Anterograde tracing of spinal afferent innervation in flat-mounts of the rat atria

Study Purpose: The spinal afferent innervation of the heart regulates cardiac function by sending sensory information through the dorsal root ganglia (DRG) to the brain. However, the distribution and morphology of spinal afferent axons in the heart have not been well characterized. In this study, we injected anterograde tracer Dextran Biotin (DB) into the left DRG C8-T3, cervical level 8 to thoracic 3, characterize spinal afferent axons and their terminal structures in flat-mounts of the whole rat atria.

Data Collection: This dataset displays the digitally traced spinal afferent axons and their terminal structures in flat-mounts of the whole Sprague-Dawley rat left and right atria using tracer Dextran Biotin into the left DRG C8-T3.

Primary Conclusion: Our results showed that DB-labeled axons entered the left precaval vein and projected to the left and right atria, with predominant projection in the left atrial wall. DB-labeled varicose axons were observed in different layers, mostly in the epicardium and myocardium, but much less in the endocardium. In those layers, these spinal afferent axons branched out into simple to complex terminal arborizations, forming close appositions with cardiac muscles, intrinsic cardiac ganglia, blood vessels, and fat tissue. This work, for the first time, characterized cardiac spinal afferent distribution of the rat atria using anterograde tracing, which will provide the foundation for future studies of topographical cardiac spinal afferent innervation and remodeling in heart disease models.

Curator's Notes

Experimental Design: A mixture of dextran-conjugates was injected into the dorsal root ganglia C8-T3 of adult Sprague-Dawley rats. 16 days after the tracer injection, the animals were sacrificed, and the left and right atria were prepared and processed for avidin-biotin permanent labeling and Cuprolinic Blue labeling. All flat-mounts were examined using a Zeiss M2 Imager and MicroBrightField’s Neurolucida tracing and digitization system to determine the distribution and terminal structures of spinal afferent axons.

Completeness: This dataset is part of a larger study: "Nociceptive Afferent Topographical Innervation of the Heart and Stomach"

Subjects & Samples: Male (n=13) adult Sprague Dawley (RRID: RGD_737903) rats were used in this study.

Primary vs. derivative data: Primary data is organized in folders by subject ID and subfolders denoted by sample ID. Each folder contains the data in .xml files, which are tracings of the spinal afferent axons in the flat-mount of the whole left and right atria. The data is also available in .TIF and .czi files, which are single optical sections of representative axons. Primary .czi data images are converted to (JPEG2000 and OME-TIFF) formats for web streaming and visualization on the SPARC Data Portal. These converted images are stored in the derivative data folder.