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Chen J, Bendowski KT, Bizanti A, Zhang Y, Ma J, Hoover DB, Gozal D, Shivkumar K, Cheng ZJ. Distribution and morphology of calcitonin gene-related peptide (CGRP) innervation in flat mounts of whole rat atria and ventricles. Auton Neurosci 2024; 251:103127. [PMID: 38211380 DOI: 10.1016/j.autneu.2023.103127] [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: 09/18/2023] [Revised: 10/10/2023] [Accepted: 10/19/2023] [Indexed: 01/13/2024]
Abstract
Calcitonin gene-related peptide (CGRP) is widely used as a marker for nociceptive afferent axons. However, the distribution of CGRP-IR axons has not been fully determined in the whole rat heart. Immunohistochemically labeled flat-mounts of the right and left atria and ventricles, and the interventricular septum (IVS) in rats for CGRP were assessed with a Zeiss imager to generate complete montages of the entire atria, ventricles, and septum, and a confocal microscope was used to acquire detailed images of selected regions. We found that 1) CGRP-IR axons extensively innervated all regions of the atrial walls including the sinoatrial node region, auricles, atrioventricular node region, superior/inferior vena cava, left pre-caval vein, and pulmonary veins. 2) CGRP-IR axons formed varicose terminals around individual neurons in some cardiac ganglia but passed through other ganglia without making appositions with cardiac neurons. 3) Varicose CGRP-IR axons innervated the walls of blood vessels. 4) CGRP-IR axons extensively innervated the right/left ventricular walls and IVS. Our data shows the rather ubiquitous distribution of CGRP-IR axons in the whole rat heart at single-cell/axon/varicosity resolution for the first time. This study lays the foundation for future studies to quantify the differences in CGRP-IR axon innervation between sexes, disease models, and species.
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Affiliation(s)
- Jin Chen
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA.
| | - Kohlton T Bendowski
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA.
| | - Ariege Bizanti
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA
| | - Yuanyuan Zhang
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA
| | - Jichao Ma
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA
| | - Donald B Hoover
- Department of Biomedical Sciences, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, USA
| | - David Gozal
- Office of the Dean, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25701, USA
| | - Kalyanam Shivkumar
- Department of Medicine, Cardiac Arrhythmia Center and Neurocardiology Research Program of Excellence, University of California, Los Angeles, CA 90095, USA
| | - Zixi Jack Cheng
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL 32816, USA.
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Bizanti A, Zhang Y, Toledo Z, Bendowski KT, Harden SW, Mistareehi A, Chen J, Gozal D, Heal M, Christie R, Hunter PJ, Paton JFR, Cheng ZJ. Chronic intermittent hypoxia remodels catecholaminergic nerve innervation in mouse atria. J Physiol 2024; 602:49-71. [PMID: 38156943 PMCID: PMC10842556 DOI: 10.1113/jp284961] [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: 05/18/2023] [Accepted: 10/04/2023] [Indexed: 01/03/2024] Open
Abstract
Chronic intermittent hypoxia (CIH, a model for sleep apnoea) is a major risk factor for several cardiovascular diseases. Autonomic imbalance (sympathetic overactivity and parasympathetic withdrawal) has emerged as a causal contributor of CIH-induced cardiovascular disease. Previously, we showed that CIH remodels the parasympathetic pathway. However, whether CIH induces remodelling of the cardiac sympathetic innervation remains unknown. Mice (male, C57BL/6J, 2-3 months) were exposed to either room air (RA, 21% O2 ) or CIH (alternating 21% and 5.7% O2 , every 6 min, 10 h day-1 ) for 8-10 weeks. Flat-mounts of their left and right atria were immunohistochemically labelled for tyrosine hydroxylase (TH, a sympathetic marker). Using a confocal microscope (or fluorescence microscope) and Neurlocudia 360 digitization and tracing system, we scanned both the left and right atria and quantitatively analysed the sympathetic axon density in both groups. The segmentation data was mapped onto a 3D mouse heart scaffold. Our findings indicated that CIH significantly remodelled the TH immunoreactive (-IR) innervation of the atria by increasing its density at the sinoatrial node, the auricles and the major veins attached to the atria (P < 0.05, n = 7). Additionally, CIH increased the branching points of TH-IR axons and decreased the distance between varicosities. Abnormal patterns of TH-IR axons around intrinsic cardiac ganglia were also found following CIH. We postulate that the increased sympathetic innervation may further amplify the effects of enhanced CIH-induced central sympathetic drive to the heart. Our work provides an anatomical foundation for the understanding of CIH-induced autonomic imbalance. KEY POINTS: Chronic intermittent hypoxia (CIH, a model for sleep apnoea) causes sympathetic overactivity, cardiovascular remodelling and hypertension. We determined the effect of CIH on sympathetic innervation of the mouse atria. In vivo CIH for 8-10 weeks resulted in an aberrant axonal pattern around the principal neurons within intrinsic cardiac ganglia and an increase in the density, branching point, tortuosity of catecholaminergic axons and atrial wall thickness. Utilizing mapping tool available from NIH (SPARC) Program, the topographical distribution of the catecholaminergic innervation of the atria were integrated into a novel 3D heart scaffold for precise anatomical distribution and holistic quantitative comparison between normal and CIH mice. This work provides a unique neuroanatomical understanding of the pathophysiology of CIH-induced autonomic remodelling.
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Affiliation(s)
- Ariege Bizanti
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
| | - Yuanyuan Zhang
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
| | - Zulema Toledo
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
| | - Kohlton T Bendowski
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
| | - Scott W Harden
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
| | - Anas Mistareehi
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
| | - Jin Chen
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
| | - David Gozal
- Joan C. Edwards School of medicine, Marshall University, Huntington, WV, USA
| | - Maci Heal
- MBF Bioscience, Williston, Vermont, USA
| | - Richard Christie
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Peter J Hunter
- Auckland Bioengineering Institute, University of Auckland, Auckland, New Zealand
| | - Julian F R Paton
- Department Physiology, Manaaki Manawa-the Centre for Heart Research, University of Auckland, Auckland, New Zealand
| | - Zixi Jack Cheng
- Burnett School of Biomedical Sciences, College of Medicine, University of Central Florida, Orlando, FL, USA
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