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Tompkins JD, Hoover DB, Havton LA, Patel JC, Cho Y, Smith EH, Biscola NP, Ajijola OA, Shivkumar K, Ardell JL. Comparative specialization of intrinsic cardiac neurons in humans, mice, and pigs. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.04.588174. [PMID: 38645175 PMCID: PMC11030249 DOI: 10.1101/2024.04.04.588174] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Intrinsic cardiac neurons (ICNs) play a crucial role in the proper functioning of the heart; yet a paucity of data pertaining to human ICNs exists. We took a multidisciplinary approach to complete a detailed cellular comparison of the structure and function of ICNs from mice, pigs, and humans. Immunohistochemistry of whole and sectioned ganglia, transmission electron microscopy, intracellular microelectrode recording and dye filling for quantitative morphometry were used to define the neurophysiology, histochemistry, and ultrastructure of these cells across species. The densely packed, smaller ICNs of mouse lacked dendrites, formed axosomatic connections, and had high synaptic efficacy constituting an obligatory synapse. At Pig ICNs, a convergence of subthreshold cholinergic inputs onto extensive dendritic arbors supported greater summation and integration of synaptic input. Human ICNs were tonically firing, with synaptic stimulation evoking large suprathreshold excitatory postsynaptic potentials like mouse, and subthreshold potentials like pig. Ultrastructural examination of synaptic terminals revealed conserved architecture, yet small clear vesicles (SCVs) were larger in pigs and humans. The presence and localization of ganglionic neuropeptides was distinct, with abundant VIP observed in human but not pig or mouse ganglia, and little SP or CGRP in pig ganglia. Action potential waveforms were similar, but human ICNs had larger after-hyperpolarizations. Intrinsic excitability differed; 93% of human cells were tonic, all pig neurons were phasic, and both phasic and tonic phenotypes were observed in mouse. In combination, this publicly accessible, multimodal atlas of ICNs from mice, pigs, and humans identifies similarities and differences in the evolution of ICNs.
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Affiliation(s)
- John D. Tompkins
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Donald B. Hoover
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN, USA
| | - Leif A. Havton
- Departments of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, USA
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Janaki C. Patel
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Youngjin Cho
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Elizabeth H. Smith
- Department of Biomedical Sciences, Quillen College of Medicine, East Tennessee State University, Johnson City, TN, USA
| | - Natalia P. Biscola
- Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, USA
| | - Olujimi A. Ajijola
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Kalyanam Shivkumar
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Jeffrey L. Ardell
- UCLA Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
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Gurel NZ, Sudarshan KB, Tam S, Ly D, Armour JA, Kember G, Ajijola OA. Studying Cardiac Neural Network Dynamics: Challenges and Opportunities for Scientific Computing. Front Physiol 2022; 13:835761. [PMID: 35574437 PMCID: PMC9099376 DOI: 10.3389/fphys.2022.835761] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 04/06/2022] [Indexed: 11/13/2022] Open
Abstract
Neural control of the heart involves continuous modulation of cardiac mechanical and electrical activity to meet the organism's demand for blood flow. The closed-loop control scheme consists of interconnected neural networks with central and peripheral components working cooperatively with each other. These components have evolved to cooperate control of various aspects of cardiac function, which produce measurable "functional" outputs such as heart rate and blood pressure. In this review, we will outline fundamental studies probing the cardiac neural control hierarchy. We will discuss how computational methods can guide improved experimental design and be used to probe how information is processed while closed-loop control is operational. These experimental designs generate large cardio-neural datasets that require sophisticated strategies for signal processing and time series analysis, while presenting the usual large-scale computational challenges surrounding data sharing and reproducibility. These challenges provide unique opportunities for the development and validation of novel techniques to enhance understanding of mechanisms of cardiac pathologies required for clinical implementation.
