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Rayi PR, Koyavski L, Chakraborty D, Bagrov A, Kaphzan H. α1-Na/K-ATPase inhibition rescues aberrant dendritic calcium dynamics and memory deficits in the hippocampus of an Angelman syndrome mouse model. Prog Neurobiol 2019; 182:101676. [DOI: 10.1016/j.pneurobio.2019.101676] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2019] [Revised: 07/08/2019] [Accepted: 07/31/2019] [Indexed: 12/23/2022]
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2
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Heinzen EL, Arzimanoglou A, Brashear A, Clapcote SJ, Gurrieri F, Goldstein DB, Jóhannesson SH, Mikati MA, Neville B, Nicole S, Ozelius LJ, Poulsen H, Schyns T, Sweadner KJ, van den Maagdenberg A, Vilsen B. Distinct neurological disorders with ATP1A3 mutations. Lancet Neurol 2014; 13:503-14. [PMID: 24739246 DOI: 10.1016/s1474-4422(14)70011-0] [Citation(s) in RCA: 179] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Genetic research has shown that mutations that modify the protein-coding sequence of ATP1A3, the gene encoding the α3 subunit of Na(+)/K(+)-ATPase, cause both rapid-onset dystonia parkinsonism and alternating hemiplegia of childhood. These discoveries link two clinically distinct neurological diseases to the same gene, however, ATP1A3 mutations are, with one exception, disease-specific. Although the exact mechanism of how these mutations lead to disease is still unknown, much knowledge has been gained about functional consequences of ATP1A3 mutations using a range of in-vitro and animal model systems, and the role of Na(+)/K(+)-ATPases in the brain. Researchers and clinicians are attempting to further characterise neurological manifestations associated with mutations in ATP1A3, and to build on the existing molecular knowledge to understand how specific mutations can lead to different diseases.
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Affiliation(s)
- Erin L Heinzen
- Center for Human Genome Variation, Duke University, School of Medicine, Durham, NC, USA; Department of Medicine, Section of Medical Genetics, Duke University, School of Medicine, Durham, NC, USA.
| | - Alexis Arzimanoglou
- Epilepsy, Sleep and Pediatric Neurophysiology Department, HFME, University Hospitals of Lyon, France; Centre de Recherche en Neurosciences de Lyon, Centre National de la Recherche Scientifique, UMR 5292, INSERM U1028, Lyon, France
| | - Allison Brashear
- Department of Neurology, Wake Forest School of Medicine, Winston Salem, NC, USA
| | | | - Fiorella Gurrieri
- Istituto di Genetica Medica, Università Cattolica S Cuore, Rome, Italy
| | - David B Goldstein
- Center for Human Genome Variation, Duke University, School of Medicine, Durham, NC, USA; Department of Molecular Genetics and Microbiology, Duke University, School of Medicine, Durham, NC, USA
| | | | - Mohamad A Mikati
- Division of Pediatric Neurology, Duke University, School of Medicine, Durham, NC, USA; Department of Neurobiology, Duke University, School of Medicine, Durham, NC, USA
| | - Brian Neville
- Institute of Child Health, University College London, London, UK
| | - Sophie Nicole
- Institut National de la Santé et de la Recherche Médicale, U975, Centre de Recherche de l'Institut du Cerveau et de la Moelle, Paris, France; Centre National de la Recherche Scientifique, UMR7225, Paris, France; Université Pierre et Marie Curie Paris VI, UMRS975, Paris, France
| | - Laurie J Ozelius
- Department of Genetics and Genomic Sciences and Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Hanne Poulsen
- Danish Research Institute for Translational Neuroscience, Nordic-EMBL Partnership of Molecular Medicine, Department of Molecular Biology and Genetics, Aarhus University, Aarhus, Denmark; Centre for Membrane Pumps in Cells and Disease-PUMPKIN, Danish National Research Foundation, Aarhus, Denmark
| | - Tsveta Schyns
- European Network for Research on Alternating Hemiplegia (ENRAH), Brussels, Belgium
| | | | - Arn van den Maagdenberg
- Department of Human Genetics and Department of Neurology, Leiden University Medical Centre, Leiden, Netherlands
| | - Bente Vilsen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
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3
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McLean WJ, Smith KA, Glowatzki E, Pyott SJ. Distribution of the Na,K-ATPase alpha subunit in the rat spiral ganglion and organ of corti. J Assoc Res Otolaryngol 2008; 10:37-49. [PMID: 19082858 DOI: 10.1007/s10162-008-0152-9] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2008] [Accepted: 11/20/2008] [Indexed: 12/29/2022] Open
Abstract
Processing of sound in the cochlea involves both afferent and efferent innervation. The Na,K-ATPase (NKA) is essential for cells that maintain hyperpolarized membrane potentials and sodium and potassium concentration gradients. Heterogeneity of NKA subunit expression is one mechanism that tailors physiology to particular cellular demands. Therefore, to provide insight into molecular differences that distinguish the various innervation pathways in the cochlea, we performed a variety of double labeling experiments with antibodies against three of the alpha isoforms of the NKA (NKA alpha 1-3) and markers identifying particular subsets of neurons or supporting cells in whole mount preparations of the organ of Corti and spiral ganglion. We found that the NKA alpha 3 is abundantly expressed within the membranes of the spiral ganglion somata, the type I afferent terminals contacting the inner hair cells, and the medial efferent terminals contacting the outer hair cells. We also found expression of the NKA alpha 1 in the supporting cells that neighbor the inner hair cells and express the glutamate transporter GLAST. These findings suggest that both the NKA alpha 1 and NKA alpha 3 are poised to play an essential role in the regulation of the type I afferent synapses, the medial efferent synapses, and also glutamate transport from the afferent-inner hair cell synapse.
