scholarly journals Subunit-Specific Effects of Isoflurane on Neuronal Ih in HCN1 Knockout Mice

2009 ◽  
Vol 101 (1) ◽  
pp. 129-140 ◽  
Author(s):  
Xiangdong Chen ◽  
Shaofang Shu ◽  
Dylan P. Kennedy ◽  
Sarah C. Willcox ◽  
Douglas A. Bayliss
Keyword(s):  
Knockout Mice ◽  
Cortical Neurons ◽  
Current Amplitude ◽  
Membrane Properties ◽  
Neuronal Membrane ◽  
Hcn Channels ◽  
Wild Type ◽  
General Anesthetic ◽  
Cationic Current ◽  
Knockout Animals

The ionic mechanisms that contribute to general anesthetic actions have not been elucidated, although increasing evidence has pointed to roles for subthreshold ion channels, such as the HCN channels underlying the neuronal hyperpolarization-activated cationic current ( Ih). Here, we used conventional HCN1 knockout mice to test directly the contributions of specific HCN subunits to effects of isoflurane, an inhalational anesthetic, on membrane and integrative properties of motor and cortical pyramidal neurons in vitro. Compared with wild-type mice, residual Ih from knockout animals was smaller in amplitude and presented with HCN2-like properties. Inhibition of Ih by isoflurane previously attributed to HCN1 subunit-containing channels (i.e., a hyperpolarizing shift in half-activation voltage [ V1/2]) was absent in neurons from HCN1 knockout animals; the remaining inhibition of current amplitude could be attributed to effects on residual HCN2 channels. We also found that isoflurane increased temporal summation of excitatory postsynaptic potentials (EPSPs) in cortical neurons from wild-type mice; this effect was predicted by simulation of anesthetic-induced dendritic Ih inhibition, which also revealed more prominent summation accompanying shifts in V1/2 (an HCN1-like effect) than decreased current amplitude (an HCN2-like effect). Accordingly, anesthetic-induced EPSP summation was not observed in cortical cells from HCN1 knockout mice. In wild-type mice, the enhanced synaptic summation observed with low concentrations of isoflurane contributed to a net increase in cortical neuron excitability. In summary, HCN channel subunits account for distinct anesthetic effects on neuronal membrane properties and synaptic integration; inhibition of HCN1 in cortical neurons may contribute to the synaptically mediated slow-wave cortical synchronization that accompanies anesthetic-induced hypnosis.

Suppression of Ih Contributes to Propofol-Induced Inhibition of Mouse Cortical Pyramidal Neurons

2005 ◽  
Vol 94 (6) ◽  
pp. 3872-3883 ◽  
Author(s):  
Xiangdong Chen ◽  
Shaofang Shu ◽  
Douglas A. Bayliss
Keyword(s):  
Cortical Neurons ◽  
Pyramidal Neurons ◽  
Brain Slices ◽  
Current Amplitude ◽  
Hcn Channels ◽  
General Anesthetic ◽  
Large Shift ◽  
Fast Kinetics ◽  
Membrane Hyperpolarization ◽  
Cortical Pyramidal Neurons

The contributions of the hyperpolarization-activated current, Ih, to generation of rhythmic activities are well described for various central neurons, particularly in thalamocortical circuits. In the present study, we investigated effects of a general anesthetic, propofol, on native Ih in neurons of thalamus and cortex and on the corresponding cloned HCN channel subunits. Whole cell voltage-clamp recordings from mouse brain slices identified neuronal Ih currents with fast activation kinetics in neocortical pyramidal neurons and with slower kinetics in thalamocortical relay cells. Propofol inhibited the fast-activating Ih in cortical neurons at a clinically relevant concentration (5 μM); inhibition of Ih involved a hyperpolarizing shift in half-activation voltage (Δ V1/2 approximately −9 mV) and a decrease in maximal available current (∼36% inhibition, measured at −120 mV). With the slower form of Ih expressed in thalamocortical neurons, propofol had no effect on current activation or amplitude. In heterologous expression systems, 5 μM propofol caused a large shift in V1/2 and decrease in current amplitude in homomeric HCN1 and linked heteromeric HCN1–HCN2 channels, both of which activate with fast kinetics but did not affect V1/2 or current amplitude of slowly activating homomeric HCN2 channels. With GABAA and glycine receptor channels blocked, propofol caused membrane hyperpolarization and suppressed action potential discharge in cortical neurons; these effects were occluded by the Ih blocker, ZD-7288. In summary, these data indicate that propofol selectively inhibits HCN channels containing HCN1 subunits, such as those that mediate Ih in cortical pyramidal neurons—and they suggest that anesthetic actions of propofol may involve inhibition of cortical neurons and perhaps other HCN1-expressing cells.

