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Zuperku EJ, Hopp FA, Stucke AG. Pulmonary stretch receptor modulation of synaptic inhibition shapes the discharge pattern of respiratory premotor neurons. Respir Physiol Neurobiol 2025; 336:104420. [PMID: 40147693 DOI: 10.1016/j.resp.2025.104420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2024] [Revised: 02/22/2025] [Accepted: 03/21/2025] [Indexed: 03/29/2025]
Abstract
Many studies focus on the mechanisms of respiratory rhythm generation through neuronal interactions in the preBötzinger and Bötzinger complex area. There is limited insight into how the varied discharge patterns of propriobulbar, rhythm generating neurons are integrated to generate the slowly augmenting and decrementing discharge patterns observed in respiratory premotor neurons. Neuronal discharge patterns were obtained, in vivo, from inspiratory (I) and expiratory (E) premotor neurons in the ventral respiratory group of adult, anesthetized and vagotomized canines. Electrical activation of vagal afferents was used to produce pulmonary stretch receptor (PSR), step-input patterns, throughout or within either the I- or E-phase. PSR inputs decreased the discharge pattern slopes of augmenting and decrementing E-neurons and increased the slopes of augmenting and decrementing I-neurons. PSR inputs that were applied only for part of the phase acutely changed the discharge pattern to the trajectory associated with those PSR throughout-phase inputs, but the pattern returned immediately to the original trajectory after the PSR input terminated. These types of responses can be reproduced with high fidelity by a mathematical model based on reciprocal inhibition between augmenting and decrementing neurons of the same respiratory phase. Best fit is achieved when PSR inputs solely modulate the strength of the synaptic inhibition of decrementing neurons by augmenting neurons at the presynaptic level. Leaky integrator functions are not necessary to generate the gradually augmenting and decrementing patterns. This model offers a novel and different mechanistic way to conceptualize the generation and PSR control of respiratory discharge patterns.
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Affiliation(s)
- Edward J Zuperku
- Zablocki Veterans Administration Medical Center, Milwaukee, WI, United States; Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - Francis A Hopp
- Zablocki Veterans Administration Medical Center, Milwaukee, WI, United States
| | - Astrid G Stucke
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee, WI, United States; Children's Wisconsin, Milwaukee, WI, United States.
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Weiss J, Zufall F. Presynaptic GABA B receptors inhibit vomeronasal nerve transmission to accessory olfactory bulb mitral cells. Front Cell Neurosci 2023; 17:1302955. [PMID: 38130867 PMCID: PMC10733964 DOI: 10.3389/fncel.2023.1302955] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2023] [Accepted: 11/08/2023] [Indexed: 12/23/2023] Open
Abstract
Vomeronasal sensory neurons (VSNs) recognize pheromonal and kairomonal semiochemicals in the lumen of the vomeronasal organ. VSNs send their axons along the vomeronasal nerve (VN) into multiple glomeruli of the accessory olfactory bulb (AOB) and form glutamatergic synapses with apical dendrites of mitral cells, the projection neurons of the AOB. Juxtaglomerular interneurons release the inhibitory neurotransmitter γ-aminobutyric acid (GABA). Besides ionotropic GABA receptors, the metabotropic GABAB receptor has been shown to modulate synaptic transmission in the main olfactory system. Here we show that GABAB receptors are expressed in the AOB and are primarily located at VN terminals. Electrical stimulation of the VN provokes calcium elevations in VSN nerve terminals, and activation of GABAB receptors by the agonist baclofen abolishes calcium influx in AOB slice preparations. Patch clamp recordings reveal that synaptic transmission from the VN to mitral cells can be completely suppressed by activation of GABAB receptors. A potent GABAB receptor antagonist, CGP 52432, reversed the baclofen-induced effects. These results indicate that modulation of VSNs via activation of GABAB receptors affects calcium influx and glutamate release at presynaptic terminals and likely balances synaptic transmission at the first synapse of the accessory olfactory system.
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Affiliation(s)
- Jan Weiss
- Center for Integrative Physiology and Molecular Medicine (CIPMM), Saarland University, Homburg, Germany
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Abstract
A substantial fraction of the human population suffers from chronic pain states, which often cannot be sufficiently treated with existing drugs. This calls for alternative targets and strategies for the development of novel analgesics. There is substantial evidence that the G protein-coupled GABAB receptor is involved in the processing of pain signals and thus has long been considered a valuable target for the generation of analgesics to treat chronic pain. In this review, the contribution of GABAB receptors to the generation and modulation of pain signals, their involvement in chronic pain states as well as their target suitability for the development of novel analgesics is discussed.
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Affiliation(s)
- Dietmar Benke
- Institute of Pharmacology and Toxicology, University of Zurich, Zurich, Switzerland.