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Affiliation(s)
- Will J McLean
- Department of Biology and Marine Biology, University of North Carolina Wilmington, 601 South College Road, Wilmington, NC 28403, USA
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4
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Richards KS, Bommert K, Szabo G, Miles R. Differential expression of Na+/K+-ATPase alpha-subunits in mouse hippocampal interneurones and pyramidal cells. J Physiol 2007; 585:491-505. [PMID: 17947306 PMCID: PMC2375485 DOI: 10.1113/jphysiol.2007.144733] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2007] [Accepted: 10/10/2007] [Indexed: 12/30/2022] Open
Abstract
The sodium pump (Na+/K+-ATPase), maintains intracellular and extracellular concentrations of sodium and potassium by catalysing ATP. Three sodium pump alpha subunits, ATP1A1, ATP1A2 and ATP1A3, are expressed in brain. We compared their role in pyramidal cells and a subset of interneurones in the subiculum. Interneurones were identified by their expression of GFP under the GAD-65 promoter. We used the sensitivity to the cardiac glycoside, ouabain, to discriminate between different alpha subunit isoforms. GFP-positive interneurones were depolarized by nanomolar doses of ouabain, but higher concentrations were needed to depolarize pyramidal cells. Comparison of pump currents in these cells revealed a current sensitive to low doses of ouabain in interneurones, while micromolar doses of ouabain were needed to suppress the pump current in subicular pyramidal cells. As predicted, nanomolar doses of ouabain increased the frequency but not the amplitudes of IPSPs in pyramidal cells. Immunostaining confirmed a differential distribution of alpha-subunits of the Na+/K+-ATPase in subicular interneurones and pyramidal cells. In conclusion, these data suggest that while ATP1A3-isoforms regulate sodium and potassium homeostasis in subicular interneurones, ATP1A1-isoforms assume this function in pyramidal cells. This differential expression of sodium pump isoforms may contribute to differences in resting membrane potential of subicular interneurones and pyramidal cells.
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Affiliation(s)
- Kathryn S Richards
- INSERM U739, CHU Pitié-Salpêtrière, 105 boulevard de l'Hôpital, 75013 Paris, France.
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Balfour RH, Trapp S. Ionic currents underlying the response of rat dorsal vagal neurones to hypoglycaemia and chemical anoxia. J Physiol 2007; 579:691-702. [PMID: 17218356 PMCID: PMC2151378 DOI: 10.1113/jphysiol.2006.126094] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
A proportion of dorsal vagal neurones (DVN) are glucosensors. These cells respond to brief hypoglycaemia either with a K(ATP) channel-mediated hyperpolarization or with depolarization owing to an as yet unknown mechanism. K(ATP) currents are observed not only during hypoglycaemia, but also in response to mitochondrial inhibition. Here we show that similarly to the observations for K(ATP) currents, both hypoglycaemia and inhibition of mitochondrial function elicited a small inward current that persisted in TTX in DVN of rat brainstem slices. Removal of glucose from the bath solution induced this inward current within 50 +/- 4 s in one subpopulation of DVN and in 279 +/- 36 s in another subpopulation. No such subpopulations were observed for the response to mitochondrial inhibition. Biophysical analysis revealed that mitochondrial inhibition or hypoglycaemia inhibited an openly rectifying K+ conductance in 25% of DVN. In the remaining cells, either an increase in conductance, with a reversal potential between -58 and +10 mV, or a parallel inward shift of the holding current was observed. This current most probably resulted from inhibition of the Na+-K+-ATPase and/or the opening of an ion channel. Recordings with electrodes containing 145 mm instead of 5 mm Cl- failed to shift the reversal potential of the inward current, indicating that a Cl- channel was not involved. In summary, glucosensing and non-glucosensing DVN appear to use common electrical pathways to respond to mitochondrial inhibition and to hypoglycaemia. We suggest that differences in glucose metabolism rather than differences in the complement of ion channels distinguish these two cell types.
