Abstract P201: Negative Regulation Of PVN Pre-sympathetic Neuronal Activity By Resident Microglia

Hypothalamic paraventricular nucleus (PVN) is a critical integrating region in controlling peripheral sympathetic tonicity. While the vast studies have unraveled the regulatory circuits affecting PVN pre-sympathetic neurons, local factors for maintaining the homeostasis of neuronal excitability are barely understood. In the present study we investigated the role of microglia, the primary resident immune cells of the CNS, in this context. By electrophysiological recording, we found that loss of resident microglia induced an increased firing frequency and attenuated outward potassium currents in the PVN pre-sympathetic neurons, tachycardia and impaired heart rate variability. Combining the transcriptomics analysis of the PVN microglia, we identified a releasable factor, which was dominantly expressed in microglia compared to other brain parenchymal cells. ICV infusion of the recombinant peptide restored potassium currents in the PVN pre-sympathetic neurons and autonomic function in microglia-depleted mice. In summary, our results provided a novel intrinsic regulatory mechanism by which microglia suppress neuronal over excitation in physiological condition.

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Neurons, Receptors, and Channels

The Annual Review of Pharmacology and Toxicology ◽

10.1146/annurev-pharmtox-010919-023755 ◽

2020 ◽

Vol 60 (1) ◽

pp. 9-30 ◽

Cited By ~ 1

Author(s):

David A. Brown

Keyword(s):

Messenger Rna ◽

Neuronal Excitability ◽

Single Channel ◽

Sympathetic Neurons ◽

Electrophysiological Recording ◽

Muscarinic Agonists ◽

M Current ◽

Antisense Knockdown ◽

Sympathetic Transmission ◽

Laboratory Life

Here, I recount some adventures that I and my colleagues have had over some 60 years since 1957 studying the effects of drugs and neurotransmitters on neuronal excitability and ion channel function, largely, but not exclusively, using sympathetic neurons as test objects. Studies include effects of centrally active drugs on sympathetic transmission; neuronal action and neuroglial uptake of GABA in the ganglia and brain; the action of muscarinic agonists on sympathetic neurons; the action of bradykinin on neuroblastoma-derived cells; and the identification of M-current as a target for muscarinic action, including experiments to determine its distribution, molecular composition, neurotransmitter sensitivity, and intracellular regulation by phospholipids and their hydrolysis products. Techniques used include electrophysiological recording (extracellular, intracellular microelectrode, whole-cell, and single-channel patch-clamp), autoradiography, messenger RNA and complementary DNA expression, antibody injection, antisense knockdown, and membrane-targeted lipidated peptides. I finish with some recollections about my scientific career, funding, and changes in laboratory life and pharmacology research over the past 60 years.

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Profound Alterations in the Intrinsic Excitability of Cerebellar Purkinje Neurons Following Neurotoxin 3-Acetylpyridine (3-AP)-Induced Ataxia in Rat: New Insights Into the Role of Small Conductance K+ Channels

Physiological Research ◽

10.33549/physiolres.932032 ◽

2011 ◽

pp. 355-365 ◽

Cited By ~ 6

Author(s):

M. KAFFASHIAN ◽

M. SHABANI ◽

I. GOUDARZI ◽

G. BEHZADI ◽

A. ZALI ◽

...

Keyword(s):

