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Aortic Depressor Nerve Morphology in Developing Spontaneously Hypertenvie Rats
Author(s) -
Amorim Milena Menezes,
Castania Jaci A,
Salgado Helio Cesar,
Fazan Valeria Paula Sassoli
Publication year - 2016
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.30.1_supplement.227.2
Subject(s) - anatomy , microneurography , medicine , axon , nodose ganglion , blood pressure , baroreflex , vagus nerve , heart rate , stimulation
Aortic Depressor Nerve (ADN) is an aferent nerve that originates on the aortic arch. Its major function is providing constant information about the body hemodynamics (beat by beat) to the Central Nervous System (NCS) in order to maintain cardiovascular homeostasis. This nerve is constituted by myelinated fibers (A‐type) and unmyelinated fibers (C‐type). In this study, we analyzed the myelinated fiber's morphology and morphometry in Spotaneously hypertensive rats (SHR) in different ages. We used SHR at 5 weeks (8 female, 5 male), 20 weeks (5 female, 8 male), 50 weeks (8 female, 9 male) of age and normotensive controls Wistar Kyoto rats (WKY) 20 weeks‐old (7 female, 6 male). All animals had their left ADN recorded for spontaneous activity associated with the arterial pressure pulse. After the electroneurographic recordings, proximal (close to nodose ganglion) and distal (at clavicle level) segments were prepared for epoxy resin embedding. Semithin cross sections of ADN segments were stained with 1% toluidine blue and analyzed by light microscopy. The morphometric study of the myelinated fibers was performed with the aid of computer software and took into consideration the myelinated fiber and respective axons area, diameter and the G ratio (axon diameter/fiber diameter). Comparison between proximal and distal segments made for the same strain, gender and age showed no morphometric differences. At 20 weeks of age, male WKY presented significantly larger number of fibers than male SHR, while comparisons between females showed no significant differences. The aging SHR morphometric data indicated that the nerve growth stopped at 20 weeks of age in both genders, suggesting that the 5 week old animals myelinated fibers are not fully developed for the best conduction velocity. Also, in elderly male SHR, the reduction of G ratio points to an axonal atrophy, that could explain, at least in part, the fact that males have higher blood pressure than females. Support or Funding Information FAPESP, CNPq, CAPES and FAEPA