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Max F Oginsky, Ningren Cui, Weiwei Zhong, Christopher M Johnson, Chun Jiang
People with Rett syndrome (RTT) have defects in motor function also seen in Mecp2-null mice. Motor function depends on not only central motor commands but also sensory feedback that is vulnerable to changes in excitability of propriosensory neurons. Here we report evidence for hyperexcitability of mesencephalic trigeminal (Me5) neurons in Mecp2-null mice and a novel cellular mechanism for lowering its impact. In in-vitro brain slices, the Me5 neurons in both Mecp2(-/Y) male and symptomatic Mecp2(+/-) female mice were overly excitable showing increased firing activity in comparison to their wild-type (WT) male and asymptomatic counterparts...
September 27, 2016: Journal of Cellular Physiology
Christoforos Tsantoulas, Elizabeth R Mooney, Peter A McNaughton
Nociception - the ability to detect painful stimuli - is an invaluable sense that warns against present or imminent damage. In patients with chronic pain, however, this warning signal persists in the absence of any genuine threat and affects all aspects of everyday life. Neuropathic pain, a form of chronic pain caused by damage to sensory nerves themselves, is dishearteningly refractory to drugs that may work in other types of pain and is a major unmet medical need begging for novel analgesics. Hyperpolarisation-activated cyclic nucleotide (HCN)-modulated ion channels are best known for their fundamental pacemaker role in the heart; here, we review data demonstrating that the HCN2 isoform acts in an analogous way as a 'pacemaker for pain', in that its activity in nociceptive neurons is critical for the maintenance of electrical activity and for the sensation of chronic pain in pathological pain states...
September 15, 2016: Biochemical Journal
Rafael Zúñiga, Daniela González, Claudio Valenzuela, Nelson Brown, Leandro Zúñiga
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels belong to the superfamily of voltage-gated pore loop channels. In mammals, this family consists of four different subunits (HCN1-4) and their ion channels activity have been proposed to play an essential role in regulating the membrane potential of excitable cells. Here, we describe the expression and relative abundances of HCN channels in cerebellum and primary cultures of cerebellar granule neurons (CGN). Quantitative determination of mRNA expression levels demonstrated the existence of an accumulation pattern of transcripts in cerebellum that encode HCN2 > HCN3 = HCN4 > HCN1 subunits...
September 23, 2016: Biochemical and Biophysical Research Communications
Leo C T Ng, Igor Putrenko, Victoria Baronas, Filip Van Petegem, Eric A Accili
Cyclic AMP is thought to facilitate the opening of the HCN2 channel by binding to a C-terminal domain and promoting or inhibiting interactions between subunits. Here, we correlated the ability of cyclic nucleotides to promote interactions of isolated HCN2 C-terminal domains in solution with their ability to facilitate channel opening. Cyclic IMP, a cyclic purine nucleotide, and cCMP, a cyclic pyrimidine nucleotide, bind to a C-terminal domain containing the cyclic nucleotide-binding domain but, in contrast to other cyclic nucleotides examined, fail to promote its oligomerization, and produce only modest facilitation of opening of the full-length channel...
October 4, 2016: Structure
Amy L Brewster, Kyle Marzec, Alexandria Hairston, Marvin Ho, Anne E Anderson, Yi-Chen Lai
OBJECTIVES: A myriad of acute and chronic cardiac alterations are associated with status epilepticus (SE) including increased sympathetic tone, rhythm and ventricular repolarization disturbances. Despite these observations, the molecular processes underlying SE-associated myocardial remodeling remain to be identified. Here we determined early SE-associated myocardial electrical and molecular alterations using a model of SE and acquired epilepsy. METHODS: We performed electrocardiography (ECG) assessments in rats beginning at 2 weeks following kainate-induced SE, and calculated short-term variability (STV) of the corrected QT intervals (QTc) as a marker of ventricular stability...
August 24, 2016: Epilepsia
Weihua Ding, Zerong You, Shiqian Shen, Lucy Chen, Shengmei Zhu, Jianren Mao
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels regulate neuronal excitability in both peripheral and central nerve systems. Emerging evidence indicates that HCN channels are involved in the development and maintenance of chronic pain. However, the impact of HCN channel activity in the thalamus on chronic pain has not been examined. In this report, we evaluated the effect on nociceptive behaviors after infusion of a HCN channel blocker ZD7288 into the ventral posterolateral (VPL) nucleus of the thalamus in rats with neuropathic pain or monoarthritis...
September 19, 2016: Neuroscience Letters
Chang Liu, Changan Xie, Khade Grant, Zhuocheng Su, Weihua Gao, Qinglian Liu, Lei Zhou
Counting ion channels on cell membranes is of fundamental importance for the study of channel biophysics. Channel counting has thus far been tackled by classical approaches, such as radioactive labeling of ion channels with blockers, gating current measurements, and nonstationary noise analysis. Here, we develop a counting method based on patch-clamp fluorometry (PCF), which enables simultaneous electrical and optical recordings, and apply it to EGFP-tagged, hyperpolarization-activated and cyclic nucleotide-regulated (HCN) channels...