Lack of a Requirement for the Inhibitory Fcγ Receptor In IVIG-Mediated Treatment of ITP

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3338-3338
Author(s):  
Danila Leontyev ◽  
Yulia Katsman ◽  
Xue-Zhong Ma ◽  
Donald R. Branch
Keyword(s):  
Knockout Mice ◽  
Conflicts Of Interest ◽  
Inflammatory Diseases ◽  
Ivig Therapy ◽  
Ivig Treatment ◽  
Wild Type ◽  
Fcγ Receptor ◽  
Antiplatelet Antibody ◽  
And Function ◽  
Knockout Animals

Abstract Abstract 3338 One of the most quoted articles in publications and at International meetings regarding the mechanism of intravenous immunoglobulin (IVIg) therapy in autoimmune and inflammatory diseases is that by Samuelsson et al., Science 291, 484 (2001). This article deals with the mechanism of effect of IVIg being due to an increase in the expression and function of the inhibitory Fcγ receptor (FcγRIIB) in splenic macrophages. The conclusions in this Science paper are based primarily on the use of an experimental mouse model of immune thrombocytopenia (ITP) and mice made deficient in FcγRIIB (FcγRIIB-/- knockouts). We have not been able to support these previous findings but instead find the presence of FcγRIIB receptor not necessary for successful treatment of experimental ITP through IVIg treatment. Administration of IVIg to wild-type Balb/c mice previously made thrombocytopenic using an escalating dose of antiplatelet antibody, MWReg30, leads to amelioration of experimental ITP while in untreated mice, platelet counts stay close to nadir. Similar dynamics of the amelioration of ITP were found using splenectomized or FcγRIIB-/- knockout (Taconic Labs) Balb/c mice. However, as previously published (Blood 15, 558 (2003)), IVIg does not work with FcγRIIB-/- knockout mice that are on a mixed B6:129S4 background, obtained from the Jackson Labs. Indeed, B6 (129S4-Fcgr2btm1Rav/J) FcγRIIB-/- knockout mice made thrombocytopenic are completely unresponsive to IVIg treatment. However, surprisingly, when using the recommended control wild-type mice for this knockout, the B6.129SF2 mouse, we found that this wild-type FcγRIIB+/+ mouse also does not respond to IVIg treatment. Confirmation of genotype was done; thus, we suggest that something about the 129S background prevents a response to IVIg therapy and this phenomenon is independent of the FcγRIIB. We have confirmed that wild-type 129S4 mice made thrombocytopenic do not respond to IVIg. We have also examined the B6 FcγRIIB-/- knockout mice from Taconic Labs which are purported to be fully congenic and these mice also do not respond to IVIg. Because of the lack of response to IVIg of wild-type 129S4 mice, we believe that the Taconic B6 FcγRIIB-/- knockout mice may, in fact, be mixed background as are the Jackson mice. Thus, we plan to use SNP protocols for determination of congenicity, comparing C57BL/6 and 129S4 strains to Taconic and Jackson Labs B6 FcγRIIB-/- knockout mice. We expect to show that both B6 FcγRIIB-/- knockout animals are not fully congenic, being a mixture of both C57BL/6 and 129S4 strains. Previous publications that indicated a lack of response to IVIg using FcγRIIB-/- knockout mice either did not test the fully congenic Taconic Balb/c knockouts and/or failed to use the most suitable control animals with the nonfully congenic B6 knockouts, using instead, C57BL/6 wild-type mice which respond well to IVIg treatment. In order to avoid misinterpretation of results, all experiments testing the role for FcγRIIB in the mechanism of IVIg should be done using Taconic Balb/c FcγRIIB-/- knockout mice until congenicity can be established with the B6 knockout animals. These data taken together lead us to the conclusion that the presence of the FcγRIIB receptor is not important for the therapeutic action of IVIg. Disclosures: No relevant conflicts of interest to declare.

