scholarly journals RGS7/Gβ5/R7BP complex regulates synaptic plasticity and memory by modulating hippocampal GABABR-GIRK signaling

eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Olga Ostrovskaya ◽  
Keqiang Xie ◽  
Ikuo Masuho ◽  
Ana Fajardo-Serrano ◽  
Rafael Lujan ◽  
...  
Keyword(s):  
Synaptic Plasticity ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Dynamic Range ◽  
Gabab Receptor ◽  
Girk Channels ◽  
Hippocampal Pyramidal Neurons ◽  
Inhibitory Neurotransmitter ◽  
Membrane Anchoring

In the hippocampus, the inhibitory neurotransmitter GABA shapes the activity of the output pyramidal neurons and plays important role in cognition. Most of its inhibitory effects are mediated by signaling from GABAB receptor to the G protein-gated Inwardly-rectifying K+ (GIRK) channels. Here, we show that RGS7, in cooperation with its binding partner R7BP, regulates GABABR-GIRK signaling in hippocampal pyramidal neurons. Deletion of RGS7 in mice dramatically sensitizes GIRK responses to GABAB receptor stimulation and markedly slows channel deactivation kinetics. Enhanced activity of this signaling pathway leads to decreased neuronal excitability and selective disruption of inhibitory forms of synaptic plasticity. As a result, mice lacking RGS7 exhibit deficits in learning and memory. We further report that RGS7 is selectively modulated by its membrane anchoring subunit R7BP, which sets the dynamic range of GIRK responses. Together, these results demonstrate a novel role of RGS7 in hippocampal synaptic plasticity and memory formation.

scholarly journals Dysregulation of Astrocyte–Neuronal Communication in Alzheimer’s Disease

2021 ◽  
Vol 22 (15) ◽  
pp. 7887
Author(s):  
Carmen Nanclares ◽  
Andres Mateo Baraibar ◽  
Alfonso Araque ◽  
Paulo Kofuji
Keyword(s):  
Alzheimer’S Disease ◽  
Alzheimer's Disease ◽  
Cognitive Impairment ◽  
Synaptic Plasticity ◽  
Neuronal Excitability ◽  
Active Role ◽  
Ionic Homeostasis ◽  
Neuronal Communication ◽  
Structural Support

Recent studies implicate astrocytes in Alzheimer’s disease (AD); however, their role in pathogenesis is poorly understood. Astrocytes have well-established functions in supportive functions such as extracellular ionic homeostasis, structural support, and neurovascular coupling. However, emerging research on astrocytic function in the healthy brain also indicates their role in regulating synaptic plasticity and neuronal excitability via the release of neuroactive substances named gliotransmitters. Here, we review how this “active” role of astrocytes at synapses could contribute to synaptic and neuronal network dysfunction and cognitive impairment in AD.

Dopamine Increases the Gain of the Input-Output Response of Rat Prefrontal Pyramidal Neurons

2008 ◽  
Vol 99 (6) ◽  
pp. 2985-2997 ◽  
Author(s):  
Kay Thurley ◽  
Walter Senn ◽  
Hans-Rudolf Lüscher
Keyword(s):  
Working Memory ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
D1 Receptors ◽  
Input Output ◽  
Prefrontal Cortical ◽  
Noisy Input ◽  
Relationship Of

Dopaminergic modulation of prefrontal cortical activity is known to affect cognitive functions like working memory. Little consensus on the role of dopamine modulation has been achieved, however, in part because quantities directly relating to the neuronal substrate of working memory are difficult to measure. Here we show that dopamine increases the gain of the frequency-current relationship of layer 5 pyramidal neurons in vitro in response to noisy input currents. The gain increase could be attributed to a reduction of the slow afterhyperpolarization by dopamine. Dopamine also increases neuronal excitability by shifting the input-output functions to lower inputs. The modulation of these response properties is mainly mediated by D1 receptors. Integrate-and-fire neurons were fitted to the experimentally recorded input-output functions and recurrently connected in a model network. The gain increase induced by dopamine application facilitated and stabilized persistent activity in this network. The results support the hypothesis that catecholamines increase the neuronal gain and suggest that dopamine improves working memory via gain modulation.