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Affiliation(s)
- Nil Z. Gurel
- UCLA Neurocardiology Research Program of Excellence, Los Angeles, CA, United States
- UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, CA, United States
| | - Koustubh B. Sudarshan
- Department of Engineering Mathematics and Internetworking, Dalhousie University, Halifax, NS, Canada
| | - Sharon Tam
- UCLA Department of Bioengineering, Los Angeles, CA, United States
| | - Diana Ly
- UCLA Department of Bioengineering, Los Angeles, CA, United States
| | - J. Andrew Armour
- UCLA Neurocardiology Research Program of Excellence, Los Angeles, CA, United States
- UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, CA, United States
| | - Guy Kember
- Department of Engineering Mathematics and Internetworking, Dalhousie University, Halifax, NS, Canada
| | - Olujimi A. Ajijola
- UCLA Neurocardiology Research Program of Excellence, Los Angeles, CA, United States
- UCLA Cardiac Arrhythmia Center, UCLA Health System, Los Angeles, CA, United States
- Molecular, Cellular and Integrative Physiology Program, UCLA, Los Angeles, CA, United States
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Stoyek MR, Hortells L, Quinn TA. From Mice to Mainframes: Experimental Models for Investigation of the Intracardiac Nervous System. J Cardiovasc Dev Dis 2021; 8:149. [PMID: 34821702 PMCID: PMC8620975 DOI: 10.3390/jcdd8110149] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 10/28/2021] [Accepted: 11/01/2021] [Indexed: 01/17/2023] Open
Abstract
The intracardiac nervous system (IcNS), sometimes referred to as the "little brain" of the heart, is involved in modulating many aspects of cardiac physiology. In recent years our fundamental understanding of autonomic control of the heart has drastically improved, and the IcNS is increasingly being viewed as a therapeutic target in cardiovascular disease. However, investigations of the physiology and specific roles of intracardiac neurons within the neural circuitry mediating cardiac control has been hampered by an incomplete knowledge of the anatomical organisation of the IcNS. A more thorough understanding of the IcNS is hoped to promote the development of new, highly targeted therapies to modulate IcNS activity in cardiovascular disease. In this paper, we first provide an overview of IcNS anatomy and function derived from experiments in mammals. We then provide descriptions of alternate experimental models for investigation of the IcNS, focusing on a non-mammalian model (zebrafish), neuron-cardiomyocyte co-cultures, and computational models to demonstrate how the similarity of the relevant processes in each model can help to further our understanding of the IcNS in health and disease.
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Affiliation(s)
- Matthew R. Stoyek
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS 15000, Canada;
| | - Luis Hortells
- Institute for Experimental Cardiovascular Medicine, University Heart Centre Freiburg–Bad Krozingen, 79110 Freiburg, Germany;
- Faculty of Medicine, University of Freiburg, 79110 Freiburg, Germany
| | - T. Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, NS 15000, Canada;
- School of Biomedical Engineering, Dalhousie University, Halifax, NS 15000, Canada
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Fedele L, Brand T. The Intrinsic Cardiac Nervous System and Its Role in Cardiac Pacemaking and Conduction. J Cardiovasc Dev Dis 2020; 7:jcdd7040054. [PMID: 33255284 PMCID: PMC7712215 DOI: 10.3390/jcdd7040054] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2020] [Revised: 11/19/2020] [Accepted: 11/20/2020] [Indexed: 12/11/2022] Open
Abstract
The cardiac autonomic nervous system (CANS) plays a key role for the regulation of cardiac activity with its dysregulation being involved in various heart diseases, such as cardiac arrhythmias. The CANS comprises the extrinsic and intrinsic innervation of the heart. The intrinsic cardiac nervous system (ICNS) includes the network of the intracardiac ganglia and interconnecting neurons. The cardiac ganglia contribute to the tight modulation of cardiac electrophysiology, working as a local hub integrating the inputs of the extrinsic innervation and the ICNS. A better understanding of the role of the ICNS for the modulation of the cardiac conduction system will be crucial for targeted therapies of various arrhythmias. We describe the embryonic development, anatomy, and physiology of the ICNS. By correlating the topography of the intracardiac neurons with what is known regarding their biophysical and neurochemical properties, we outline their physiological role in the control of pacemaker activity of the sinoatrial and atrioventricular nodes. We conclude by highlighting cardiac disorders with a putative involvement of the ICNS and outline open questions that need to be addressed in order to better understand the physiology and pathophysiology of the ICNS.
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Affiliation(s)
- Laura Fedele
- Correspondence: (L.F.); (T.B.); Tel.: +44-(0)-207-594-6531 (L.F.); +44-(0)-207-594-8744 (T.B.)
| | - Thomas Brand
- Correspondence: (L.F.); (T.B.); Tel.: +44-(0)-207-594-6531 (L.F.); +44-(0)-207-594-8744 (T.B.)