scholarly journals Soticlestat, a novel cholesterol 24-hydroxylase inhibitor shows a therapeutic potential for neural hyperexcitation in mice

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Toshiya Nishi ◽  
Shinichi Kondo ◽  
Maki Miyamoto ◽  
Sayuri Watanabe ◽  
Shigeo Hasegawa ◽  
...  
Keyword(s):  
Knockout Mice ◽  
Brain Slice ◽  
Therapeutic Potential ◽  
Dependent Manner ◽  
Wild Type ◽  
Short Life Span ◽  
Premature Deaths ◽  
Knockout Animals ◽  
Dose Dependent ◽  
The Brain

Abstract Cholesterol 24-hydroxylase (CH24H) is a brain-specific enzyme that converts cholesterol into 24S-hydroxycholesterol, the primary mechanism of cholesterol catabolism in the brain. The therapeutic potential of CH24H activation has been extensively investigated, whereas the effects of CH24H inhibition remain poorly characterized. In this study, the therapeutic potential of CH24H inhibition was investigated using a newly identified small molecule, soticlestat (TAK-935/OV935). The biodistribution and target engagement of soticlestat was assessed in mice. CH24H-knockout mice showed a substantially lower level of soticlestat distribution in the brain than wild-type controls. Furthermore, brain-slice autoradiography studies demonstrated the absence of [3H]soticlestat staining in CH24H-knockout mice compared with wild-type mice, indicating a specificity of soticlestat binding to CH24H. The pharmacodynamic effects of soticlestat were characterized in a transgenic mouse model carrying mutated human amyloid precursor protein and presenilin 1 (APP/PS1-Tg). These mice, with excitatory/inhibitory imbalance and short life-span, yielded a remarkable survival benefit when bred with CH24H-knockout animals. Soticlestat lowered brain 24S-hydroxycholesterol in a dose-dependent manner and substantially reduced premature deaths of APP/PS1-Tg mice at a dose lowering brain 24S-hydroxycholesterol by approximately 50%. Furthermore, microdialysis experiments showed that soticlestat can suppress potassium-evoked extracellular glutamate elevations in the hippocampus. Taken together, these data suggest that soticlestat-mediated inhibition of CH24H may have therapeutic potential for diseases associated with neural hyperexcitation.

Effect of N -methyl-d-aspartate Receptor ε1Subunit Gene Disruption of the Action of General Anesthetic Drugs in Mice

2005 ◽  
Vol 102 (3) ◽  
pp. 557-561 ◽  
Author(s):  
Yuki Sato ◽  
Eiji Kobayashi ◽  
Takanori Murayama ◽  
Masayoshi Mishina ◽  
Norimasa Seo
Keyword(s):  
Nitrous Oxide ◽  
Nmda Receptor ◽  
Knockout Mice ◽  
Gamma Aminobutyric Acid ◽  
Wild Type ◽  
General Anesthetic ◽  
Hypnotic Effect ◽  
Anesthetic Agents ◽  
Anesthetic Drugs

