VAGAL AFFERENT INNERVATION AND REMODELING IN THE AORTIC ARCH OF YOUNG-ADULT FISCHER 344 RATS FOLLOWING CHRONIC INTERMITTENT HYPOXIA

    Authors

    J. Al; R. D. Wurster; S. W. Harden;Z. J. Cheng

    Comments

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    Abbreviated Journal Title

    Neuroscience

    Keywords

    baroreflex; nodose ganglia; baroreceptor afferent; aortic arch; chronic; intermittent hypoxia; sleep apnea; INJURY; HEART; MICE; BAROREFLEX; Neurosciences

    Abstract

    Previously, we have shown that chronic intermittent hypoxia (CIH) impairs baroreflex control of heart rate and augments aortic baroreceptor afferent function. In the present study, we examined whether CIH induces structural changes of aortic afferent axons and terminals. Young-adult Fischer 344 (17344, 4 months old) rats were exposed to room air (RA) or CIH for 35-45 days. After 14-24 days of exposure, they received tracer Dil injection into the left nodose ganglion to anterogradely label vagal afferent nerves. After surgery, animals were returned to their cages to continue RA or CIH exposure. Twenty-one days after Dil injection, the animals were sacrificed and the aortic arch was examined using confocal microscopy. In both RA and CIH rats, we found that Dil-labeled vagal afferent axons entered the wall of the aortic arch, then fanned out and branched into large receptive fields with numerous terminals (flower-sprays, end-nets and free endings). Vagal afferent axons projected much more to the anterior wall than to the posterior wall. In general, the flower-sprays, end-nets and free endings were widely and similarly distributed in the aortic arch of both groups. However, several salient differences between RA and CIH rats were found. Compared to RA control, CIH rats appeared to have larger vagal afferent receptive fields. The CIH rats had many abnormal flower-sprays, end-nets, and free endings which were intermingled and diffused into "bush-like" structures. However, the total number of flower-sprays was comparable (P>0.05). Since there was a large variance of the size of flower-sprays, we only sampled the 10 largest flower-sprays from each animal. CIH substantially increased the size of large flower-sprays (P < 0.01). Numerous free endings with enlarged varicosities were identified, resembling axonal sprouting structures. Taken together, our data indicate that CIH induces significant remodeling of afferent terminal structures in the aortic arch of F344 rats. We suggest that such an enlargement of vagal afferent terminals may contribute to altered aortic baroreceptor function following CIH. (C) 2009 IBRO. Published by Elsevier Ltd. All rights reserved.

    Journal Title

    Neuroscience

    Volume

    164

    Issue/Number

    2

    Publication Date

    1-1-2009

    Document Type

    Article

    Language

    English

    First Page

    658

    Last Page

    666

    WOS Identifier

    WOS:000271731700032

    ISSN

    0306-4522

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