Neuronal Excitability ◽

Input Resistance ◽

Firing Frequency ◽

Discharge Frequency ◽

Sk Channels ◽

Intrinsic Properties ◽

K Channels ◽

Initial Discharge ◽

Small Conductance

Alterations in the intrinsic properties of Purkinje cells (PCs) may contribute to the abnormal motor performance observed in ataxic rats. To investigate whether such changes in the intrinsic neuronal excitability could be attributed to the role of Ca2+-activated K+ channels (KCa), whole cell current clamp recordings were made from PCs in cerebellar slices of control and ataxic rats. 3-AP induced profound alterations in the intrinsic properties of PCs, as evidenced by a significant increase in both the membrane input resistance and the initial discharge frequency, along with the disruption of the firing regularity. In control PCs, the blockade of small conductance KCa channels by UCL1684 resulted in a significant increase in the membrane input resistance, action potential (AP) half-width, time to peak of the AP and initial discharge frequency. SK channel blockade also significantly decreased the neuronal discharge regularity, the peak amplitude of the AP, the amplitude of the after- hyperpolarization and the spike frequency adaptation ratio. In contrast, in ataxic rats, both the firing regularity and the initial firing frequency were significantly increased by the blockade of SK channels. In conclusion, ataxia may arise from alterations in the functional contribution of SK channels, to the intrinsic properties of PCs.

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Inhibition of Hsp70 suppresses neuronal hyperexcitability and attenuates seizures by enhancing A-type potassium currents

10.1101/256602 ◽

2018 ◽

Author(s):

Fang Hu ◽

Jingheng Zhou ◽

Yanxin Lu ◽

Lizhao Guan ◽

Ning-ning Wei ◽

...

Keyword(s):

Hippocampal Neurons ◽

Neuronal Excitability ◽

Therapeutic Potential ◽

Potassium Currents ◽

Protective Role ◽

Neuronal Hyperexcitability ◽

Response To Stress ◽

Proteosomal Degradation ◽

Hsp70 Inhibitors

ABSTRACTThe heat shock protein 70 (Hsp70) is upregulated in response to stress and has been implicated as a stress marker in temporal lobe epilepsy (TLE). However, whether Hsp70 plays a pathologic or protective role in TLE remains unclear. Here we report that Hsp70 exerts an unexpected deleterious role in kainic acid (KA)-induced seizures, and inhibition of Hsp70 suppresses neuronal hyperexcitability and attenuates both acute and chronic seizures via enhancing A-type potassium currents primarily formed by Kv4 α-subunits and auxiliary KChIPs. Proteosomal degradation of Kv4-KChIP4a channel complexes is enhanced by Hsp70, which can be reversed by the Hsp70 inhibitors, 2-phenylethynesulfonamide (PES) and VER-155008 (VER). In cultured hippocampal neurons, either PES or VER can increase A-type Kv4 current to suppress neuronal hyperexcitability. Mechanistically, Hsp70-CHIP complexes directly bind to the N-terminus of auxiliary KChIP4a and target Kv4-KChIP4a complexes to the proteasome. Our findings reveal a previously unrecognized role of Hsp70 in mediating degradation of Kv4-KChIP4a complexes and regulating neuronal excitability, thus highlighting a therapeutic potential for hyperexcitability-related neurological disorders through Hsp70 inhibition.

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Dysregulation of Astrocyte–Neuronal Communication in Alzheimer’s Disease

International Journal of Molecular Sciences ◽

10.3390/ijms22157887 ◽

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.

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The neuro-cardiac junction defines an extracellular microdomain required for neurotrophic signaling

European Heart Journal ◽

10.1093/ehjci/ehaa946.3589 ◽

2020 ◽

Vol 41 (Supplement_2) ◽

Author(s):

M Mongillo ◽

M Franzoso ◽

V Prando ◽

L Dokshokova ◽

A Di Bona ◽

...

Keyword(s):

