Myelinated fiber distribution in the aortic depressor nerve of male and female spontaneously hypertensive rats (728.22)

Abstract

Aortic depressor nerve (ADN) is an afferent nerve that contains myelinated (fast conducting) and unmyelinated (slow conduction) fibers that send information from aortic mechanoreceptors to central nervous system [1]. Previous studies form our laboratory [2,3] in spontaneously hypertensive rats (SHR) have demonstrated morphological alterations on the ADN in SHR, using male and female animals indistinctively. In this study we investigated the ADN fiber distribution comparing male and female adult (20 weeks old) SHR. After the (AP) and heart rate (HR) recordings, together with the ADN spontaneous activity, the left ADN were prepared for light microscopy and morphometry. Myelinated fiber distributions were compared between proximal and distal segments in the same gender and between genders. Myelinated axon and G ratio distributions were also investigated. Myelinated fiber diameter range from 1 to 5 µm, with peak (~40% of fibers) at 2 µm while myelinated axon size range from 0.5 to 4 µm, with peak (~50% of axons) at 1.5 µm. No differences were observed between segments or genders. This indicates that gender does not influence on the ADN myelinated fiber size, allowing the use of male and females for morphological studies. [1] Krieger and Marseillan, Am J Physiol, 1963:205; [2] Fazan et. al, J Auton Nerv Syst 77, 1999:133; [3] Fazan et. al, Am J Physiol Heart Circ Physiol 280,2001:H1560. Grant Funding Source: FAPESP, CAPES, CNPq and FAEPA