transgenes, or after introduction of mutations affecting the mammalian target of rapamycin (mTOR) or the catalytic subunit of phosphoinositide 3-kinase (PIK3CA). We conclude that BRAFV600E causes a distinct, cell autonomous, highly excitable neuronal phenotype when introduced somatically into neocortical neuronal progenitors.

scholarly journals The antihelminthic moxidectin enhances tonic GABA currents in rodent hippocampal pyramidal neurons

2018 ◽  
Vol 119 (5) ◽  
pp. 1693-1698
Author(s):  
Jay Spampanato ◽  
Anne Gibson ◽  
F. Edward Dudek
Keyword(s):  
Central Nervous System ◽  
Nervous System ◽  
Gaba Receptors ◽  
Pyramidal Neurons ◽  
Ex Vivo ◽  
Companion Animals ◽  
Brain Slices ◽  
Dependent Manner ◽  
Hippocampal Pyramidal Neurons ◽  
Mammalian Central Nervous System

Macrocyclic lactones (MLs) are commonly used treatments for parasitic worm and insect infections in humans, livestock, and companion animals. MLs target the invertebrate glutamate-activated chloride channel that is not present in vertebrates. MLs are not entirely inert in vertebrates, though; they have been reported to have activity in heterologous expression systems consisting of ligand-gated ion channels that are present in the mammalian central nervous system (CNS). However, these compounds are typically not able to reach significant concentrations in the CNS because of the activity of the blood-brain barrier P-glycoprotein extrusion system. Despite this, these compounds are able to reach low levels in the CNS that may be useful in the design of novel “designer” ligand-receptor systems that can be used to directly investigate neuronal control of behavior in mammals and have potential for use in treating human neurological diseases. To determine whether MLs might affect neurons in intact brains, we investigated the activity of the ML moxidectin (MOX) at native GABA receptors. Specifically, we recorded tonic and phasic miniature inhibitory postsynaptic currents (mIPSCs) in ex vivo brain slices. Our data show that MOX potentiated tonic GABA currents in a dose-dependent manner but had no concomitant effects on phasic GABA currents (i.e., MOX had no effect on the amplitude, frequency, or decay kinetics of mIPSCs). These studies indicate that behavioral experiments that implement a ML-based novel ligand-receptor system should take care to control for potential effects of the ML on native tonic GABA receptors.NEW & NOTEWORTHY We have identified a novel mechanism of action in the mammalian central nervous system for the antihelminthic moxidectin, commonly prescribed to animals worldwide and currently being evaluated for use in humans. Specifically, moxidectin applied to rodent brain slices selectively enhanced the tonic GABA conductance of hippocampal pyramidal neurons.

Slow intrinsic spikes recorded in vivo in rat CA1–CA3 hippocampal pyramidal neurons

1990 ◽  
Vol 109 (3) ◽  
pp. 294-299 ◽  
Author(s):  
Angel Nuñez ◽  
Elio García-Austt ◽  
Washington Buño
Keyword(s):  
Pyramidal Neurons ◽  
Hippocampal Pyramidal Neurons
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