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Affiliation(s)
- Robert H Balfour
- Department of Anaesthetics, Pain Medicine and Intensive Care, Chelsea & Westminster Hospital, Imperial College London, UK
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6
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Wang HY, Huang RC. Diurnal modulation of the Na+/K+-ATPase and spontaneous firing in the rat retinorecipient clock neurons. J Neurophysiol 2004; 92:2295-301. [PMID: 15381747 DOI: 10.1152/jn.00061.2004] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The ventral "core" suprachiasmatic nucleus (vSCN) neurons are the retinorecipient neurons in the mammalian circadian clock and maintain a diurnal firing rhythm in reduced preparations. We tested the possibility that daily changes in Na+/K+-ATPase accompany diurnal variation in spontaneous electrical activity. In control, bath application of 9 microM strophanthidin increased the spontaneous firing both at day and night but to different extents. In the presence of 1 mM Ni2+ to block spontaneous firing, addition of 9 microM strophanthidin, but not higher concentrations (6.5-20 mM) of external K+, induced the silenced cells to fire action potentials in a diurnal rhythm, suggesting a diurnal change in Na+/K+-ATPase activity. Consistently, voltage-clamp recordings demonstrated that the pump current blocked by 9 microM strophanthidin was approximately three times larger in daytime than nighttime and was little affected by the presence of 1 mM Ni2+. Experiments with various concentrations of strophanthidin further suggests day-night differences in maximum Na+/K+-ATPase activity, amounting to 6 pA of pump current at day and down to 3.5 pA at night, and in its half-block concentrations, changing from a daytime value of 4 microM to a nighttime value of 8 microM. Our results indicate that the vSCN neurons exhibit a diurnal rhythm in the Na+/K+-ATPase the activity of which is higher during the day when the firing rate is also higher. Mechanistically, the modulation could be accounted for in terms of changes in the maximum activity of Na+/K+-ATPase and its ability to block by strophanthidin.
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Affiliation(s)
- Han-Ying Wang
- Dept. of Physiology, Chang Gung University School of Medicine, 259 Wen-Hwa 1st Rd., Kwei-San, Tao-Yuan, Taiwan
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7
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Hu B. Functional organization of lemniscal and nonlemniscal auditory thalamus. Exp Brain Res 2003; 153:543-9. [PMID: 12937877 DOI: 10.1007/s00221-003-1611-5] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2002] [Accepted: 06/14/2003] [Indexed: 12/19/2022]
Abstract
Thalamic nuclei of the mammalian auditory system exhibit remarkable parallelism in their anatomical pathways and the patterns of synaptic signalling. This has led to the theory that lemniscal, or core thalamocortical projection, carries tonotopically organized and auditory specific information whereas the nonlemniscal thalamocortical pathway forms part of an integrative system that plays an important role in polysensory integration, temporal pattern recognition, and certain forms of learning. Recent experimental evidence derived from molecular, cellular and behavioural studies indeed supports the conjecture that lemniscal and nonlemniscal pathways are involved in distinctive auditory functions.
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Affiliation(s)
- B Hu
- Department of Clinical Neurosciences and Neuroscience Research Group, University of Calgary, 3330 Hospital Drive NW, Calgary, Alberta, T2N 4N1, Canada.
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8
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Darbon P, Tscherter A, Yvon C, Streit J. Role of the electrogenic Na/K pump in disinhibition-induced bursting in cultured spinal networks. J Neurophysiol 2003; 90:3119-29. [PMID: 12890799 DOI: 10.1152/jn.00579.2003] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Disinhibition-induced bursting activity in cultures of fetal rat spinal cord is mainly controlled by intrinsic spiking with subsequent recurrent excitation of the network through glutamate synaptic transmission, and by autoregulation of neuronal excitability. Here we investigated the contribution of the electrogenic Na/K pump to the autoregulation of excitability using extracellular recordings by multielectrode arrays (MEAs) and intracellular whole cell recordings from spinal interneurons. The blockade of the electrogenic Na/K pump by strophanthidin led to an immediate and transient increase in the burst rate together with an increase in the asynchronous background activity. Later, the burst rate decreased to initial values and the bursts became shorter and smaller. In single neurons, we observed an immediate depolarization of the membrane during the interburst intervals concomitant with the rise in burst rate. This depolarization was more pronounced during disinhibition than during control, suggesting that the pump was more active. Later a decrease in burst rate was observed and, in some neurons, a complete cessation of firing. Most of the effects of strophanthidin could be reproduced by high K+-induced depolarization. During prolonged current injections, spinal interneurons exhibited spike frequency adaptation, which remained unaffected by strophanthidin. These results suggest that the electrogenic Na/K pump is responsible for the hyperpolarization and thus for the changes in excitability during the interburst intervals, although not for the spike frequency adaptation during the bursts.
