Phrenic nerve morphometry in male and female spontaneously hypertensive rats

Abstract

Histological examination of the diaphragm showed gender differences in fiber composition but gender differences on phrenic nerve morphometry were not thoroughly addressed. Ventilatory differences were described between male and female rats, as well as among different rat strains. However, the morphology of the phrenic nerve was not investigated in spontaneously hypertensive (SHR) and normotensive Wistar‐Kyoto (WKY) rats. After arterial pressure and heart rate recordings, phrenic nerves of 20 week‐old male and female SHR and WKY were prepared for epoxy resin embedding and light microscopy. Morphometry was performed with the aid of computer software. Our results showed for male and female SHR remarkable longitudinal asymmetry on both sides and an asymmetry between sides on distal segments, which were not present on WKY nerves. Phrenic nerves were generally larger in males compared to females on both strains but larger on WKY compared to SHR for both genders. Myelinated fiber number and density were significantly larger on females of both groups and remarkably larger on WKY compared to SHR in both genders. Strain and gender differences on phrenic nerve myelinated fiber number is described for the first time in this experimental model of hypertension, pointing to the need for thorough functional studies of this nerve on male and female SHR.Grant Funding Source: FAPESP