July 2016: Journal of General Physiology
Wei He, Jian Zhang, Tianyi Gan, Guojun Xu, Baopeng Tang
The aim of the present study was to analyze the mRNA and protein expression levels of atrial hyperpolarization-activated cyclic nucleotide-gated (HCN) channel isoforms in the left atrial muscle of dogs with multiple organ failure. A total of 14 beagle dogs with multiple organ failure, including seven cases with sinus rhythm and seven cases with atrial fibrillation (AF), underwent surgery to remove a sample of left atrial appendage tissue. The expression levels of a number of HCN channel subtypes were subsequently measured using quantitative polymerase chain reaction and western blot analysis...
July 2016: Experimental and Therapeutic Medicine
Shizhang Ling, Eleni M Rettig, Marietta Tan, Xiaofei Chang, Zhiming Wang, Mariana Brait, Justin A Bishop, Elana J Fertig, Michael Considine, Michael J Wick, Patrick K Ha
Salivary gland adenoid cystic carcinoma (ACC) is a rare head and neck malignancy without molecular biomarkers that can be used to predict the chemotherapeutic response or prognosis of ACC. The regulation of gene expression of oncogenes and tumor suppressor genes (TSGs) through DNA promoter methylation may play a role in the carcinogenesis of ACC. To identify differentially methylated genes in ACC, a global demethylating agent, 5-aza-2'-deoxycytidine (5-AZA) was utilized to unmask putative TSG silencing in ACC xenograft models in mice...
July 2016: International Journal of Oncology
Ieva Bruzauskaite, Daiva Bironaite, Edvardas Bagdonas, Vytenis Arvydas Skeberdis, Jaroslav Denkovskij, Tomas Tamulevicius, Valentinas Uvarovas, Eiva Bernotiene
BACKGROUND: The transfection of human mesenchymal stem cells (hMSCs) with the hyperpolarization-activated cyclic nucleotide-gated ion channel 2 (HCN2) gene has been demonstrated to provide biological pacing in dogs with complete heart block. The mechanism appears to be the generation of the ion current (If) by the HCN2-expressing hMSCs. However, it is not clear how the transfection process and/or the HCN2 gene affect the growth functions of the hMSCs. Therefore, we investigated survival, proliferation, cell cycle, and growth on a Kapton® scaffold of HCN2-expressing hMSCs...
2016: Stem Cell Research & Therapy
Francesco Resta, Alessio Masi, Maria Sili, Annunziatina Laurino, Flavio Moroni, Guido Mannaioni
Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels have a key role in the control of cellular excitability. HCN2, a subgroup of the HCN family channels, are heavily expressed in small dorsal root ganglia (DRG) neurons and their activation seems to be important in the determination of pain intensity. Intracellular elevation of cAMP levels activates HCN-mediated current (Ih) and small DRG neurons excitability. GPR35, a Gi/o coupled receptor, is highly expressed in small DRG neurons, and we hypothesized that its activation, mediated by endogenous or exogenous ligands, could lead to pain control trough a reduction of Ih current...
September 2016: Neuropharmacology
Pan Luo, Cheng Chen, Yun Lu, TianLi Fu, Qing Lu, Xulin Xu, Changjun Li, Zhi He, Lianjun Guo
Chronic cerebral hypoperfusion (CCH) causes memory deficits and increases the risk of vascular dementia (VD) through several biologically plausible pathways. However, whether CCH causes prefrontal cortex (PFC)-dependent spatial working memory impairments and Baclofen, a GABAB receptor agonist, could ameliorate the impairments is still not clear especially the mechanisms underlying the process. In this study, rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO) to induce CCH...
July 15, 2016: Behavioural Brain Research
Jing Fan, Patrick L Stemkowski, Maria A Gandini, Stefanie A Black, Zizhen Zhang, Ivana A Souza, Lina Chen, Gerald W Zamponi
Genetic ablation of cellular prion protein (PrP(C)) has been linked to increased neuronal excitability and synaptic activity in the hippocampus. We have previously shown that synaptic activity in hippocampi of PrP-null mice is increased due to enhanced N-methyl-D-aspartate receptor (NMDAR) function. Here, we focused on the effect of PRNP gene knock-out (KO) on intrinsic neuronal excitability, and in particular, the underlying ionic mechanism in hippocampal neurons cultured from P0 mouse pups. We found that the absence of PrP(C) profoundly affected the firing properties of cultured hippocampal neurons in the presence of synaptic blockers...
2016: Frontiers in Cellular Neuroscience
Zhe Zhao, Kang Zhang, Xiaoyan Liu, Haitao Yan, Xiaoyun Ma, Shuzhuo Zhang, Jianquan Zheng, Liyun Wang, Xiaoli Wei
The striatum is the most prominent nucleus in the basal ganglia and plays an important role in motor movement regulation. The cholinergic interneurons (ChIs) in striatum are involved in the motion regulation by releasing acetylcholine (ACh) and modulating the output of striatal projection neurons. Here, we report that muscarinic ACh receptor (M receptor) agonists, ACh and Oxotremorine (OXO-M), decreased the firing frequency of ChIs by blocking the hyperpolarization-activated cyclic nucleotide-gated (HCN) channels...