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Affiliation(s)
- P Darbon
- Institute of Physiology, University of Bern, 3012 Bern, Switzerland.
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9
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Wang XQ, Xiao AY, Sheline C, Hyrc K, Yang A, Goldberg MP, Choi DW, Yu SP. Apoptotic insults impair Na+, K+-ATPase activity as a mechanism of neuronal death mediated by concurrent ATP deficiency and oxidant stress. J Cell Sci 2003; 116:2099-110. [PMID: 12679386 DOI: 10.1242/jcs.00420] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
The Na+, K+-ATPase (Na+, K+-pump) plays critical roles in maintaining ion homeostasis. Blocking the Na+, K+-pump may lead to apoptosis. By contrast, whether an apoptotic insult may affect the Na+, K+-pump activity is largely undefined. In cultured cortical neurons, the Na+, K+-pump activity measured as a membrane current Ipump was time-dependently suppressed by apoptotic insults including serum deprivation, staurosporine, and C2-ceramide, concomitant with depletion of intracellular ATP and production of reactive oxygen species. Signifying a putative relationship among these events, Ipump was highly sensitive to changes in ATP and reactive oxygen species levels. Moreover, the apoptosis-associated Na+, K+-pump failure and serum deprivation-induced neuronal death were antagonized by pyruvate and succinate in ATP- and reactive-oxygen-species-dependent manners. We suggest that failure of the Na+, K+-pump as a result of a combination of energy deficiency and production of reactive oxygen species is a common event in the apoptotic cascade; preserving the pump activity provides a neuroprotective strategy in certain pathological conditions.
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Affiliation(s)
- Xue Qing Wang
- Center for the Study of Nervous System Injury and Department of Neurology, Washington University School of Medicine, St Louis, MO 63110, USA
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10
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Vaillend C, Mason SE, Cuttle MF, Alger BE. Mechanisms of neuronal hyperexcitability caused by partial inhibition of Na+-K+-ATPases in the rat CA1 hippocampal region. J Neurophysiol 2002; 88:2963-78. [PMID: 12466422 DOI: 10.1152/jn.00244.2002] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Extra- and intracellular records were made from rat acute hippocampal slices to examine the effects of partial inhibition of Na(+)-K(+)-ATPases (Na(+)-K(+) pumps) on neuronal hyperexcitability. Bath application of the low-affinity cardiac glycoside, dihydroouabain (DHO), reversibly induced interictal-like epileptiform bursting activity in the CA1 region. Burst-firing was correlated with inhibition of the pumps, which was assayed by changes in [K(+)](o) uptake rates measured with K(+)-ion-sensitive microelectrodes. Large increases in resting [K(+)](o) did not occur. DHO induced a transient depolarization (5-6 mV) followed by a long-lasting hyperpolarization (approximately 6 mV) in CA1 pyramidal neurons, which was accompanied by a 30% decrease in resting input resistance. Block of an electrogenic pump current could explain the depolarization but not the hyperpolarization of the membrane. Increasing [K(+)](o) from 3 to 5.5 mM minimized these transient shifts in passive membrane properties without preventing DHO-induced hyperexcitability. DHO decreased synaptic transmission, but increased the coupling between excitatory postsynaptic potentials and spike firing (E-S coupling). Monosynaptic inhibitory postsynaptic potential (IPSP) amplitudes declined to approximately 25% of control at the peak of bursting activity; however, miniature TTX-resistant inhibitory postsynaptic current amplitudes were unaffected. DHO also reduced the initial slope of the intracellular excitatory postsynaptic potential (EPSP) to approximately 40% of control. The conductances of pharmacologically isolated IPSPs and EPSPs in high-Ca/high-Mg-containing saline were also reduced by DHO by approximately 50%. The extracellular fiber volley amplitude was reduced by 15-20%, suggesting that the decrease in neurotransmission was partly due to a reduction in presynaptic fiber excitability. DHO enhanced a late depolarizing potential that was superimposed on the EPSP and could obscure it. This potential was not blocked by antagonists of NMDA receptors, and blockade of NMDA, mGlu, or GABA(A) receptors did not affect burst firing. The late depolarizing component enabled the pyramidal cells to reach spike threshold without changing the actual voltage threshold for firing. We conclude that reduced GABAergic potentials and enhanced E-S coupling are the primary mechanisms underlying the hyperexcitability associated with impaired Na(+)-K(+) pump activity.
