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Johnson SM, Gumnit MG, Johnson SM, Baker TL, Watters JJ. Disinhibition does not play a role in endomorphin-2-induced changes in inspiratory motoneuron output produced by in vitro neonatal rat preparations. Respir Physiol Neurobiol 2024; 320:104186. [PMID: 37944625 PMCID: PMC10843717 DOI: 10.1016/j.resp.2023.104186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2023] [Revised: 10/23/2023] [Accepted: 11/04/2023] [Indexed: 11/12/2023]
Abstract
Low level activation of mu-opioid receptors (MORs) in neonatal rat brainstem-spinal cord preparations increases inspiratory burst amplitude recorded on cervical spinal roots. We tested whether: (1) MOR activation with an endogenous ligand, such as endomorphin-2, increases inspiratory burst amplitude, (2) disinhibition of GABAergic or glycinergic inhibitory synaptic transmission is involved, and (3) inflammation alters endomorphin-2 effects. Using neonatal rat (P0-P3) brainstem-spinal cord preparations, bath-applied endomorphin-2 (10-200 nM) increased inspiratory burst amplitude and decreased burst frequency. Blockade of GABAA receptors (picrotoxin), glycine receptors (strychnine), or both (picrotoxin and strychnine) did not abolish endomorphin-2-induced effects. In preparations isolated from neonatal rats injected 3 h previously with lipopolysaccharide (LPS, 0.1 mg/kg), endomorphin-2 continued to decrease burst frequency but abolished the burst amplitude increase. Collectively, these data indicate that disinhibition of inhibitory synaptic transmission is unlikely to play a role in endomorphin-2-induced changes in inspiratory motor output, and that different mechanisms underlie the endomorphin-2-induced increases in inspiratory burst amplitude and decreases in burst frequency.
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Affiliation(s)
- Stephen M Johnson
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA.
| | - Maia G Gumnit
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Sarah M Johnson
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Tracy L Baker
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
| | - Jyoti J Watters
- Department of Comparative Biosciences, School of Veterinary Medicine, University of Wisconsin-Madison, Madison, WI, USA
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Pijnenburg R, Scholtens LH, Mantini D, Vanduffel W, Barrett LF, van den Heuvel MP. Biological Characteristics of Connection-Wise Resting-State Functional Connectivity Strength. Cereb Cortex 2019; 29:4646-4653. [PMID: 30668705 PMCID: PMC7049309 DOI: 10.1093/cercor/bhy342] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2018] [Revised: 12/18/2018] [Accepted: 12/19/2018] [Indexed: 01/21/2023] Open
Abstract
Functional connectivity is defined as the statistical dependency of neurophysiological activity between 2 separate brain areas. To investigate the biological characteristics of resting-state functional connectivity (rsFC)-and in particular the significance of connection-wise variation in time-series correlations-rsFC was compared with strychnine-based connectivity measured in the macaque. Strychnine neuronography is a historical technique that induces activity in cortical areas through means of local administration of the substance strychnine. Strychnine causes local disinhibition through GABA suppression and leads to subsequent activation of functional pathways. Multiple resting-state fMRI recordings were acquired in 4 macaques (examining in total 299 imaging runs) from which a group-averaged rsFC matrix was constructed. rsFC was observed to be higher (P < 0.0001) between region-pairs with a strychnine-based connection as compared with region-pairs with no strychnine-based connection present. In particular, higher resting-state connectivity was observed in connections that were relatively stronger (weak < moderate < strong; P < 0.01) and in connections that were bidirectional (P < 0.0001) instead of unidirectional in strychnine-based connectivity. Our results imply that the level of correlation between brain areas as extracted from resting-state fMRI relates to the strength of underlying interregional functional pathways.