Background Recent molecular strategies demonstrated that the N-methyl-d-aspartate (NMDA) receptor is a major target site of anesthetic agents. In a previous article, the authors showed that knocking out the NMDA receptor epsilon1 subunit gene markedly reduced the hypnotic effect of ketamine in mice. In the current study, the authors examined the in vivo contribution of the NMDA receptor epsilon1 subunit to the action of other anesthetic drugs. Methods The authors determined the anesthetic effects of nitrous oxide on sevoflurane potency in NMDA receptor epsilon1 subunit knockout mice compared with those in wild-type mice. They then tested the hypnotic effect of gamma-aminobutyric acid-mediated agents, such as propofol, pentobarbital, diazepam, and midazolam, in knockout mice and wild-type mice. Results The anesthetic action of sevoflurane itself was unaffected by the abrogation of the NMDA receptor epsilon1 subunit. Adding nitrous oxide reduced the required concentration of sevoflurane to induce anesthesia in wild-type mice, whereas this sparing effect was diminished in knockout mice. Furthermore, propofol, pentobarbital, diazepam, and midazolam also had markedly attenuated effects in knockout mice. Conclusions Although it has been demonstrated that knocking out the expression of receptors may induce changes in the composition of the subunits, the network circuitry, or both, the current findings show consistently that the NMDA receptor epsilon1 subunit mediates nitrous oxide but not sevoflurane anesthesia. Furthermore, the attenuated anesthetic impact of propofol, pentobarbital, diazepam, and midazolam as well as ketamine in knockout mice suggests that the NMDA receptor epsilon1 subunit could be indirectly involved in the hypnotic action of these drugs in vivo.

Laminar distribution of neuronal membrane properties in neocortex of normal and reeler mouse

1991 ◽  
Vol 66 (6) ◽  
pp. 2034-2040 ◽  
Author(s):  
L. R. Silva ◽  
M. J. Gutnick ◽  
B. W. Connors
Keyword(s):  
Cortical Neurons ◽  
Normal Mouse ◽  
Membrane Properties ◽  
Recessive Mutation ◽  
Neuronal Membrane ◽  
Firing Patterns ◽  
Postsynaptic Potentials ◽  
Intrinsic Firing ◽  
Synaptic Responses

1. Reeler is an autosomal recessive mutation of mice that alters neuronal migration during development, yielding a general inversion of the laminae in the neocortex. We recorded in vitro from slices of normal and reeler neocortex to study the influence of neuron position and shape on membrane properties and synaptic responses. 2. The intrinsic firing patterns, action-potential shapes, resting membrane potentials, input resistances, and evoked excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) did not differ between reelers and controls when data were grouped. 3. The depth distribution of intrinsic firing patterns was inverted in the reeler: intrinsically bursting (IB) neurons were found only in layer 5 in the normal mouse, but they were found exclusively in supragranular layers of the reeler cortex. 4. The spatial distribution of synaptic responses in the reeler was also inverted: very prominent IPSPs were characteristic of upper layer neurons in the normal mouse, but in the reeler similar inhibitory responses were observed predominantly in deep infragranular layers. 5. Dye injections in reeler pyramidal neurons revealed atypical morphologies, including distorted apical dendrites and cell inversion. 6. The data imply that cortical neurons develop the membrane and synaptic properties appropriate to their function, despite being malformed and mispositioned.

scholarly journals BACE inhibitor treatment of mice induces hyperactivity in a Seizure-related gene 6 family dependent manner without altering learning and memory

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. Nash ◽  
H. J. M. Gijsen ◽  
B. J. Hrupka ◽  
K. S.-L. Teng ◽  
S. F. Lichtenthaler ◽  
...  
Keyword(s):  
Cognitive Flexibility ◽  
Dendritic Spine ◽  
Knockout Mice ◽  
Cortical Neurons ◽  
Dependent Manner ◽  
Spine Density ◽  
Related Gene ◽  
Wild Type ◽  
Bace Inhibitor ◽  
Inhibitor Treatment