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Affiliation(s)
- Cyrille Vaillend
- Department of Physiology, University of Maryland School of Medicine, Baltimore, Maryland 21201, USA
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Quinn K, Guibert C, Beech DJ. Sodium-potassium-ATPase electrogenicity in cerebral precapillary arterioles. Am J Physiol Heart Circ Physiol 2000; 279:H351-60. [PMID: 10899075 DOI: 10.1152/ajpheart.2000.279.1.h351] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Electrogenicity of the Na(+)/K(+) pump has the capability to generate a large negative membrane potential independently of ion-channel current. The high background membrane resistance of arterioles may make them susceptible to such an effect. Pump current was detected by patch-clamp recording from smooth muscle cells in fragments of arterioles (diameter 24-58 microm) isolated from pial membrane of rabbit cerebral cortex. The current was 20 pA at -60 mV, and the extrapolated zero current potential was -160 mV. Two methods of estimating the effect of pump electrogenicity on resting potential indicated an average contribution of -35 mV. In 20% of the recordings, block of inward rectifier K(+) channels by 10-100 microM Ba(2+) led to a small depolarization, but hyperpolarization was a more common response. Ba(2+) also inhibited depolarization evoked by 20 mM K(+). In arterioles within intact pial membrane, Ba(2+) failed to evoke constriction but inhibited K(+)-induced constriction. The data suggest that cerebral arterioles are vulnerable to the hyperpolarizing effect of the Na(+)/K(+) pump, excessive effects of which are prevented by depolarizing inward rectifier K(+) current
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Affiliation(s)
- K Quinn
- School of Biomedical Sciences, University of Leeds, Leeds LS2 9JT, United Kingdom
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12
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Dobolyi A, Reichart A, Szikra T, Nyitrai G, Kékesi KA, Juhász G. Sustained depolarisation induces changes in the extracellular concentrations of purine and pyrimidine nucleosides in the rat thalamus. Neurochem Int 2000; 37:71-9. [PMID: 10781847 DOI: 10.1016/s0197-0186(99)00162-x] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
ATP and adenosine are well-known neuroactive compounds. Other nucleotides and nucleosides may also be involved in different brain functions. This paper reports on extracellular concentrations of nucleobases and nucleosides (uracil, hypoxanthine, xanthine, uridine, 2'-deoxycytidine, 2'-deoxyuridine, inosine, guanosine, thymidine, adenosine) in response to sustained depolarisation, using in vivo brain microdialysis technique in the rat thalamus. High-potassium solution, the glutamate agonist kainate, and the Na(+)/K(+) ATPase blocker ouabain were applied in the perfusate of microdialysis probes and induced release of various purine and pyrimidine nucleosides. All three types of depolarisation increased the level of hypoxanthine, uridine, inosine, guanosine and adenosine. The levels of measured deoxynucleosides (2'-deoxycytidine, 2'-deoxyuridine and thymidine) decreased or did not change, depending on the type of depolarisation. Kainate-induced changes were TTX insensitive, and ouabain-induced changes for inosine, guanosine, 2'-deoxycytidine and 2'-deoxyuridine were TTX sensitive. In contrast, TTX application without depolarisation decreased the extracellular concentrations of hypoxanthine, uridine, inosine, guanosine and adenosine. Our data suggest that various nucleosides may be released from cells exposed to excessive activity and, thus, support several different lines of research concerning the regulatory roles of nucleosides.
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Affiliation(s)
- A Dobolyi
- Research Group of Neurobiology MTA-ELTE, Hungarian Academy of Sciences, Eötvös Loránd University, H-1088, Budapest, Hungary
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Senatorov VV, Stys PK, Hu B. Regulation of Na+,K+-ATPase by persistent sodium accumulation in adult rat thalamic neurones. J Physiol 2000; 525 Pt 2:343-53. [PMID: 10835038 PMCID: PMC2269957 DOI: 10.1111/j.1469-7793.2000.00343.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
The present study investigated the regulatory mechanism of the Na+, K+-ATPase and the level of internal Na+ and Ca2+ in response to persistent Na+ influx in acutely dissociated rat thalamic neurones. Whole-cell patch-clamp recordings and Na+ imaging revealed a stable [Na+]i and low background pump activity. Exposure to veratridine (50 microM) for 1 h resulted in a progressive rise in [Na+]i (DeltaFNa = 64 +/-22%) and [Ca2+]i (DeltaFCa = 44 +/- 14%) over 3 h. Increases in [Na+]i and [Ca2+]i were also observed during neuronal exposure to the Na+ ionophore monensin (50 microM). Subcellular confocal immunofluorescence quantification of alpha3 catalytic Na+-K+ pump subunits showed that a veratridine-induced rise in [Na+]i was accompanied by a significant increase in pump density in both membrane and cytoplasmic compartments, by 39 and 54%, respectively. Similar results were also obtained in experiments when neurones were treated with monensin. A fluorescent 9-anthroylouabain binding assay detected a 60 and 110% increase in phosphorylated (active) pumps after veratridine and monensin exposure, respectively. During the entire experiment, application of ouabain or veratridine alone induced little cell swelling and death, but pump inhibition in cells pre-loaded with Na+ led to rapid cell swelling and necrosis. The above results indicate that a persistent influx of Na+ may trigger rapid enhancement of pump synthesis, membrane redistribution and functional activity. However, these compensatory mechanisms failed to prevent persistent Na+ accumulation.