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Affiliation(s)
- Rory Pijnenburg
- Connectome Lab, Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam Neuroscience, De Boelelaan 1081-1087, Amsterdam, The Netherlands
| | - Lianne H Scholtens
- Connectome Lab, Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam Neuroscience, De Boelelaan 1081-1087, Amsterdam, The Netherlands
| | - Dante Mantini
- Research Center for Motor Control and Neuroplasticity, KU Leuven, Tervuursevest 101 - Leuven, Belgium
- Functional Neuroimaging Laboratory, IRCCS San Camillo Hospital Foundation, Via Alberoni, 70, Lido VE, Italy
| | - Wim Vanduffel
- Laboratory for Neuro- and Psychophysiology, O&N II Herestraat 49 - Leuven, Belgium
- Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Radiology/NMR Ctr - 2nd FL 149 13th Street, Charlestown MA, USA
- Department of Psychiatry and Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, 149 Thirteenth Street, Suite 2301, Charlestown, MA, USA
| | - Lisa Feldman Barrett
- Department of Psychiatry and Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, 149 Thirteenth Street, Suite 2301, Charlestown, MA, USA
- Department of Psychology, Northeastern University, 125 NI (Nightingale Hall), Boston, MA, USA
| | - Martijn P van den Heuvel
- Connectome Lab, Department of Complex Trait Genetics, Center for Neurogenomics and Cognitive Research, Faculty of Science, Vrije Universiteit Amsterdam, Amsterdam Neuroscience, De Boelelaan 1081-1087, Amsterdam, The Netherlands
- Department of Clinical Genetics, VU University Medical Center, Amsterdam Neuroscience, De Boelelaan 1117, Amsterdam, The Netherlands
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Kilb W, Ikeda M, Uchida K, Okabe A, Fukuda A, Luhmann HJ. Depolarizing glycine responses in Cajal-Retzius cells of neonatal rat cerebral cortex. Neuroscience 2002; 112:299-307. [PMID: 12044448 DOI: 10.1016/s0306-4522(02)00071-4] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We investigated the properties of glycine-induced responses in Cajal-Retzius cells, a neuronal cell type essential for the establishment of neocortical lamination. Whole-cell and gramicidin-perforated patch-clamp recordings were performed on visually identified Cajal-Retzius cells in tangential slices from neonatal rat cortex (postnatal days 0-3). With a pipette Cl(-) concentration of 50 mM, bath application of 1 mM glycine induced a membrane depolarization of 32.8+/-7.4 mV and a massive decrease in membrane resistance by 88+/-1.4%. The membrane depolarization was abolished in the presence of the glycinergic antagonists strychnine (30 microM) and phenylbenzene-omega-phosphono-alpha-amino acid (100 microM), while the GABA(A) receptor antagonist bicuculline (100 microM) and the glutamatergic antagonist (+/-)-2-amino-5-phosphonopentatonic acid (60 microM) were without effect, suggesting that the glycine-induced membrane responses were mediated exclusively by the strychnine-sensitive glycine receptor. The EC(50) for activation of glycine receptors was 0.54 mM, 1.62 mM and 2.41 mM, for the glycinergic agonists glycine, beta-alanine and taurine, respectively. Since the reversal potential of the glycine-induced currents showed a strong dependency on the intracellular chloride concentration and was virtually unaffected under HCO(3)(-)-free conditions, the activation of glycine receptors was probably linked to Cl(-) fluxes with little contribution of HCO(3)(-) ions. Perforated patch recordings from Cajal-Retzius cells demonstrated that glycine elicited depolarizing responses mediated by Cl(-) currents which reversed at -41+/-3.7 mV. In summary, from these results we suggest that Cajal-Retzius cells of the neonatal rat cerebral cortex express functional strychnine-sensitive glycine receptors that mediate depolarizing membrane responses via Cl(-) efflux.
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Affiliation(s)
- W Kilb
- Institute of Neurophysiology, Heinrich-Heine-University Düsseldorf, P.O. Box 101007, D-40001 Düsseldorf, Germany.
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Stephan KE, Hilgetag CC, Burns GA, O'Neill MA, Young MP, Kötter R. Computational analysis of functional connectivity between areas of primate cerebral cortex. Philos Trans R Soc Lond B Biol Sci 2000; 355:111-26. [PMID: 10703047 PMCID: PMC1692715 DOI: 10.1098/rstb.2000.0552] [Citation(s) in RCA: 155] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recent analyses of association fibre networks in the primate cerebral cortex have revealed a small number of densely intra-connected and hierarchically organized structural systems. Corresponding analyses of data on functional connectivity are required to establish the significance of these structural systems. We therefore built up a relational database by systematically collating published data on the spread of activity after strychnine-induced disinhibition in the macaque cerebral cortex in vivo. After mapping these data to two different parcellation schemes, we used three independent methods of analysis which demonstrate that the cortical network of functional interactions is not homogeneous, but shows a clear segregation into functional assemblies of mutually interacting areas. The assemblies suggest a principal division of the cortex into visual, somatomotor and orbito-temporo-insular systems, while motor and somatosensory areas are inseparably interrelated. These results are largely compatible with corresponding analyses of structural data of mammalian cerebral cortex, and deliver the first functional evidence for 'small-world' architecture of primate cerebral cortex.
