Title

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

Authors

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

Authors: contact us about adding a copy of your work at STARS@ucf.edu

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

Share

COinS