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Affiliation(s)
- V V Senatorov
- Loeb Health Research Institute, Ottawa Hospital, University of Ottawa, Ottawa, Ontario, Canada K1Y 4E9.
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14
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Ross ST, Soltesz I. Selective depolarization of interneurons in the early posttraumatic dentate gyrus: involvement of the Na(+)/K(+)-ATPase. J Neurophysiol 2000; 83:2916-30. [PMID: 10805688 DOI: 10.1152/jn.2000.83.5.2916] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Interneurons innervating dentate granule cells are potent regulators of the entorhino-hippocampal interplay. Traumatic brain injury, a leading cause of death and disability among young adults, is frequently associated with rapid neuropathological changes, seizures, and short-term memory deficits both in humans and experimental animals, indicating significant posttraumatic perturbations of hippocampal circuits. To determine the pathophysiological alterations that affect the posttraumatic functions of dentate neuronal networks within the important early (hours to days) posttraumatic period, whole cell patch-clamp recordings were performed from granule cells and interneurons situated in the granule cell layer of the dentate gyrus of head-injured and age-matched, sham-operated control rats. The data show that a single pressure wave-transient delivered to the neocortex of rats (mimicking moderate concussive head trauma) resulted in a characteristic ( approximately 10 mV), transient (<4 days), selective depolarizing shift in the resting membrane potential of dentate interneurons, but not in neighboring granule cells. The depolarization was not associated with significant changes in action potential characteristics or input resistance, and persisted in the presence of antagonists of ionotropic and metabotropic glutamate, and GABA(A) and muscarinic receptors, as well as blockers of voltage-dependent sodium channels and of the h-current. The differential action of the cardiac glycosides oubain and stophanthidin on interneurons from control versus head-injured rats indicated that the depolarization of interneurons was related to the trauma-induced decrease in the activity of the electrogenic Na(+)/K(+)-ATPase. In contrast, the Na(+)/K(+)-ATPase activity in granule cells did not change. Intracellular injection of Na(+), Ca(2+)-chelator and ATP, as well as ATP alone, abolished the difference between the resting membrane potentials of control and injured interneurons. The selective posttraumatic depolarization increased spontaneous firing in interneurons, enhanced the frequency and amplitude of spontaneous inhibitory postsynaptic currents (IPSCs) in granule cells, and augmented the efficacy of depolarizing inputs to discharge interneurons. These results demonstrate that mechanical neurotrauma delivered to a remote site has highly selective effects on different cell types even within the same cell layer, and that the electrogenic Na(+)-pump plays a role in setting the excitability of hippocampal interneuronal networks after injury.
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Affiliation(s)
- S T Ross
- Department of Anatomy and Neurobiology, University of California, Irvine, California 92697-1280, USA
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15
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Inoue M, Fujishiro N, Imanaga I. Na+ pump inhibition and non-selective cation channel activation by cyanide and anoxia in guinea-pig chromaffin cells. J Physiol 1999; 519 Pt 2:385-96. [PMID: 10457057 PMCID: PMC2269519 DOI: 10.1111/j.1469-7793.1999.0385m.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
1. Hypoxia and metabolic inhibition with cyanide (CN) evoke catecholamine secretion in adrenal chromaffin cells through depolarization. We elucidated mechanisms for a CN- or anoxia-induced inward (depolarization) current, using the perforated patch method. 2. Bath application of Ba2+ induced a dose-dependent inhibition of a muscarine-induced current (IMUS) and part of the CN-induced current (ICN) with an IC50 (concentration responsible for 50 % inhibition) of 1.3 mM. The Ba2+-sensitive component was estimated to comprise 58 % of the total ICN. 3. The Ba2+-resistant component of ICN tended to increase with shifts of membrane potential from -40 to 40 mV and was markedly suppressed by exposure to a K+-free solution or 200 microM ouabain, indicating that the majority of the Ba2+-resistant component of ICN is due to suppression of the Na+ pump current (Ipump). 4. The non-Ipump component of ICN diminished progressively in K+-free solution. Substitution of glucose for sucrose in a K+-free CN solution further diminished the CN potency to produce the non-Ipump component. 5. The I-V relationship for the non-Ipump component of ICN had a reversal potential of -3 and -47 mV at 147 and 5.5 mM Na+, respectively, and showed an outward rectification, indicating that the non-Ipump component of ICN is due to activation of non-selective cation channels. 6. Exposure to anoxia induced a current with an amplitude comparable to that of ICN, and the anoxia-induced current apparently occluded development of ICN. The anoxia-induced current diminished by ca 60 % in the absence of K+ and reversed polarity at 5 mV under K+-free conditions. 7. It is concluded that exposure to CN and to anoxia induces suppression of the Na+ pump and activation of non-selective cation channels, probably due to an ATP decrease resulting mainly from consumption by the Na+ pump.