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MacDonald EA, Stoyek MR, Rose RA, Quinn TA. Intrinsic regulation of sinoatrial node function and the zebrafish as a model of stretch effects on pacemaking. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2017; 130:198-211. [PMID: 28743586 DOI: 10.1016/j.pbiomolbio.2017.07.012] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2017] [Revised: 07/17/2017] [Accepted: 07/21/2017] [Indexed: 12/18/2022]
Abstract
Excitation of the heart occurs in a specialised region known as the sinoatrial node (SAN). Tight regulation of SAN function is essential for the maintenance of normal heart rhythm and the response to (patho-)physiological changes. The SAN is regulated by extrinsic (central nervous system) and intrinsic (neurons, peptides, mechanics) factors. The positive chronotropic response to stretch in particular is essential for beat-by-beat adaptation to changes in hemodynamic load. Yet, the mechanism of this stretch response is unknown, due in part to the lack of an appropriate experimental model for targeted investigations. We have been investigating the zebrafish as a model for the study of intrinsic regulation of SAN function. In this paper, we first briefly review current knowledge of the principal components of extrinsic and intrinsic SAN regulation, derived primarily from experiments in mammals, followed by a description of the zebrafish as a novel experimental model for studies of intrinsic SAN regulation. This mini-review is followed by an original investigation of the response of the zebrafish isolated SAN to controlled stretch. Stretch causes an immediate and continuous increase in beating rate in the zebrafish isolated SAN. This increase reaches a maximum part way through a period of sustained stretch, with the total change dependent on the magnitude and direction of stretch. This is comparable to what occurs in isolated SAN from most mammals (including human), suggesting that the zebrafish is a novel experimental model for the study of mechanisms involved in the intrinsic regulation of SAN function by mechanical effects.
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Affiliation(s)
- Eilidh A MacDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Canada
| | - Matthew R Stoyek
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Canada
| | - Robert A Rose
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - T Alexander Quinn
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Canada; School of Biomedical Engineering, Dalhousie University, Halifax, Canada.
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Smith FM, Vermeulen M, Cardinal R. Long-term spinal cord stimulation modifies canine intrinsic cardiac neuronal properties and ganglionic transmission during high-frequency repetitive activation. Physiol Rep 2016; 4:4/13/e12855. [PMID: 27401459 PMCID: PMC4945838 DOI: 10.14814/phy2.12855] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 06/16/2016] [Indexed: 12/28/2022] Open
Abstract
Long‐term spinal cord stimulation (SCS) applied to cranial thoracic SC segments exerts antiarrhythmic and cardioprotective actions in the canine heart in situ. We hypothesized that remodeling of intrinsic cardiac neuronal and synaptic properties occur in canines subjected to long‐term SCS, specifically that synaptic efficacy may be preferentially facilitated at high presynaptic nerve stimulation frequencies. Animals subjected to continuous SCS for 5–8 weeks (long‐term SCS: n = 17) or for 1 h (acute SCS: n = 4) were compared with corresponding control animals (long‐term: n = 15, acute: n = 4). At termination, animals were anesthetized, the heart was excised and neurones from the right atrial ganglionated plexus were identified and studied in vitro using standard intracellular microelectrode technique. Main findings were as follows: (1) a significant reduction in whole cell membrane input resistance and acceleration of the course of AHP decay identified among phasic neurones from long‐term SCS compared with controls, (2) significantly more robust synaptic transmission to rundown in long‐term SCS during high‐frequency (10–40 Hz) presynaptic nerve stimulation while recording from either phasic or accommodating postsynaptic neurones; this was associated with significantly greater posttrain excitatory postsynaptic potential (EPSP) numbers in long‐term SCS than control, and (3) synaptic efficacy was significantly decreased by atropine in both groups. Such changes did not occur in acute SCS. In conclusion, modification of intrinsic cardiac neuronal properties and facilitation of synaptic transmission at high stimulation frequency in long‐term SCS could improve physiologically modulated vagal inputs to the heart.
