Degeneration of vagal efferent axons and terminals in cardiac ganglia of aged rats

    Authors

    J. Ai; D. Gozal; L. H. Li; W. B. Wead; M. W. Chapleau; R. Wurster; B. F. Yang; H. L. Li; R. G. Liu;Z. X. Cheng

    Comments

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    Abbreviated Journal Title

    J. Comp. Neurol.

    Keywords

    baroreflex; anterograde tracing; brainstem; vagal; heart; aging; DIABETIC AUTONOMIC NEUROPATHY; DORSAL MOTOR NUCLEUS; HEART-RATE-VARIABILITY; PARASYMPATHETIC CONTROL; MYENTERIC PLEXUS; BAROREFLEX SENSITIVITY; PREGANGLIONIC NEURONS; FISCHER-344 RAT; NEURAL-CONTROL; MITRAL-VALVE; Neurosciences; Zoology

    Abstract

    Baroreflex control of the heart rate is significantly reduced during aging. However, neural mechanisms that underlie such a functional reduction are not fully understood. We injected the tracer Dil into the left nucleus ambiguus (NA), then used confocal microscopy and a Neurolucida Digitization System to examine qualitatively and quantitatively vagal efferent projections to cardiac ganglia of young adult (5-6 months) and aged (24-25 months) rats (Sprague Dawley). Fluoro-Gold was injected intraperitoneally to counterstain cardiac ganglionic principal neurons (PNs). In aged, as in young rats, NA axons projected to all cardiac ganglia and formed numerous basket endings around PNs in the hearts. However, significant structural changes were found in aged rats compared with young rats. Vagal efferent axons contained abnormally swollen axonal segments and exhibited reduced or even absent synaptic-like terminals around PNs, such that the numbers of vagal fibers and basket endings around PNs were substantially reduced (P < 0.01). Furthermore, synaptic-like varicose contacts of vagal cardiac axons with PNs were significantly reduced by approximately 50% (P < 0.01). These findings suggest that vagal efferents continue to maintain homeostatic control over the heart during aging. However, the marked morphological reorganization of vagal efferent axons and terminals in cardiac ganglia may represent the structural substrate for reduced vagal control of the heart rate and attenuated baroreflex function during aging. (c) 2007 Wiley-Liss, Inc.

    Journal Title

    Journal of Comparative Neurology

    Volume

    504

    Issue/Number

    1

    Publication Date

    1-1-2007

    Document Type

    Article

    Language

    English

    First Page

    74

    Last Page

    88

    WOS Identifier

    WOS:000248419000005

    ISSN

    0021-9967

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