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Hosford PS, Wells JA, Nizari S, Christie IN, Theparambil SM, Castro PA, Hadjihambi A, Barros LF, Ruminot I, Lythgoe MF, Gourine AV. CO 2 signaling mediates neurovascular coupling in the cerebral cortex. Nat Commun 2022; 13:2125. [PMID: 35440557 PMCID: PMC9019094 DOI: 10.1038/s41467-022-29622-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Accepted: 03/23/2022] [Indexed: 11/24/2022] Open
Abstract
Neurovascular coupling is a fundamental brain mechanism that regulates local cerebral blood flow (CBF) in response to changes in neuronal activity. Functional imaging techniques are commonly used to record these changes in CBF as a proxy of neuronal activity to study the human brain. However, the mechanisms of neurovascular coupling remain incompletely understood. Here we show in experimental animal models (laboratory rats and mice) that the neuronal activity-dependent increases in local CBF in the somatosensory cortex are prevented by saturation of the CO2-sensitive vasodilatory brain mechanism with surplus of exogenous CO2 or disruption of brain CO2/HCO3- transport by genetic knockdown of electrogenic sodium-bicarbonate cotransporter 1 (NBCe1) expression in astrocytes. A systematic review of the literature data shows that CO2 and increased neuronal activity recruit the same vasodilatory signaling pathways. These results and analysis suggest that CO2 mediates signaling between neurons and the cerebral vasculature to regulate brain blood flow in accord with changes in the neuronal activity.
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Affiliation(s)
- Patrick S Hosford
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK.
| | - Jack A Wells
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Shereen Nizari
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Isabel N Christie
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Shefeeq M Theparambil
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - Pablo A Castro
- Centro de Estudios Científicos (CECs) & Universidad San Sebastián, Valdivia, Chile
- Universidad Austral de Chile, Valdivia, Chile
| | - Anna Hadjihambi
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK
| | - L Felipe Barros
- Centro de Estudios Científicos (CECs) & Universidad San Sebastián, Valdivia, Chile
| | - Iván Ruminot
- Centro de Estudios Científicos (CECs) & Universidad San Sebastián, Valdivia, Chile.
| | - Mark F Lythgoe
- UCL Centre for Advanced Biomedical Imaging, Division of Medicine, University College London, London, UK
| | - Alexander V Gourine
- Centre for Cardiovascular and Metabolic Neuroscience, Neuroscience, Physiology and Pharmacology, University College London, London, UK.
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Carrasco MA, Castro PA, Sepulveda FJ, Cuevas M, Tapia JC, Izaurieta P, van Zundert B, Aguayo LG. Anti-homeostatic synaptic plasticity of glycine receptor function after chronic strychnine in developing cultured mouse spinal neurons. J Neurochem 2006; 100:1143-54. [PMID: 17217420 DOI: 10.1111/j.1471-4159.2006.04306.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
In this study, we describe a novel form of anti-homeostatic plasticity produced after culturing spinal neurons with strychnine, but not bicuculline or 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). Strychnine caused a large increase in network excitability, detected as spontaneous synaptic currents and calcium transients. The calcium transients were associated with action potential firing and activation of gamma-aminobutyric acid (GABA(A)) and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors as they were blocked by tetrodotoxin (TTX), bicuculline, and CNQX. After chronic blockade of glycine receptors (GlyRs), the frequency of synaptic transmission showed a significant enhancement demonstrating the phenomenon of anti-homeostatic plasticity. Spontaneous inhibitory glycinergic currents in treated cells showed a fourfold increase in frequency (from 0.55 to 2.4 Hz) and a 184% increase in average peak amplitude compared with control. Furthermore, the augmentation in excitability accelerated the decay time constant of miniature inhibitory post-synaptic currents. Strychnine caused an increase in GlyR current density, without changes in the apparent affinity. These findings support the idea of a post-synaptic action that partly explains the increase in synaptic transmission. This phenomenon of synaptic plasticity was blocked by TTX, an antibody against brain-derived neurotrophic factor (BDNF) and K252a suggesting the involvement of the neuronal activity-dependent BDNF-TrkB signaling pathway. These results show that the properties of GlyRs are regulated by the degree of neuronal activity in the developing network.
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Affiliation(s)
- M A Carrasco
- Laboratory of Neurophysiology, Department of Physiology, University of Concepción, Concepción, Chile
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Baraban SC, Taylor MR, Castro PA, Baier H. Pentylenetetrazole induced changes in zebrafish behavior, neural activity and c-fos expression. Neuroscience 2005; 131:759-68. [PMID: 15730879 DOI: 10.1016/j.neuroscience.2004.11.031] [Citation(s) in RCA: 438] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/04/2004] [Indexed: 11/29/2022]
Abstract
Rodent seizure models have significantly contributed to our basic understanding of epilepsy. However, medically intractable forms of epilepsy persist and the fundamental mechanisms underlying this disease remain unclear. Here we show that seizures can be elicited in a simple vertebrate system e.g. zebrafish larvae (Danio rerio). Exposure to a common convulsant agent (pentylenetetrazole, PTZ) induced a stereotyped and concentration-dependent sequence of behavioral changes culminating in clonus-like convulsions. Extracellular recordings from fish optic tectum revealed ictal and interictal-like electrographic discharges after application of PTZ, which could be blocked by tetrodotoxin or glutamate receptor antagonists. Epileptiform discharges were suppressed by commonly used antiepileptic drugs, valproate and diazepam, in a concentration-dependent manner. Up-regulation of c-fos expression was also observed in CNS structures of zebrafish exposed to PTZ. Taken together, these results demonstrate that chemically-induced seizures in zebrafish exhibit behavioral, electrographic, and molecular changes that would be expected from a rodent seizure model. Therefore, zebrafish larvae represent a powerful new system to study the underlying basis of seizure generation, epilepsy and epileptogenesis.