AbstractBACE inhibitors, which decrease BACE1 (β-secretase 1) cleavage of the amyloid precursor protein, are a potential treatment for Alzheimer’s disease. Clinical trials using BACE inhibitors have reported a lack of positive effect on patient symptoms and, in some cases, have led to increased adverse events, cognitive worsening and hippocampal atrophy. A potential drawback of this strategy is the effect of BACE inhibition on other BACE1 substrates such as Seizure-related gene 6 (Sez6) family proteins which are known to have a role in neuronal function. Mice were treated with an in-diet BACE inhibitor for 4–8 weeks to achieve a clinically-relevant level of amyloid-β40 reduction in the brain. Mice underwent behavioural testing and postmortem analysis of dendritic spine number and morphology with Golgi-Cox staining. Sez6 family triple knockout mice were tested alongside wild-type mice to identify whether any effects of the treatment were due to altered cleavage of Sez6 family proteins. Wild-type mice treated with BACE inhibitor displayed hyperactivity on the elevated open field, as indicated by greater distance travelled, but this effect was not observed in treated Sez6 triple knockout mice. BACE inhibitor treatment did not lead to significant changes in spatial or fear learning, reference memory, cognitive flexibility or anxiety in mice as assessed by the Morris water maze, context fear conditioning, or light–dark box tests. Chronic BACE inhibitor treatment reduced the density of mushroom-type spines in the somatosensory cortex, regardless of genotype, but did not affect steady-state dendritic spine density or morphology in the CA1 region of the hippocampus. Chronic BACE inhibition for 1–2 months in mice led to increased locomotor output but did not alter memory or cognitive flexibility. While the mechanism underlying the treatment-induced hyperactivity is unknown, the absence of this response in Sez6 triple knockout mice indicates that blocking ectodomain shedding of Sez6 family proteins is a contributing factor. In contrast, the decrease in mature spine density in cortical neurons was not attributable to lack of shed Sez6 family protein ectodomains. Therefore, other BACE1 substrates are implicated in this effect and, potentially, in the cognitive decline in longer-term chronically treated patients.

scholarly journals IL-17F depletion accelerates chitosan conduit guided peripheral nerve regeneration

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Feixiang Chen ◽  
Weihuang Liu ◽  
Qiang Zhang ◽  
Ping Wu ◽  
Ao Xiao ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Sciatic Nerve ◽  
Peripheral Nerve ◽  
Nerve Regeneration ◽  
Knockout Mice ◽  
Inflammatory Markers ◽  
Nerve Repair ◽  
Peripheral Nerve Regeneration ◽  
Wild Type ◽  
Anti Inflammatory

AbstractPeripheral nerve injury is a serious health problem and repairing long nerve deficits remains a clinical challenge nowadays. Nerve guidance conduit (NGC) serves as the most promising alternative therapy strategy to autografts but its repairing efficiency needs improvement. In this study, we investigated whether modulating the immune microenvironment by Interleukin-17F (IL-17F) could promote NGC mediated peripheral nerve repair. Chitosan conduits were used to bridge sciatic nerve defect in IL-17F knockout mice and wild-type mice with autografts as controls. Our data revealed that IL-17F knockout mice had improved functional recovery and axonal regeneration of sciatic nerve bridged by chitosan conduits comparing to the wild-type mice. Notably, IL-17F knockout mice had enhanced anti-inflammatory macrophages in the NGC repairing microenvironment. In vitro data revealed that IL-17F knockout peritoneal and bone marrow derived macrophages had increased anti-inflammatory markers after treatment with the extracts from chitosan conduits, while higher pro-inflammatory markers were detected in the Raw264.7 macrophage cell line, wild-type peritoneal and bone marrow derived macrophages after the same treatment. The biased anti-inflammatory phenotype of macrophages by IL-17F knockout probably contributed to the improved chitosan conduit guided sciatic nerve regeneration. Additionally, IL-17F could enhance pro-inflammatory factors production in Raw264.7 cells and wild-type peritoneal macrophages. Altogether, IL-17F may partially mediate chitosan conduit induced pro-inflammatory polarization of macrophages during nerve repair. These results not only revealed a role of IL-17F in macrophage function, but also provided a unique and promising target, IL-17F, to modulate the microenvironment and enhance the peripheral nerve regeneration.