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Affiliation(s)
- M Inoue
- Department of Physiology, School of Medicine, Fukuoka University, Fukuoka 814 0180, Japan.
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Abstract
Steady-state Na+/K+ pump current (Ip) in isolated adult rat dorsal root ganglia neurons was studied to determine if the plasma membrane Na+/K+ pump activity is uniform across the population of dorsal root ganglia neurons. Cells were voltage-clamped at -40 mV and holding current (Ih) was recorded using whole-cell patch-clamp techniques under conditions that stimulate the Na+/K+ pump (60 mM intracellular Na+ and 5.4 mM extracellular K+). Ip was defined as the 1 mM ouabain-sensitive fraction of Ih. Data suggest the existence of three subpopulations of dorsal root ganglia neurons having mean steady-state Ip densities of 1.6+/-0.1, 3.8+/-0.2 and 7.5+/-0.4 pA/pF. Neurons with small Ip had an average soma perimeter of 95+/-3 microm, while neurons with medium and large Ip density had significantly larger soma sizes (131+/-8 and 141+/-7 microm, respectively). Neurons with a large Ip density had a significantly lower specific membrane resistance (Rm; mean 4.0+/-0.3 kohm x cm2) than neurons with medium or small Ip density (19+/-6 and 31+/-6 kohm x cm2, respectively). Regardless of these differences, in all groups of neurons Ip had a low sensitivity to ouabain (Ip half inhibition by ouabain was observed at 80-110 microM). These data suggest that the Na+/K+ pump site density and/or its activity is not uniform throughout the dorsal root ganglia neuron population; however, this non-uniformity does not appear to relate to the functional expression of the different alpha isoforms of the Na+/K+ pump. The major functional Na+/K+ pump in the dorsal root ganglia neuron plasma membrane appeared to be the low ouabain affinity (alpha1) isoform.
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Affiliation(s)
- M Dobretsov
- Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205, USA
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Bartlett EL, Smith PH. Anatomic, intrinsic, and synaptic properties of dorsal and ventral division neurons in rat medial geniculate body. J Neurophysiol 1999; 81:1999-2016. [PMID: 10322042 DOI: 10.1152/jn.1999.81.5.1999] [Citation(s) in RCA: 125] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Anatomic, intrinsic, and synaptic properties of dorsal and ventral division neurons in rat medial geniculate body. Presently little is known about what basic synaptic and cellular mechanisms are employed by thalamocortical neurons in the two main divisions of the auditory thalamus to elicit their distinct responses to sound. Using intracellular recording and labeling methods, we characterized anatomic features, membrane properties, and synaptic inputs of thalamocortical neurons in the dorsal (MGD) and ventral (MGV) divisions in brain slices of rat medial geniculate body. Quantitative analysis of dendritic morphology demonstrated that tufted neurons in both divisions had shorter dendrites, smaller dendritic tree areas, more profuse branching, and a greater dendritic polarization compared with stellate neurons, which were only found in MGD. Tufted neuron dendritic polarization was not as strong or consistent as earlier Golgi studies suggested. MGV and MGD cells had similar intrinsic properties except for an increased prevalence of a depolarizing sag potential in MGV neurons. The sag was the only intrinsic property correlated with cell morphology, seen only in tufted neurons in either division. Many MGV and MGD neurons received excitatory and inhibitory inferior colliculus (IC) inputs (designated IN/EX or EX/IN depending on excitation/inhibition sequence). However, a significant number only received excitatory inputs (EX/O) and a few only inhibitory (IN/O). Both MGV and MGD cells displayed similar proportions of response combinations, but suprathreshold EX/O responses only were observed in tufted neurons. Excitatory and inhibitory postsynaptic potentials (EPSPs and IPSPs) had multiple distinguishable amplitude levels implying convergence. Excitatory inputs activated alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) receptors the relative contributions of which were variable. For IN/EX cells with suprathreshold inputs, first-spike timing was independent of membrane potential unlike that of EX/O cells. Stimulation of corticothalamic (CT) and thalamic reticular nucleus (TRN) axons evoked a GABAA IPSP, EPSP, GABAB IPSP sequence in most neurons with both morphologies in both divisions. TRN IPSPs and CT EPSPs were graded in amplitude, again suggesting convergence. CT inputs activated AMPA and NMDA receptors. The NMDA component of both IC and CT inputs had an unusual voltage dependence with a detectable DL-2-amino-5-phosphonovaleric acid-sensitive component even below -70 mV. First-spike latencies of CT evoked action potentials were sensitive to membrane potential regardless of whether the TRN IPSP was present. Overall, our in vitro data indicate that reported regional differences in the in vivo responses of MGV and MGD cells to auditory stimuli are not well correlated with major differences in intrinsic membrane features or synaptic responses between cell types.