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Affiliation(s)
- S C Baraban
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, Box 0520, 503 Parnassus Avenue, San Francisco, CA 94143, USA.
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Katemann BB, Inchauspe CG, Castro PA, Schulte A, Calvo EJ, Schuhmann W. Precursor sites for localised corrosion on lacquered tinplates visualised by means of alternating current scanning electrochemical microscopy. Electrochim Acta 2003. [DOI: 10.1016/s0013-4686(02)00822-8] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
Cortical malformations resulting from aberrant brain development can be associated with mental retardation, dyslexia, and intractable forms of epilepsy. Despite emerging interest in the pathology and etiology of cortical malformations, little is known about the phenotype of cells within these lesions. In utero exposure to the DNA methylating agent methylazoxymethanol acetate (MAM) during a critical stage in neurodevelopment results in animals with distinct clusters of displaced neurons in hippocampus, i.e. nodular heterotopia. Here we examined the molecular and electrophysiological properties of cells within hippocampal heterotopia using rats exposed to MAM during gestation. Molecular analysis revealed that heterotopic cells do not express mRNA markers normally found in hippocampal pyramidal cells or dentate granule cells (SCIP, Math-2, Prox-1, neuropilin-2). In contrast, Id-2 mRNA, normally abundant in Layer II-III supragranular neocortical neurons but not in CA1 pyramidal neurons, was prominently expressed in hippocampal heterotopia. Current-clamp analysis of the firing properties of heterotopic neurons revealed a striking similarity with supragranular cortical neurons. In particular, both cells were characterized by small hyperpolarizing 'sag' potentials, high input resistance values, slow spike-train afterhyperpolarizations, and the absence of a depolarizing afterpotential. Normotopic CA1 pyramidal neurons (e.g. pyramidal cells with normal lamination adjacent to a heterotopia) in the MAM brain exhibited molecular and electrophysiological properties that were nearly identical to those of age-matched CA1 pyramidal neurons from control rats. We conclude that neuronal heterotopiae in the hippocampus of MAM-exposed rats are comprised of neurons with a Layer II-III supragranular cortex phenotype. The MAM model, therefore, may serve as a useful tool in examination of the factors influencing aberrant brain development and epilepsy.
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Affiliation(s)
- P A Castro
- Epilepsy Research Laboratory, Department of Neurological Surgery, University of California, San Francisco, Box 0520, 513 Parnassus Avenue, 94143, USA
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Castro PA, Cooper EC, Lowenstein DH, Baraban SC. Hippocampal heterotopia lack functional Kv4.2 potassium channels in the methylazoxymethanol model of cortical malformations and epilepsy. J Neurosci 2001; 21:6626-34. [PMID: 11517252 PMCID: PMC6763091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2001] [Revised: 06/11/2001] [Accepted: 06/14/2001] [Indexed: 02/21/2023] Open
Abstract
Human cortical malformations often result in severe forms of epilepsy. Although the morphological properties of cells within these malformations are well characterized, very little is known about the function of these cells. In rats, prenatal methylazoxymethanol (MAM) exposure produces distinct nodules of disorganized pyramidal-like neurons (e.g., nodular heterotopia) and loss of lamination in cortical and hippocampal structures. Hippocampal nodular heterotopias are prone to hyperexcitability and may contribute to the increased seizure susceptibility observed in these animals. Here we demonstrate that heterotopic pyramidal neurons in the hippocampus fail to express a potassium channel subunit corresponding to the fast, transient A-type current. In situ hybridization and immunohistochemical analysis revealed markedly reduced expression of Kv4.2 (A-type) channel subunits in heterotopic cell regions of the hippocampus of MAM-exposed rats. Patch-clamp recordings from visualized heterotopic neurons indicated a lack of fast, transient (I(A))-type potassium current and hyperexcitable firing. A-type currents were observed on normotopic pyramidal neurons in MAM-exposed rats and on interneurons, CA1 pyramidal neurons, and cortical layer V-VI pyramidal neurons in saline-treated control rats. Changes in A-current were not associated with an alteration in the function or expression of delayed, rectifier (Kv2.1) potassium channels on heterotopic cells. We conclude that heterotopic neurons lack functional A-type Kv4.2 potassium channels and that this abnormality could contribute to the increased excitability and decreased seizure thresholds associated with brain malformations in MAM-exposed rats.
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Affiliation(s)
- P A Castro
- Department of Neurological Surgery, The Graduate Program in Neuroscience, University of California, San Francisco, San Francisco, California 94143, USA
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Abstract
Prenatal cocaine exposure can result in neurobehavioral disturbances and structural modifications of the central nervous system. In the present study, cocaine was injected into pregnant rats and the brains of their offspring were examined at the light microscopic level. As adults, cocaine-exposed offspring exhibited subtle, but consistent, hippocampal abnormalities. In particular, the stratum pyramidale (particularly the CA1 region) was interrupted by frequent gaps in lamination, and ectopic pyramidal cells were found in stratum oriens and radiatum.
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Affiliation(s)
- S C Baraban
- Departments of Pediatrics and Neuroscience, MTH 6090, Case Western Reserve University, 11100 Euclid Avenue, Cleveland, OH, USA
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Castro PA, Vago ER, Calvo EJ. Surface electrochemical transformations on spinel iron oxide electrodes in aqueous solutions. ACTA ACUST UNITED AC 1996. [DOI: 10.1039/ft9969203371] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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