Ascorbic acid and CoQ10 ameliorate the reproductive ability of superoxide dismutase 1-deficient female mice†

2019 ◽  
Author(s):  
Naoki Ishii ◽  
Takujiro Homma ◽  
Jaeyong Lee ◽  
Hikaru Mitsuhashi ◽  
Ken-ichi Yamada ◽  
...  
Keyword(s):  
Ascorbic Acid ◽  
Superoxide Dismutase ◽  
Coenzyme Q10 ◽  
Knockout Mice ◽  
Knockout Mouse ◽  
Superoxide Dismutase 1 ◽  
Wild Type ◽  
Positive Effects ◽  
Reproductive Ability ◽  
Ascorbic Acid Supplementation

Abstract Superoxide dismutase 1 suppresses oxidative stress within cells by decreasing the levels of superoxide anions. A dysfunction of the ovary and/or an aberrant production of sex hormones are suspected causes for infertility in superoxide dismutase 1-knockout mice. We report on attempts to rescue the infertility in female knockout mice by providing two antioxidants, ascorbic acid and/or coenzyme Q10, as supplements in the drinking water of the knockout mice after weaning and on an investigation of their reproductive ability. On the first parturition, 80% of the untreated knockout mice produced smaller litter sizes compared with wild-type mice (average 2.8 vs 7.3 pups/mouse), and supplementing with these antioxidants failed to improve these litter sizes. However, in the second parturition of the knockout mice, the parturition rate was increased from 18% to 44–75% as the result of the administration of antioxidants. While plasma levels of progesterone at 7.5 days of pregnancy were essentially the same between the wild-type and knockout mice and were not changed by the supplementation of these antioxidants, sizes of corpus luteum cells, which were smaller in the knockout mouse ovaries after the first parturition, were significantly ameliorated in the knockout mouse with the administration of the antioxidants. Moreover, the impaired vasculogenesis in uterus/placenta was also improved by ascorbic acid supplementation. We thus conclude that ascorbic acid and/or coenzyme Q10 are involved in maintaining ovarian and uterus/placenta homeostasis against insults that are augmented during pregnancy and that their use might have positive effects in terms of improving female fertility.

Negative impact of tissue inhibitor of metalloproteinase-3 null mutation on lung structure and function in response to sepsis

2003 ◽  
Vol 285 (6) ◽  
pp. L1222-L1232 ◽  
Author(s):  
Erica L. Martin ◽  
Brent Z. Moyer ◽  
M. Cynthia Pape ◽  
Barry Starcher ◽  
Kevin J. Leco ◽  
...  
Keyword(s):  
Negative Impact ◽  
Cecal Ligation ◽  
Lung Compliance ◽  
Tissue Inhibitor Of Metalloproteinase ◽  
Tissue Inhibitors Of Metalloproteinases ◽  
Wild Type ◽  
Gelatinase Activity ◽  
Lung Structure ◽  
And Function ◽  
Knockout Animals

Matrix metalloproteinases (MMPs) are degradative enzymes, which act to remodel tissue. Their activity is regulated by the tissue inhibitors of metalloproteinases (TIMPs). An imbalance in the degradation/inhibition activities has been associated with many diseases, including sepsis. We have previously shown that TIMP-3 knockout animals develop spontaneous, progressive air space enlargement. The objectives of this study were to determine the effects of a septic lung stress induced by cecal ligation and perforation (CLP) on lung function, structure, pulmonary surfactant, and inflammation in TIMP-3 null mice. Knockout and wild-type animals were randomized to either sham or CLP surgery, allowed to recover for 6 h, and then euthanized. TIMP-3 null animals exposed to sham surgery had a significant increase in lung compliance when compared with sham wild-type mice. Additionally, the TIMP-3 knockout mice showed a significant increase in compliance following CLP. Rapid compliance changes were accompanied by significantly decreased collagen and fibronectin levels and increased gelatinase (MMP-2 and -9) abundance and activation. Additionally, in situ zymography showed increased airway-associated gelatinase activity in the knockout animals enhanced following CLP. In conclusion, exposing TIMP-3 null animals to sepsis rapidly enhances the phenotypic abnormalities of these mice, due to increased MMP activity induced by CLP.

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