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Affiliation(s)
- Frank M Smith
- Department of Medical Neuroscience, Faculty of Medicine Dalhousie University, Halifax, Nova Scotia, Canada
| | - Michel Vermeulen
- Department of Pharmacology, Faculté de médecine Université de Montréal and Centre de recherche Hôpital du Sacré-Cœur de Montréal, Montréal, Quebec, Canada
| | - René Cardinal
- Department of Pharmacology, Faculté de médecine Université de Montréal and Centre de recherche Hôpital du Sacré-Cœur de Montréal, Montréal, Quebec, Canada
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Salavatian S, Beaumont E, Longpré JP, Armour JA, Vinet A, Jacquemet V, Shivkumar K, Ardell JL. Vagal stimulation targets select populations of intrinsic cardiac neurons to control neurally induced atrial fibrillation. Am J Physiol Heart Circ Physiol 2016; 311:H1311-H1320. [PMID: 27591222 DOI: 10.1152/ajpheart.00443.2016] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/20/2016] [Accepted: 08/30/2016] [Indexed: 12/30/2022]
Abstract
Mediastinal nerve stimulation (MNS) reproducibly evokes atrial fibrillation (AF) by excessive and heterogeneous activation of intrinsic cardiac (IC) neurons. This study evaluated whether preemptive vagus nerve stimulation (VNS) impacts MNS-induced evoked changes in IC neural network activity to thereby alter susceptibility to AF. IC neuronal activity in the right atrial ganglionated plexus was directly recorded in anesthetized canines (n = 8) using a linear microelectrode array concomitant with right atrial electrical activity in response to: 1) epicardial touch or great vessel occlusion vs. 2) stellate or vagal stimulation. From these stressors, post hoc analysis (based on the Skellam distribution) defined IC neurons so recorded as afferent, efferent, or convergent (afferent and efferent inputs) local circuit neurons (LCN). The capacity of right-sided MNS to modify IC activity in the induction of AF was determined before and after preemptive right (RCV)- vs. left (LCV)-sided VNS (15 Hz, 500 μs; 1.2× bradycardia threshold). Neuronal (n = 89) activity at baseline (0.11 ± 0.29 Hz) increased during MNS-induced AF (0.51 ± 1.30 Hz; P < 0.001). Convergent LCNs were preferentially activated by MNS. Preemptive RCV reduced MNS-induced changes in LCN activity (by 70%) while mitigating MNS-induced AF (by 75%). Preemptive LCV reduced LCN activity by 60% while mitigating AF potential by 40%. IC neuronal synchrony increased during neurally induced AF, a local neural network response mitigated by preemptive VNS. These antiarrhythmic effects persisted post-VNS for, on average, 26 min. In conclusion, VNS preferentially targets convergent LCNs and their interactive coherence to mitigate the potential for neurally induced AF. The antiarrhythmic properties imposed by VNS exhibit memory.
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Affiliation(s)
- Siamak Salavatian
- Faculty of Medicine, Department of Physiology, Université de Montréal, Quebec, Canada.,Centre de Recherche, Hôpital du Sacré-Coeur, Montréal, Quebec, Canada.,Neurocardiology Research Center of Excellence, University of California Los Angeles, Los Angeles, California; and
| | - Eric Beaumont
- Department of Biomedical Sciences, East Tennessee State University, Johnson City, Tennessee
| | - Jean-Philippe Longpré
- Faculty of Medicine, Department of Physiology, Université de Montréal, Quebec, Canada.,Centre de Recherche, Hôpital du Sacré-Coeur, Montréal, Quebec, Canada
| | - J Andrew Armour
- Neurocardiology Research Center of Excellence, University of California Los Angeles, Los Angeles, California; and.,Cardiac Arrhythmia Center, University of California Los Angeles, Los Angeles, California
| | - Alain Vinet
- Faculty of Medicine, Department of Physiology, Université de Montréal, Quebec, Canada.,Centre de Recherche, Hôpital du Sacré-Coeur, Montréal, Quebec, Canada
| | - Vincent Jacquemet
- Faculty of Medicine, Department of Physiology, Université de Montréal, Quebec, Canada.,Centre de Recherche, Hôpital du Sacré-Coeur, Montréal, Quebec, Canada
| | - Kalyanam Shivkumar
- Neurocardiology Research Center of Excellence, University of California Los Angeles, Los Angeles, California; and.,Cardiac Arrhythmia Center, University of California Los Angeles, Los Angeles, California
| | - Jeffrey L Ardell
- Neurocardiology Research Center of Excellence, University of California Los Angeles, Los Angeles, California; and .,Cardiac Arrhythmia Center, University of California Los Angeles, Los Angeles, California
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8
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Aging and magnetism: Presenting a possible new holistic paradigm for ameliorating the aging process and the effects thereof, through externally applied physiologic PicoTesla magnetic fields. Med Hypotheses 2015; 85:276-86. [PMID: 26092501 DOI: 10.1016/j.mehy.2015.05.018] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2015] [Revised: 05/03/2015] [Accepted: 05/27/2015] [Indexed: 11/20/2022]
Abstract
