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MORPHOLOGICAL REMODELING OF NUCLEUS AMBIGUUS (NA) PROJECTIONS TO CARDIAC GANGLIA IN F344 RATS FOLLOWING CHRONIC INTERMITTENT HYPOXIA (CIH)
Author(s) -
Ai Jing,
Yang Baofeng,
Cheng Zixi
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.a824
Subject(s) - nucleus ambiguus , hypoxia (environmental) , nucleus , cardiology , medicine , chemistry , neuroscience , biology , central nervous system , medulla oblongata , oxygen , organic chemistry
The baroreflex sensitivity is reduced following CIH. But the heart rate responses to electrical stimulation of the cervical vagus are significantly increased at low frequencies (Gu et al. 2007; EB Abstract). To elucidate the neural mechanisms for such paradoxical findings, F344 rats (3 months) were exposed to either room air (RA) or CIH for 35 days (n=6 /group). Confocal microscopy was used to examine vagal efferent axons and terminals in cardiac ganglia following FG injection to label cardiac ganglia and DiI microinjection into the left NA to label vagal efferents. We found that: Three cardiac ganglionic plexuses were distributed on the dorsal surface of atria. The size of the somata area of cardiac principal neurons (PNs) were significantly decreased following CIH (p <0.01). NA axons entered cardiac ganglia and innervated PNs with dense basket endings, and the density, i.e., the ratio of innervated and non‐innervated PNs by DiI labeled axons in ganglia, was similar (RA: 53.6±1.1% vs. CIH 54.5±0.6%). In CIH rats, however, swollen cardiac axons and degenerating terminals were found. Varicose endings around PNs appeared swollen and the number of axonal varicosities around PNs was significantly larger (RA: 148.6±0.9/PN vs. CIH: 174.6±1.1/PN, n=100 PNs, P<0.05). Thus, CIH significantly altered the structure of cardiac ganglia and reorganized vagal efferent projections to cardiac ganglia. This may provide new insights into the increased HR responses to vagal stimulation and parallel reductions in baroreflex sensitivity following CIH. Supported by NIH AG‐021020, HL‐79636, S10RR019391.