Lateral and longitudinal ultrastructural study of the recurrent laryngeal nerve in adult rats

Abstract

Despite the importance of the recurrent laryngeal nerve (RLN) in terms of respiration and phonation functions, studies on the normal histology of this nerve in rats are still scanty. The RLN is asymmetric in length, because the different origin on both sides but neither a longitudinal ultrastrucutral study nor information about ultrastructural lateral asymmetry of this nerve is available in rats. Male adult Wistar rats (N=5), had their RLN prepared for transmission electron microscopy and morphometry. Comparisons were made between segments on the same side and same levels between sides. The RLN fascicles are significantly larger proximally, on both sides as is the myelinated fiber number. No other longitudinal differences were observed. Unmyelinated fiber number and density is larger on right, compared to proximal left segment. This lateral difference was not present on the distal segments. No other lateral differences were observed. Our results indicate that the RLN are asymmetric not only macroscopically (origin and length, between sides) but also on its microscopic anatomy, not only between sides but also between proximal and distal segments. This information is crucial for those studies investigating RLN neuropathies since results can vary according to the nerve site studied.Grant Funding Source: FAPESP, CNPq, CAPES and FAEPA