A new holistic paradigm is proposed for slowing our genomic-based biological clocks (e.g. regulation of telomere length), and decreasing heat energy exigencies for maintenance of physiologic homeostasis. Aging is considered the result of a progressive slow burn in small volumes of tissues with increase in the quantum entropic states; producing desiccation, microscopic scarring, and disruption of cooperative coherent states. Based upon piezoelectricity, i.e. photon-phonon transductions, physiologic PicoTesla range magnetic fields may decrease the production of excessive heat energy through target specific, bio molecular resonant interactions, renormalization of intrinsic electromagnetic tissue profiles, and autonomic modulation. Prospectively, we hypothesize that deleterious effects of physical trauma, immunogenic microbiological agents, stress, and anxiety may be ameliorated. A particle-wave equation is cited to ascertain magnetic field parameters for application to the whole organism thereby achieving desired homeostasis; secondary to restoration of structure and function on quantum levels. We hypothesize that it is at the atomic level that physical events shape the flow of signals and the transmission of energy in bio molecular systems. References are made to experimental data indicating the aspecific efficacy of non-ionizing physiologic magnetic field profiles for treatment of various pathologic states.
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Deng X, Guan C, Wang Y, Zhang B, Li S, Sun G, Hao L, Li G. Identification and detection of the isolated sinus venosus from the Asian toad. Cell Biochem Funct 2013; 31:660-7. [PMID: 23348247 DOI: 10.1002/cbf.2952] [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: 06/21/2012] [Revised: 11/05/2012] [Accepted: 12/11/2012] [Indexed: 11/09/2022]
Abstract
The pacemaker activity of mammalian sinoatrial node (SAN) of the heart plays a fundamental role in the integration of vital functions. Studying factors such as drugs that influence pacemaker activity of SAN has its significance. In this study, we isolated sinus venosus, SAN from toads (Bufo gargarizans), and analysed its electronic signal, histological characteristics and the influence of acetylcholine (ACh) and ivabradine on its pacemaker activity using PowerLab® and Chart® 5.0 software. We found that when isolated sinus venosus was treated with ACh, its histological distribution was disorganized and inter-beat (RR) interval was also broadened. The high frequency normalized unit (HFnu) and Poincaré plot of heart rate variability (HRV) of the isolated sinus venosus was also altered upon ACh treatment in a time-dependent and dose-dependent manner. When treated with ivabradine, these parameters of HRV such as square root of the mean of the squared differences between adjacent NN intervals (RMSSD) and HFnu were in the upward tendency, but low frequency normalized unit and low frequency/high frequency were in the opposite tendency. Taken together, we have developed a new model for studying the influences of drugs on autorhythmicity using isolated sinus venosus of the toad. With this model, we showed that ACh and ivabradine may affect the pacemaker activity by stimulating muscarinic receptor or inhibiting If current, respectively.
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Affiliation(s)
- Xin Deng
- The Experimental Center of Functional Subjects, College of Basic Medical Scientific Research, China Medical University, Shenyang, China
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Fischer H, Harper AA, Anderson CR, Adams DJ. Developmental changes in expression of GABAA receptor-channels in rat intrinsic cardiac ganglion neurones. J Physiol 2005; 564:465-74. [PMID: 15731187 PMCID: PMC1464452 DOI: 10.1113/jphysiol.2005.084012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
The effects of gamma-aminobutyric acid (GABA) on the electrophysiological properties of intracardiac neurones were investigated in the intracardiac ganglion plexus in situ and in dissociated neurones from neonatal, juvenile and adult rat hearts. Focal application of GABA evoked a depolarizing, excitatory response in both intact and dissociated intracardiac ganglion neurones. Under voltage clamp, both GABA and muscimol elicited inward currents at -60 mV in a concentration-dependent manner. The fast, desensitizing currents were mimicked by the GABA(A) receptor agonists muscimol and taurine, and inhibited by the GABA(A) receptor antagonists, bicuculline and picrotoxin. The GABA(A0) antagonist (1,2,5,6-tetrahydropyridin-4-yl)methyl phosphonic acid (TPMPA), had no effect on GABA-induced currents, suggesting that GABA(A) receptor-channels mediate the response. The GABA-evoked current amplitude recorded from dissociated neurones was age dependent whereby the peak current density measured at -100 mV was approximately 20 times higher for intracardiac neurones obtained from neonatal rats (P2-5) compared with adult rats (P45-49). The decrease in GABA sensitivity occurred during the first two postnatal weeks and coincides with maturation of the sympathetic innervation of the rat heart. Immunohistochemical staining using antibodies against GABA demonstrate the presence of GABA in the intracardiac ganglion plexus of the neonatal rat heart. Taken together, these results suggest that GABA and taurine may act as modulators of neurotransmission and cardiac function in the developing mammalian intrinsic cardiac nervous system.