scholarly journals GABAB Receptor-Mediated Regulation of Dendro-Somatic Synergy in Layer 5 Pyramidal Neurons

2021 ◽  
Vol 15 ◽  
Author(s):  
Jan M. Schulz ◽  
Jim W. Kay ◽  
Josef Bischofberger ◽  
Matthew E. Larkum
Keyword(s):  
Pyramidal Neurons ◽  
Partial Information ◽  
Gabab Receptor ◽  
Fold Increase ◽  
Substantial Contribution ◽  
Transfer Resistance ◽  
Girk Channels ◽  
Synergistic Interactions ◽  
Voltage Dependent

Synergistic interactions between independent synaptic input streams may fundamentally change the action potential (AP) output. Using partial information decomposition, we demonstrate here a substantial contribution of synergy between somatic and apical dendritic inputs to the information in the AP output of L5b pyramidal neurons. Activation of dendritic GABAB receptors (GABABRs), known to decrease APs in vivo, potently decreased synergy and increased somatic control of AP output. Synergy was the result of the voltage-dependence of the transfer resistance between dendrite and soma, which showed a two-fold increase per 28.7 mV dendritic depolarization. GIRK channels activated by dendritic GABABRs decreased voltage-dependent transfer resistances and AP output. In contrast, inhibition of dendritic L-type Ca2+ channels prevented high-frequency bursts of APs, but did not affect dendro-somatic synergy. Finally, we show that NDNF-positive neurogliaform cells effectively control somatic AP via synaptic activation of dendritic GIRK channels. These results uncover a novel inhibitory mechanism that powerfully gates cellular information flow in the cortex.

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.

Memory Beyond Synaptic Plasticity: The Role of Intrinsic Neuronal Excitability

2012 ◽  
pp. 53-80 ◽  
Author(s):  
Athanasia Papoutsi ◽  
Kyriaki Sidiropoulou ◽  
Panayiota Poirazi
Keyword(s):  
Synaptic Plasticity ◽  
Neuronal Excitability

scholarly journals Is It Feasible of Prophylactic Alpha-5 GABA(A) Receptor Blockade for Preventing POCD?

2013 ◽  
Vol 3 (3) ◽  
pp. 61-62
Author(s):  
Fuzhou Wang
Keyword(s):  
Nervous System ◽  
General Anesthesia ◽  
Neuronal Excitability ◽  
Underlying Mechanism ◽  
Gamma Aminobutyric Acid ◽  
Gaba A ◽  
Inhibitory Neurotransmitter ◽  
Inhalational Anesthetics ◽  
Exploratory Data

GAMMA-AMINOBUTYRIC ACID (GABA) is the chief inhibitory neurotransmitter in the mammalian central nervous system (CNS). It plays a role in regulating neuronal excitability throughout the nervous system. Also GABA activation is considered as the basis of general anesthesia including intravenous and inhalational anesthetics. Meanwhile, cumulating evidence indicated that GABA is the underlying mechanism of post-operative cognitive dysfunction (POCD). Based on these findings, researchers are beginning to focus on GABA as the target to treat POCD, but they ignored the role of GABA in the performance of general anesthesia, especially when the blockade of GABA was given prior to surgery. It is undoubtedly risking our patients in intra-operative awareness. Our exploratory data also verified our hypothesis in which the GABA inhibition would reduce the efficacy of inhalational anesthetics.

Specific Subtypes of GABAA Receptors Mediate Phasic and Tonic Forms of Inhibition in Hippocampal Pyramidal Neurons

2006 ◽  
Vol 96 (2) ◽  
pp. 846-857 ◽  
Author(s):  
George A. Prenosil ◽  
Edith M. Schneider Gasser ◽  
Uwe Rudolph ◽  
Ruth Keist ◽  
Jean-Marc Fritschy ◽  
...  
Keyword(s):  
Pyramidal Neurons ◽  
Pyramidal Cells ◽  
Tonic Inhibition ◽  
Mammalian Brain ◽  
Triple Mutant ◽  
Α Subunit ◽  
Hippocampal Pyramidal Neurons ◽  
Inhibitory Neurotransmitter ◽  
Ca1 Area ◽  
Hippocampal Pyramidal Cells