Culture Medium ◽

Heart Diseases ◽

Sympathetic Neurons ◽

Confocal Imaging ◽

Public Institution ◽

Mdx Mice ◽

Mouse Heart ◽

Funding Source ◽

Neurotrophic Signaling

Abstract Background Sympathetic neurons (SNs) innervate the myocardium with a defined topology that allows physiological modulation of cardiac activity. Neurotrophins released by cardiac cells control SN viability and myocardial distribution, which are impaired in heart diseases with reduced (e.g. heart failure) or heterogenous sympathetic stimulation (e.g. arrhythmias). We previously demonstrated that SNs interact directly with cardiomyocytes (CMs) at neuro-cardiac junctions (NCJ), and such structured contact sites allow neurons to efficiently activate β-adrenoceptors on the myocyte membrane. Aims We here asked whether NCJs are functional for retrograde (myocyte to neuron) neurotrophic signaling. Methods and results Electron microscopy and immunofluorescence on mouse heart slices and SN/CM co-cultures showed that the NGF receptor, TrkA, is preferentially found in correspondence of the NCJ. Consistently, neurons taking structured contact with CMs showed fast TrkA activation and its retrograde transport to the soma, which was monitored using live confocal imaging in cells expressing TrkA-RFP. In accord with NGF dependent effects, CM-contacted SN showed larger synaptic varicosities and did not require NGF supplementation in the culture medium. In support that NGF locally released at NCJs sustains SN viability, the neurotrophin concentration in the culture medium was 1.61 pg/mL, and did not suffice to maintain neuronal viability, which was also perturbed (66% decrease of neuronal density) by silencing NGF expression in CMs. These results support that the NCJ is essential for intercellular neurotrophin signaling. Consistently, by applying competitive inhibition of TrkA with increasing doses of K252a, we estimated NGF concentration at the contact site to be about 1000-fold higher than that released by CM in the culture medium. To seek for the structural determinants of the NCJ, we focused on dystrophin, based on the finding that the protein accumulates on the CM membrane portion contacted by SNs, as observed in mouse heart slices, and co-cultured CMs. In support of a role of CM-expressed dystrophin in neurotrophic signaling, hearts from dystrophin-KO (mdx) mice showed 74.36% decrease of innervation, with no significant changes of NGF expression. In line with the purported role of NCJs, in co-cultures between wild type SNs and mdx CMs, TrkA activation (TrkA movements toward SN soma (%): WTCM-WTSN=18±4; MDXCM-WTSN= 12±3; p<0,05) and neuronal survival were reduced. Conclusions Taken together, our results suggest that NGF-dependent signaling to SNs requires a direct and specialized interaction with myocytes, and that loss of dystrophin at the CM membrane impairs retrograde signaling to the neurons leading to cardiac sympathetic dys-innervation. Funding Acknowledgement Type of funding source: Public Institution(s). Main funding source(s): University of Padova

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Studies on the Role of the are a Gene in the Regulation of Nitrogen Catabolism in Aspergillus nidulans

Australian Journal of Biological Sciences ◽

10.1071/bi9750301 ◽

1975 ◽

Vol 28 (3) ◽

pp. 301 ◽

Cited By ~ 84

Author(s):

MJ Hynes

Keyword(s):

Nitrogen Source ◽

Aspergillus Nidulans ◽

Carbon Sources ◽

Nitrogen Sources ◽

Selection Methods ◽

Growth Responses ◽

Dominance Relationships ◽

Regulatory Circuits ◽

Specific Activities

Mutants of Apergillus nidulanswith lesions in a gene, areA (formerly called amdT), have been isolated by a variety of different selection methods. The areA mutants show a range of pleiotropic growth responses to a number of compounds as sole nitrogen sources, but are normal in utilization of carbon sources. The levels of two amidase enzymes as well as urease have been investigated in the mutants and have been shown to be affected by this gene. Most of the areA mutants have much lower amidase-specific activities when grown in ammonium-containing medium, compared with mycelium incubated in medium la9king a nitrogen source. Some of the areA. mutants do not show derepression of urease upon relief of ammonium repression. The dominance relationships of areA alleles have been investigated in� heterozygous diploids, and these studies lend support to the proposal that areA codes for a positively acting regulatory product. One of the new areA alleles is partially dominant to areA + and areA102. This may be a result of negative complementation or indicate that areA has an additional negative reiuIatory function. Investigation.of various amdR; areA double mutants has led to the conclusion that amdR and areA participate in independent regulatory circuits in the control of acetamide utilizatiol1. Studies on an amdRc; areA.double mutant indicate that areA is involved in derepression of acetamidase upon relief of ammo.nium repression.

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

Journal of Neurophysiology ◽

10.1152/jn.01098.2007 ◽

2008 ◽

Vol 99 (6) ◽

pp. 2985-2997 ◽

Cited By ~ 66

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.

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