Presence and co-localization of vasoactive intestinal polypeptide with neuronal nitric oxide synthase in cells and nerve fibers within guinea pig intrinsic cardiac ganglia and cardiac tissue |
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Authors: | Rodney L Parsons Sarah A Locknar Beth A Young Jennifer L Hoard Donald B Hoover |
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Institution: | (1) Department of Anatomy and Neurobiology, College of Medicine, University of Vermont, Burlington, VT 05405, USA;(2) Department of Pharmacology, James H. Quillen College of Medicine, East Tennessee State University, Johnson City, TN 37614, USA |
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Abstract: | The presence of vasoactive intestinal polypeptide (VIP) has been analyzed in fibers and neurons within the guinea pig intrinsic
cardiac ganglia and in fibers innervating cardiac tissues. In whole-mount preparations, VIP-immunoreactive (IR) fibers were
present in about 70% of the cardiac ganglia. VIP was co-localized with neuronal nitric oxide synthase (nNOS) in fibers innervating
the intrinsic ganglia but was not present in fibers immunoreactive for pituitary adenylate cyclase-activating polypeptide,
choline acetyltransferase (ChAT), tyrosine hydroxylase, or substance P. A small number of the intrinsic ChAT-IR cardiac ganglia
neurons (approximately 3%) exhibited VIP immunoreactivity. These few VIP-IR cardiac neurons also exhibited nNOS immunoreactivity.
After explant culture for 72 h, the intraganglionic VIP-IR fibers degenerated, indicating that they were axons of neurons
located outside the heart. In cardiac tissue sections, VIP-IR fibers were present primarily in the atria and in perivascular
connective tissue, with the overall abundance being low. VIP-IR fibers were notably sparse in the sinus node and conducting
system and generally absent in the ventricular myocardium. Virtually all VIP-IR fibers in tissue sections exhibited immunoreactivity
to nNOS. A few VIP-IR fibers, primarily those located within the atrial myocardium, were immunoreactive for both nNOS and
ChAT indicating they were derived from intrinsic cardiac neurons. We suggest that, in the guinea pig, the majority of intraganglionic
and cardiac tissue VIP-IR fibers originate outside of the heart. These extrinsic VIP-IR fibers are also immunoreactive for
nNOS and therefore most likely are a component of the afferent fibers derived from the vagal sensory ganglia.
This work was supported by NIH grant HL65481 (R.L.P.) and HL54633 (D.B.H.). Use of the DeltaVision Restoration microscope
was provided through the Imaging/Physiology Core supported by NIH Grant P20 RR16435 from the COBRE program of the National
Center for Research Resources |
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Keywords: | Neuropeptide Autonomic neuron Intrinsic cardiac ganglia Vagal afferent fibers Guinea pig (Hartley) |
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