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Crane JW, Holmes NM, Fam J, Westbrook RF, Delaney AJ. Oxytocin increases inhibitory synaptic transmission and blocks development of long-term potentiation in the lateral amygdala. J Neurophysiol 2020; 123:587-599. [DOI: 10.1152/jn.00571.2019] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Oxytocin (OT) is a neuroactive peptide that influences the processing of fearful stimuli in the amygdala. In the central nucleus of the amygdala, the activation of OT receptors alters neural activity and ultimately suppresses the behavioral response to a fear conditioned stimulus. Receptors for OT are also found in the lateral amygdala (LA), and infusion of OT into the basolateral amygdala complex affects the formation and consolidation of fear memories. Yet, how OT receptor activation alters neurons and neural networks in the LA is unknown. In this study we used whole cell electrophysiological recordings to determine how OT-receptor activation changes synaptic transmission and synaptic plasticity in the LA of Sprague-Dawley rats. Our results demonstrate that OT-receptor activation results in a 200% increase in spontaneous inhibitory transmission in the LA that leads to the activation of presynaptic GABAB receptors. The activation of these receptors inhibits excitatory transmission in the LA, blocking long-term potentiation of cortical inputs onto LA neurons. Hence, this study provides the first demonstration that OT influences synaptic transmission and plasticity in the LA, revealing a mechanism that could explain how OT regulates the formation and consolidation of conditioned fear memories in the amygdala. NEW & NOTEWORTHY This study investigates modulation of synaptic transmission by oxytocin (OT) in the lateral amygdala (LA). We demonstrate that OT induces transient increases in spontaneous GABAergic transmission by activating interneurons in the basolateral amygdala. The resultant increase in GABA release in the LA activates presynaptic GABAB receptors on both inhibitory and excitatory inputs onto LA neurons, reducing release probability at these synapses. We subsequently demonstrate that OT modulates synaptic plasticity at cortical inputs to the LA.
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Affiliation(s)
- J. W. Crane
- School of Biomedical Sciences, Charles Sturt University, Orange, New South Wales, Australia
- School of Medicine, University of Tasmania, Hobart, Tasmania, Australia
| | - N. M. Holmes
- School of Psychology, University of New South Wales, Sydney, New South Wales, Australia
| | - J. Fam
- School of Psychology, University of New South Wales, Sydney, New South Wales, Australia
| | - R. F. Westbrook
- School of Psychology, University of New South Wales, Sydney, New South Wales, Australia
| | - A. J. Delaney
- School of Biomedical Sciences, Charles Sturt University, Orange, New South Wales, Australia
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Delaney AJ, Crane JW, Holmes NM, Fam J, Westbrook RF. Baclofen acts in the central amygdala to reduce synaptic transmission and impair context fear conditioning. Sci Rep 2018; 8:9908. [PMID: 29967489 PMCID: PMC6028433 DOI: 10.1038/s41598-018-28321-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2018] [Accepted: 06/15/2018] [Indexed: 12/14/2022] Open
Abstract
The two main sub-divisions of the Central amygdala (CeA), the lateral-capsular (CeA-LC) and the medial (CeA-M), contain extensive networks of inhibitory interneurons. We have previously shown that activation of GABAB-receptors reduces excitatory transmission between axons of the pontine parabrachial nucleus and neurons of the CeA-LC by inhibiting glutamate release from presynaptic terminals13. Here we have characterised GABAB-receptor activation on other excitatory and inhibitory projections within the CeA. Using whole-cell, patch-clamp recordings, we found that the GABAB-receptor agonist baclofen significantly reduced excitatory and inhibitory transmission from all tested inputs into the CeA-LC and CeA-M. In all but one of the inputs, reductions in transmission were accompanied by an increase in paired pulse ratio, indicating that presynaptic GABAB-receptors acted to reduce the release probability of synaptic vesicles. To examine the impact of GABAB-receptors in the CeA on contextual fear-conditioning, we infused baclofen into the CeA immediately prior to training. Compared to vehicle-infused rats, baclofen-infused rats displayed significantly less freezing both during the final stages of the training period and at test 24 hours later. The results of this study demonstrate that, by suppressing excitatory and inhibitory transmission, activation of presynaptic GABAB-receptors in the CeA inhibits the development of context conditioned fear.
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Affiliation(s)
- A J Delaney
- School of Biomedical Sciences, Charles Sturt University, Orange, NSW, 2800, Australia.
| | - J W Crane
- School of Medicine, University of Tasmania, Hobart, TAS, 7000, Australia
| | - N M Holmes
- School of Psychology, University of New South Wales, Sydney, NSW, 2052, Australia
| | - J Fam
- School of Psychology, University of New South Wales, Sydney, NSW, 2052, Australia
| | - R F Westbrook
- School of Psychology, University of New South Wales, Sydney, NSW, 2052, Australia
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Wiegert JS, Mahn M, Prigge M, Printz Y, Yizhar O. Silencing Neurons: Tools, Applications, and Experimental Constraints. Neuron 2017; 95:504-529. [PMID: 28772120 DOI: 10.1016/j.neuron.2017.06.050] [Citation(s) in RCA: 197] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 06/29/2017] [Accepted: 06/30/2017] [Indexed: 12/16/2022]
Abstract
Reversible silencing of neuronal activity is a powerful approach for isolating the roles of specific neuronal populations in circuit dynamics and behavior. In contrast with neuronal excitation, for which the majority of studies have used a limited number of optogenetic and chemogenetic tools, the number of genetically encoded tools used for inhibition of neuronal activity has vastly expanded. Silencing strategies vary widely in their mechanism of action and in their spatial and temporal scales. Although such manipulations are commonly applied, the design and interpretation of neuronal silencing experiments present unique challenges, both technically and conceptually. Here, we review the most commonly used tools for silencing neuronal activity and provide an in-depth analysis of their mechanism of action and utility for particular experimental applications. We further discuss the considerations that need to be given to experimental design, analysis, and interpretation of collected data. Finally, we discuss future directions for the development of new silencing approaches in neuroscience.
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Affiliation(s)
- J Simon Wiegert
- Research Group Synaptic Wiring and Information Processing, Center for Molecular Neurobiology Hamburg, Falkenried 94, 20251 Hamburg, Germany
| | - Mathias Mahn
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Matthias Prigge
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Yoav Printz
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel
| | - Ofer Yizhar
- Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
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