2016: Frontiers in Cellular Neuroscience
Susanne Thon, Eckhard Schulz, Jana Kusch, Klaus Benndorf
Hyperpolarization-activated cyclic nucleotide-modulated (HCN) channels are tetrameric proteins that evoke electrical rhythmicity in specialized neurons and cardiomyocytes. The channels are activated by hyperpolarizing voltage but are also receptors for the intracellular ligand adenosine-3',5'-cyclic monophosphate (cAMP) that enhances activation but is unable to activate the channels alone. Using fcAMP, a fluorescent derivative of cAMP, we analyzed the effect of ligand binding on HCN2 channels not preactivated by voltage...
December 1, 2015: Biophysical Journal
Konstantin Wemhöner, Tatyana Kanyshkova, Nicole Silbernagel, Juncal Fernandez-Orth, Stefan Bittner, Aytug K Kiper, Susanne Rinné, Michael F Netter, Sven G Meuth, Thomas Budde, Niels Decher
Rats of the Wistar Albino Glaxo/Rij (WAG/Rij) strain show symptoms resembling human absence epilepsy. Thalamocortical neurons of WAG/Rij rats are characterized by an increased HCN1 expression, a negative shift in I h activation curve, and an altered responsiveness of I h to cAMP. We cloned HCN1 channels from rat thalamic cDNA libraries of the WAG/Rij strain and found an N-terminal deletion of 37 amino acids. In addition, WAG-HCN1 has a stretch of six amino acids, directly following the deletion, where the wild-type sequence (GNSVCF) is changed to a polyserine motif...
2015: Frontiers in Molecular Neuroscience
Hannah A DeBerg, Peter S Brzovic, Galen E Flynn, William N Zagotta, Stefan Stoll
Hyperpolarization-activated cyclic nucleotide-gated (HCN) ion channels play an important role in regulating electrical activity in the heart and brain. They are gated by the binding of cyclic nucleotides to a conserved, intracellular cyclic nucleotide-binding domain (CNBD), which is connected to the channel pore by a C-linker region. Binding of cyclic nucleotides increases the rate and extent of channel activation and shifts it to less hyperpolarized voltages. We probed the allosteric mechanism of different cyclic nucleotides on the CNBD and on channel gating...
January 1, 2016: Journal of Biological Chemistry
Pan Luo, Xiaoxue Zhang, Yun Lu, Cheng Chen, Changjun Li, Mei Zhou, Qing Lu, Xulin Xu, Guanxin Shen, Lianjun Guo
Chronic cerebral hypoperfusion (CCH) causes cognitive impairments and increases the risk of Alzheimer's disease (AD) and vascular dementia (VD) through several biologically plausible pathways, yet the underlying neurobiological mechanisms are still poorly understood. In this study, we investigated whether fluoxetine, a selective serotonin reuptake inhibitor (SSRI), could play a neuroprotective role against chronic cerebral hypoperfusion injury and to clarify underlying mechanisms of its efficacy. Rats were subjected to permanent bilateral occlusion of the common carotid arteries (two-vessel occlusion, 2VO)...
January 2016: Pharmacology, Biochemistry, and Behavior
Masayuki Itoh, Keiko Ishihara, Noriyuki Nakashima, Makoto Takano
Expression of hyperpolarization-activated cyclic nucleotide-gated channels (HCN1-4) on distal dendrites of neurons is suggested to modify synaptic integration in the central nervous system. However, the mechanisms of dendritic localization are not fully understood. Recent studies have revealed that S-palmitoylation plays an important role in the enrichment of various molecules at the postsynaptic membrane. Thus, we performed an acyl-biotinyl exchange assay, and found that HCN1, HCN2, and HCN4, but not HCN3, were S-palmitoylated in HEK293 cells...
May 2016: Journal of Physiological Sciences: JPS
Robert J Heuermann, Thomas C Jaramillo, Shui-Wang Ying, Benjamin A Suter, Kyle A Lyman, Ye Han, Alan S Lewis, Thomas G Hampton, Gordon M G Shepherd, Peter A Goldstein, Dane M Chetkovich
Absence seizures occur in several types of human epilepsy and result from widespread, synchronous feedback between the cortex and thalamus that produces brief episodes of loss of consciousness. Genetic rodent models have been invaluable for investigating the pathophysiological basis of these seizures. Here, we identify tetratricopeptide-containing Rab8b-interacting protein (TRIP8b) knockout mice as a new model of absence epilepsy, featuring spontaneous spike-wave discharges on electroencephalography (EEG) that are the electrographic hallmark of absence seizures...
January 2016: Neurobiology of Disease
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