The main inhibitory neurotransmitter in the mammalian brain, GABA, mediates multiple forms of inhibitory signals, such as fast and slow inhibitory postsynaptic currents and tonic inhibition, by activating a diverse family of ionotropic GABAA receptors (GABAARs). Here, we studied whether distinct GABAAR subtypes mediate these various forms of inhibition using as approach mice carrying a point mutation in the α-subunit rendering individual GABAAR subtypes insensitive to diazepam without altering their GABA sensitivity and expression of receptors. Whole cell patch-clamp recordings were performed in hippocampal pyramidal cells from single, double, and triple mutant mice. Comparing diazepam effects in knock-in and wild-type mice allowed determining the contribution of α1, α2, α3, and α5 subunits containing GABAARs to phasic and tonic forms of inhibition. Fast phasic currents were mediated by synaptic α2-GABAARs on the soma and by synaptic α1-GABAARs on the dendrites. No contribution of α3- or α5-GABAARs was detectable. Slow phasic currents were produced by both synaptic and perisynaptic GABAARs, judged by their strong sensitivity to blockade of GABA reuptake. In the CA1 area, but not in the subiculum, perisynaptic α5-GABAARs contributed to slow phasic currents. In the CA1 area, the diazepam-sensitive component of tonic inhibition also involved activation of α5-GABAARs and slow phasic and tonic signals shared overlapping pools of receptors. These results show that the major forms of inhibitory neurotransmission in hippocampal pyramidal cells are mediated by distinct GABAARs subtypes.

scholarly journals β3-Adrenergic receptor-dependent modulation of the medium afterhyperpolarization in rat hippocampal CA1 pyramidal neurons

2019 ◽  
Vol 121 (3) ◽  
pp. 773-784 ◽  
Author(s):  
Timothy W. Church ◽  
Jon T. Brown ◽  
Neil V. Marrion
Keyword(s):  
Action Potential ◽  
Adrenergic Receptors ◽  
Adrenergic Receptor ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Intracellular Camp ◽  
Action Potential Firing ◽  
Hippocampal Pyramidal Neurons ◽  
Potential Firing ◽  
H Channels

Action potential firing in hippocampal pyramidal neurons is regulated by generation of an afterhyperpolarization (AHP). Three phases of AHP are recognized, with the fast AHP regulating action potential firing at the onset of a burst and the medium and slow AHPs supressing action potential firing over hundreds of milliseconds and seconds, respectively. Activation of β-adrenergic receptors suppresses the slow AHP by a protein kinase A-dependent pathway. However, little is known regarding modulation of the medium AHP. Application of the selective β-adrenergic receptor agonist isoproterenol suppressed both the medium and slow AHPs evoked in rat CA1 hippocampal pyramidal neurons recorded from slices maintained in organotypic culture. Suppression of the slow AHP was mimicked by intracellular application of cAMP, with the suppression of the medium AHP by isoproterenol still being evident in cAMP-dialyzed cells. Suppression of both the medium and slow AHPs was antagonized by the β-adrenergic receptor antagonist propranolol. The effect of isoproterenol to suppress the medium AHP was mimicked by two β3-adrenergic receptor agonists, BRL37344 and SR58611A. The medium AHP was mediated by activation of small-conductance calcium-activated K+ channels and deactivation of H channels at the resting membrane potential. Suppression of the medium AHP by isoproterenol was reduced by pretreating cells with the H-channel blocker ZD7288. These data suggest that activation of β3-adrenergic receptors inhibits H channels, which suppresses the medium AHP in CA1 hippocampal neurons by utilizing a pathway that is independent of a rise in intracellular cAMP. This finding highlights a potential new target in modulating H-channel activity and thereby neuronal excitability. NEW & NOTEWORTHY The noradrenergic input into the hippocampus is involved in modulating long-term synaptic plasticity and is implicated in learning and memory. We demonstrate that activation of functional β3-adrenergic receptors suppresses the medium afterhyperpolarization in hippocampal pyramidal neurons. This finding provides an additional mechanism to increase action potential firing frequency, where neuronal excitability is likely to be crucial in cognition and memory.

