Does hypertension affect morphometric parameters of phrenic nerves?

Abstract

We previously reported [1] important differences in phrenic nerve morphology between normotensive Wistar‐Kyoto and spontaneoulsy hypertensive rats (SHR) but the question whether the differences are due to hypertension or intrinsic to the rat strains still remains. We aimed to investigate the phrenic nerve morphology in young normotensive SHR and adult SHR with well established hypertension. Female SHR aged 5 (N=6) or 20 (N=6) weeks were anesthetized for arterial pressure (AP) recording. Proximal and distal segments of the right and left phrenic nerves were removed and prepared for epoxy resin embedding and light microscopy morphometry. Adult rats showed significantly higher body weight and AP, compared to young animals. Phrenic nerves showed morphologic and morphometric lateral and longitudinal symmetry for both groups but were significantly larger on older animals. Myelinated fiber area and diameter were also larger on older animals but their number was not different between groups. Myelinated axons were larger on older animals but the G ratio was not different between groups. As expected, aging affected phrenic nerve fascicle and myelinated fibers size with no alteration in fiber number. Also, hypertension development did not affect morphological parameters considered important for myelinated fiber function.Grant Funding Source : FAPESP, CNPq, CAPES and FAEPA