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Affiliation(s)
- E L Bartlett
- Department of Anatomy and The Neuroscience Training Program, University of Wisconsin, Madison, Wisconsin 53706-1532, USA
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Shen KZ, Johnson SW. Sodium pump evokes high density pump currents in rat midbrain dopamine neurons. J Physiol 1998; 512 ( Pt 2):449-57. [PMID: 9763634 PMCID: PMC2231210 DOI: 10.1111/j.1469-7793.1998.449be.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
1. Patch pipettes contained various concentrations of Na+ ([Na+]pip) in order to record strophanthidin-sensitive currents under voltage clamp in dopamine neurons in slices of rat substantia nigra and ventral tegmental area. 2. When [Na+]pip was 40 mM and the external K+ concentration ([K+]o) was 2.5 mM, strophanthidin (10 microM) evoked 461 +/- 121 pA of inward current. This effect was concentration dependent, with an EC50 of 7.1 +/- 2.6 microM. At potentials of -60 to -120 mV, strophanthidin-induced currents were not associated with significant changes in chord conductance. 3. Strophanthidin (10 microM) evoked 234 +/- 43 pA of inward current when [Na+]pip was 0.6 mM, and 513 +/- 77 pA when [Na+]pip was 80 mM. Despite higher pump currents with greater [Na+]pip, the strophanthidin EC50 was not significantly different for any of six different [Na+]pip. 4. Sodium pump currents were half-maximal when the [Na+]pip was about 1.3 mM. Maximum pump current was estimated at 830 pA (29 microA cm-2) at concentrations of intracellular Na+ that were assumed to be saturating (50-100 mM). 5. Strophanthidin currents were smaller in a reduced [K+]o (EC50 = 0.2 mM). 6. These data show that intracellular Na+ loading evokes relatively large pump currents. Our results are consistent with the physiological role of the sodium pump in burst firing in midbrain dopamine neurons
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Affiliation(s)
- K Z Shen
- Departments of Physiology and Pharmacology, Oregon Health Sciences University, Portland, OR 97201, USA
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Senatorov VV, Hu B. Differential Na(+)-K(+)-ATPase activity in rat lemniscal and non-lemniscal auditory thalami. J Physiol 1997; 502 ( Pt 2):387-95. [PMID: 9263918 PMCID: PMC1159557 DOI: 10.1111/j.1469-7793.1997.387bk.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
1. Using whole-cell recording and confocal immunofluorescent microscopy, we have investigated the differential electrogenic activity, subunit expression and subcellular distribution of the Na(+)-K(+)-ATPase in the lemniscal (ventral) and non-lemniscal (dorsal) pathways of the rat medial geniculate body (MGB) in vitro. 2. Bath application of Na(+)-K(+)-ATPase inhibitors strophanthidin or dihydro-ouabain produced a transient, dose-dependent inward current or membrane depolarization which were significantly larger in dorsal MGB neurones than in ventral cells (45.9 +/- 6.45 vs. 24.3 +/- 4.1 pA; P < 0.05). Electrophysiological and morphometric measurements showed that the dorsal MGB neurones had a significantly lower input conductance and a smaller somata than their ventral counterparts. The level of the resting membrane potential also differed by about 6 mV between the two cell populations, with the dorsal cells being more hyperpolarized (-74.2 +/- 0.6 vs. -67.7 +/- 1.3 mV; P < 0.001). 3. Incubation of enzymatically dissociated MGB neurones with fluorescent monoclonal antibodies against alpha 1-alpha 3 isoforms of Na(+)-K(+)-ATPase showed that both dorsal and ventral cells expressed primarily alpha 3 subunits. Confocal laser scanning revealed, however, that the mean pixel density of alpha 3 fluorescent antibodies in the plasma membrane domain, but not in the cytoplasmic compartment, was about 40% higher in dorsal neurones than in the ventral cells (29.7 +/- 4.7 vs. 16.9 +/- 2.3 grey shadow per pixel; P < 0.05). 4. The above results suggest that the electrogenic activity of the Na(+)-K(+)-ATPase is differentially regulated between lemniscal and non-lemniscal auditory thalami through a mechanism that probably involves differential pump densities in the cell membrane.
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Affiliation(s)
- V V Senatorov
- Loeb Medical Research Institute, Ottawa Civic Hospital, University of Ottawa, Ontario, Canada
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