scholarly journals Strychnine-sensitive glycine receptors on pyramidal neurons in layers II/III of the mouse prefrontal cortex are tonically activated

2014 ◽  
Vol 112 (5) ◽  
pp. 1169-1178 ◽  
Author(s):  
Michael C. Salling ◽  
Neil L. Harrison
Keyword(s):  
Prefrontal Cortex ◽  
Neuronal Excitability ◽  
Pyramidal Neurons ◽  
Tonic Inhibition ◽  
Dependent Manner ◽  
Glycine Receptors ◽  
Decay Kinetics ◽  
Concentration Dependent Manner ◽  
Inhibitory Neurotransmitter ◽  
Current Shift

Processing of signals within the cerebral cortex requires integration of synaptic inputs and a coordination between excitatory and inhibitory neurotransmission. In addition to the classic form of synaptic inhibition, another important mechanism that can regulate neuronal excitability is tonic inhibition via sustained activation of receptors by ambient levels of inhibitory neurotransmitter, usually GABA. The purpose of this study was to determine whether this occurs in layer II/III pyramidal neurons (PNs) in the prelimbic region of the mouse medial prefrontal cortex (mPFC). We found that these neurons respond to exogenous GABA and to the α4δ-containing GABAA receptor (GABAAR)-selective agonist gaboxadol, consistent with the presence of extrasynaptic GABAAR populations. Spontaneous and miniature synaptic currents were blocked by the GABAAR antagonist gabazine and had fast decay kinetics, consistent with typical synaptic GABAARs. Very few layer II/III neurons showed a baseline current shift in response to gabazine, but almost all showed a current shift (15–25 pA) in response to picrotoxin. In addition to being a noncompetitive antagonist at GABAARs, picrotoxin also blocks homomeric glycine receptors (GlyRs). Application of the GlyR antagonist strychnine caused a modest but consistent shift (∼15 pA) in membrane current, without affecting spontaneous synaptic events, consistent with the tonic activation of GlyRs. Further investigation showed that these neurons respond in a concentration-dependent manner to glycine and taurine. Inhibition of glycine transporter 1 (GlyT1) with sarcosine resulted in an inward current and an increase of the strychnine-sensitive current. Our data demonstrate the existence of functional GlyRs in layer II/III of the mPFC and a role for these receptors in tonic inhibition that can have an important influence on mPFC excitability and signal processing.

Gabab Receptors: Are They Missing In Action In Focal Epilepsy Research?

2021 ◽  
Vol 19 ◽  
Author(s):  
Massimo Avoli ◽  
Maxime Lévesque
Keyword(s):  
Gabab Receptor ◽  
Focal Epilepsy ◽  
Second Messengers ◽  
Gabab Receptors ◽  
Receptor Function ◽  
Inhibitory Neurotransmitter ◽  
Epilepsy Research ◽  
Missing In Action

: GABA, the key inhibitory neurotransmitter in the adult forebrain, activates pre- and postsynaptic receptors that have been categorized as GABAA, which directly open ligand-gated (or receptor-operated) ion-channels, and GABAB, which are metabotropic since they operate through second messengers. Over the last three decades, several studies have addressed the role of GABAB receptors in the pathophysiology of generalized and focal epileptic disorders. Here, we will address their involvement in focal epileptic disorders by mainly reviewing in vitro studies that have shown: (i) how either enhancing or decreasing GABAB receptor function can favour epileptiform synchronization and thus ictogenesis, although with different features; (ii) the surprising ability of GABAB receptor antagonism to disclose ictal-like activity when excitatory ionotropic transmission is abolished; and (iii) their contribution to control seizure-like discharges during repetitive electrical stimuli delivered in limbic structures. In spite of this evidence, the role of GABAB receptor function in focal epileptic disorders has been attracting less interest when compared to the numerous studies that have addressed GABAA receptor signaling. Therefore, a main aim of our mini-review is to revive interest in the function of GABAB receptors in focal epilepsy research.

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