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Affiliation(s)
- Harald Fischer
- School of Biomedical Sciences, University of Queensland, Brisbane QLD 4072, Australia
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Arora RC, Cardinal R, Smith FM, Ardell JL, Dell'Italia LJ, Armour JA. Intrinsic cardiac nervous system in tachycardia induced heart failure. Am J Physiol Regul Integr Comp Physiol 2003; 285:R1212-23. [PMID: 12893651 DOI: 10.1152/ajpregu.00131.2003] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The purpose of this study was to test the hypothesis that early-stage heart failure differentially affects the intrinsic cardiac nervous system's capacity to regulate cardiac function. After 2 wk of rapid ventricular pacing in nine anesthetized canines, cardiac and right atrial neuronal function were evaluated in situ in response to enhanced cardiac sensory inputs, stimulation of extracardiac autonomic efferent neuronal inputs, and close coronary arterial administration of neurochemicals that included nicotine. Right atrial neuronal intracellular electrophysiological properties were then evaluated in vitro in response to synaptic activation and nicotine. Intrinsic cardiac nicotine-sensitive, neuronally induced cardiac responses were also evaluated in eight sham-operated, unpaced animals. Two weeks of rapid ventricular pacing reduced the cardiac index by 54%. Intrinsic cardiac neurons of paced hearts maintained their cardiac mechano- and chemosensory transduction properties in vivo. They also responded normally to sympathetic and parasympathetic preganglionic efferent neuronal inputs, as well as to locally administered alpha-or beta-adrenergic agonists or angiotensin II. The dose of nicotine needed to modify intrinsic cardiac neurons was 50 times greater in failure compared with normal preparations. That dose failed to alter monitored cardiovascular indexes in failing preparations. Phasic and accommodating neurons identified in vitro displayed altered intracellular membrane properties compared with control, including decreased membrane resistance, indicative of reduced excitability. Early-stage heart failure differentially affects the intrinsic cardiac nervous system's capacity to regulate cardiodynamics. While maintaining its capacity to transduce cardiac mechano- and chemosensory inputs, as well as inputs from extracardiac autonomic efferent neurons, intrinsic cardiac nicotine-sensitive, local-circuit neurons differentially remodel such that their capacity to influence cardiodynamics becomes obtunded.
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Affiliation(s)
- Rakesh C Arora
- Centre de Recherche, Hôpital du Sacré-coeur, 5400 Boulevard Gouin ouest, Montréal, QC, Canada H4J 1C5
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Affiliation(s)
- Harald M Stauss
- Dept. of Exercise Science, The Univ. of Iowa, Iowa City, IA 52242, USA.
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De Biasi M. Nicotinic mechanisms in the autonomic control of organ systems. JOURNAL OF NEUROBIOLOGY 2002; 53:568-79. [PMID: 12436421 DOI: 10.1002/neu.10145] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Most visceral organs are under the control of the autonomic nervous system (ANS). Information on the state and function of these organs is constantly relayed to the central nervous system (CNS) by sensory afferent fibers. The CNS integrates the sensory inputs and sends neural commands back to the organ through the ANS. The autonomic ganglia are the final site for the integration of the message traveling from the CNS. Nicotinic acetylcholine receptors (nAChRs) are the main mediators of fast synaptic transmission in ganglia, and therefore, are key molecules for the processing of neural information in the ANS. This review focuses on the role of nAChRs in the control of organ systems such as heart, gut, and bladder. The autonomic control of these organ systems is discussed in the light of the results obtained from the analysis of mice carrying mutations targeted to nAChR subunits expressed in the ANS.
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Affiliation(s)
- Mariella De Biasi
- Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030, USA.
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