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Affiliation(s)
- K E Stephan
- C. & O. Vogt Brain Research Institute, Heinrich Heine University, Düsseldorf, Germany
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Kötter R, Sommer FT. Global relationship between anatomical connectivity and activity propagation in the cerebral cortex. Philos Trans R Soc Lond B Biol Sci 2000; 355:127-34. [PMID: 10703048 PMCID: PMC1692719 DOI: 10.1098/rstb.2000.0553] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Anatomical connectivity is a prerequisite for cooperative interactions between cortical areas, but it has yet to be demonstrated that association fibre networks determine the macroscopical flow of activity in the cerebral cortex. To test this notion, we constructed a large-scale model of cortical areas whose interconnections were based on published anatomical data from tracing studies. Using this model we simulated the propagation of activity in response to activation of individual cortical areas and compared the resulting topographic activation patterns to electrophysiological observations on the global spread of epileptic activity following intracortical stimulation. Here we show that a neural network with connectivity derived from experimental data reproduces cortical propagation of activity significantly better than networks with different types of neighbourhood-based connectivity or random connections. Our results indicate that association fibres and their relative connection strengths are useful predictors of global topographic activation patterns in the cerebral cortex. This global structure-function relationship may open a door to explicit interpretation of cortical activation data in terms of underlying anatomical connectivity.
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Affiliation(s)
- R Kötter
- C. & O. Vogt Brain Research Institute, Heinrich Heine University, Düsseldorf, Germany.
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Shao XM, Feldman JL. Respiratory rhythm generation and synaptic inhibition of expiratory neurons in pre-Bötzinger complex: differential roles of glycinergic and GABAergic neural transmission. J Neurophysiol 1997; 77:1853-60. [PMID: 9114241 DOI: 10.1152/jn.1997.77.4.1853] [Citation(s) in RCA: 180] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A key distinction between neural pacemaker and conventional network models for the generation of breathing rhythm in mammals is whether phasic reciprocal inhibitory interactions between inspiratory and expiratory neurons are required. In medullary slices from neonatal rats generating respiratory-related rhythm, we measured the phasic inhibitory inputs to expiratory neurons with the use of whole cell patch clamp in the hypothesized rhythm generation site, the pre-Bötzinger complex (pre-BötC). Expiratory neurons, which generate tonic impulse activity during the expiratory period, exhibited inhibitory postsynaptic potentials (IPSPs) synchronized to the periodic inspiratory bursts of the hypoglossal nerve root (XIIn). Bath application of the glycine receptor antagonist strychnine (STR; 5-10 microM) reversibly blocked these inspiratory-phase IPSPs, whereas the gamma-aminobutyric acid-A (GABA(A)) receptor antagonist bicuculline (BIC; 10-100 microM) had no effect on these IPSPs. Replacing the control in vitro bathing solution with a Cl(-)-free solution also abolished these IPSPs. Respiratory-related rhythmic activity was not abolished when inspiratory-phase IPSPs were blocked. The frequency and strength of XIIn rhythmic activity increased and seizurelike activity was produced when either STR, BIC, or Cl(-)-free solution was applied. Inspiratory-phase IPSPs were stable after establishment of whole cell patch conditions (patch pipettes contained 7 mM Cl-). Under voltage clamp, the reversal potential of inspiratory-phase inhibitory postsynaptic currents (IPSCs) was -75 mV. The current-voltage (I-V) curve for IPSCs shifted to the right when extracellular Cl- concentration was reduced by 50% (70 mM) and the reversal potential was reduced to -60 mV, close to the new Cl- Nernst potential. In tetrodotoxin (0.5 microM) under voltage clamp (holding potential = -45 mV), local application of glycine (1 mM) over pre-BötC induced an outward current and an increase in membrane conductance in expiratory neurons. The effect was blocked by bath application of STR (0.8-1 microM). Local application of the GABA(A) receptor agonist 4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol (THIP, 1 mM) induced an outward current and an increase in membrane conductance that was blocked by BIC (10-100 mM). Under voltage clamp (holding potential = -45 mV), we analyzed spontaneous IPSCs during expiration in expiratory neurons. Bath application of BIC (10 microM) reduced the IPSC frequency (from 2.2 to 0.3 per s), whereas the inspiratory-phase IPSCs did not change. Bath application of STR (8-10 microM) abolished both IPSCs. These results indicate that 1) reciprocal inhibition of expiratory neurons is glycinergic and mediated by a glycine-activated Cl- channel that is not required for respiratory-related rhythm generation in neonatal rat medullary slices; 2) endogenous GABA and glycine modulate the excitability of respiratory neurons and affect respiratory pattern in the slice preparation; 3) both glycine and GABA(A) receptors are found on pre-BötC expiratory neurons, and these receptors are sensitive to STR and BIC, respectively; 4) glycine and GABA(A) inhibitory mechanisms play different functional roles in expiratory neurons: both glycine and GABA(A) receptors modulate neuronal excitability, whereas glycinergic transmission alone is responsible for reciprocal inhibition; and 5) intracellular Cl- concentration in these neonatal expiratory neurons is similar to that in adults.
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Affiliation(s)
- X M Shao
- Department of Neurobiology, University of California, Los Angeles 90095-1527, USA
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