Neurochemical diversity of afferent neurons that transduce sensory signals from dog ventricular myocardium.
While much is known about the influence of ventricular afferent neurons on cardiovascular function in the dog, identification of the neurochemicals transmitting cardiac afferent signals to central neurons is lacking. Accordingly, we identified ventricular afferent neurons in canine dorsal root ganglia (DRG) and nodose ganglia by retrograde labeling after injecting horseradish peroxidase (HRP) into the anterior right and left ventricles. Primary antibodies from three host species were used in immunohistochemical experiments to simultaneously evaluate afferent somata for the presence of HRP and markers for two neurotransmitters. Only a small percentage (2%) of afferent somata were labeled with HRP. About half of the HRP-identified ventricular afferent neurons in T(3) DRG also stained for substance P (SP), calcitonin gene-related peptide (CGRP), or neuronal nitric oxide synthase (nNOS), either alone or with two markers colocalized. Ventricular afferent neurons and the general population of T(3) DRG neurons showed the same labeling profiles; CGRP (alone or colocalized with SP) being the most common (30-40% of ventricular afferent somata in T(3) DRG). About 30% of the ventricular afferent neurons in T(2) DRG displayed CGRP immunoreactivity and binding of the putative nociceptive marker IB(4). Ventricular afferent neurons of the nodose ganglia were distinct from those in the DRG by having smaller size and lacking immunoreactivity for SP, CGRP, and nNOS. These findings suggest that ventricular sensory information is transferred to the central nervous system by relatively small populations of vagal and spinal afferent neurons and that spinal afferents use a variety of neurotransmitters.
Department of Pharmacology, College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States.
Donald B
DB
Hoover
Department of Pharmacology, College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States.
Angela V
AV
Shepherd
Department of Pharmacology, College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States.
E Marie
EM
Southerland
Faculty of Medicine, University of Montreal, Montreal, Quebec, Canada.
J Andrew
JA
Armour
Department of Pharmacology, College of Medicine, East Tennessee State University, Johnson City, TN 37614, United States. Electronic address: ardellj@etsu.edu.
Jeffrey L
JL
Ardell
D000344:Afferent Pathways / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000378:metabolism; D002452:Cell Count; D004285:Dogs; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology / Q000378:metabolism*; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D007150:Immunohistochemistry; D037102:Lectins / Q000378:metabolism; D008297:Male; D018613:Microscopy, Confocal; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009475:Neurons, Afferent / Q000166:cytology / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D009619:Nociceptors / Q000378:metabolism; D009620:Nodose Ganglion / Q000166:cytology / Q000378:metabolism; D015398:Signal Transduction; D013373:Substance P / Q000378:metabolism; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism; D050599:Vesicular Glutamate Transport Protein 2 / Q000378:metabolism
D037102:Lectins; D050598:Vesicular Glutamate Transport Protein 1; D050599:Vesicular Glutamate Transport Protein 2; D013373:Substance P; D052248:Nitric Oxide Synthase Type I; D015740:Calcitonin Gene-Related Peptide