The distribution of nociceptive axons has not been fully determined in the whole rat and mouse heart. Previous anatomical studies have relied on sectioned tissue, which disrupts the organization of nerves and makes it more difficult to study their pattern, and most studies only used male tissues. We addressed this in the following two studies. First, flat-mounts of the right and left atria and ventricles, and the interventricular septum in rats were immunohistochemically labeled for calcitonin gene-related peptide (CGRP). Tissues were imaged with a high-quality microscope to generate complete montages and detailed images. We found that 1) CGRP-IR axons extensively innervated all regions of the atrial walls and the walls of the great vessels including the sinoatrial (SA) node region, auricles, atrioventricular (AV) 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. 3) Varicose CGRP-IR axons innervated the blood vessels. 4) CGRP-IR axons extensively innervated the right/left ventricular walls and interventricular septum. Second, flat-mount preparations of the left and right atria of male and female mice were labeled for CGRP, imaged, and digitally traced. The results show that 1) Large nerve bundle entry points and regional concentration of CGRP-IR axons were similar in both sexes. 2) The detailed distribution of nerves was digitized and mapped using sophisticated software and was similar between sexes. 3) Nerve density in the SA/AV node regions was not significantly different. 4) Morphometric parameters of varicosities in the auricle, SA/AV node regions was not significantly different between sexes. The distribution of CGRP-IR axons in the whole rat heart and the male/female mouse atria was shown for the first time at the single-cell/axon/varicosity resolution. Future studies will quantify the differences in CGRP-IR axon innervation between disease models, and other species.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:etd2023-1340 |
| Date | 01 January 2024 |
| Creators | Bendowski, Kohlton T |
| Publisher | STARS |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Graduate Thesis and Dissertation 2023-2024 |
| Rights | In copyright |
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