Differences Exist in the Left and Right Sciatic Nerves of Naïve Rats and Cats

Abstract

The sciatic nerve of rats and cats is commonly used in experimental models of peripheral nerve injury and repair, as well as experiments involving peripheral nerve electrode implantation. In such experiments, morphometric parameters from the implanted nerve are commonly evaluated and compared to control values obtained from the contralateral nerves. However, this may not be an appropriate approach as differences may naturally exist in the structure of the two nerves owing to developmental or behavioral asymmetry. Additionally, in the cat, baseline values for standard morphometric parameters are not well established. In this study, we characterized fascicle area, fiber count, fiber density, fiber packing, mean g-ratio, and fiber diameter distributions in the rat and cat, as well as investigated the potential for naturally occurring sided differences in these parameters in both species. We also investigated whether animal age or location along the nerve influenced these parameters. We found that sided or left/right leg differences exist in some parameters in both the rat and the cat, calling into question the validity of using the contralateral nerve as a control. We also found that animal age and location along the nerve can make significant differences in the parameters tested, establishing the importance of using control nerves from age-and behaviorally matched animals whose morphometric parameters are collected and compared from the same location. Anat Rec, 298:1492Rec, 298: -1501Rec, 298: , 2015. V C 2015 Wiley Periodicals, Inc.

A <inline-formula><tex-math>$\mu$</tex-math></inline-formula>m-Scale Computational Model of Magnetic Neural Stimulation in Multifascicular Peripheral Nerves

“…Additionally, we used this study's statistical parameterization of the axonal characteristics (distributions of the axonal diameters, axonal densities, and g-ratios) to populate fascicles with axons. Although we have only utilized the histological image found in [31], the fascicular arrangement is similar to that shown in another study [32]. The resulting computational model preserves the cross-sectional areas and boundary locations of the fascicles within the nerve, as illustrated in Figure 1…”

“…To incorporate the random distribution of axons inside the fascicles, the axons were randomly positioned and their diameters from 4 to 16 µm were randomly assigned ( Figure 1(c)) based on the fiber distribution data presented in [31]. This achieved a high packing density of 67% or ∼11,000 axons/mm 2 [31], [36].…”

“…This achieved a high packing density of 67% or ∼11,000 axons/mm 2 [31], [36]. For this distribution, the g-ratio (= inner diameter of the axon outer diameter of the axon ) ranged from 0.45 to 0.7 [31]. To create the 3-dimensional (3-D) nerve model, the cross-sectional model was extruded in the x-direction (along the nerve).…”

“…Therefore, the effect of nonlinear membrane conductance on the stimulus current is small and was dismissed for the computation of the stimulus current. Rat sciatic nerves primarily consist of myelinated fibers [31], [36]. Multiple models have been proposed to simulate the behavior of the myelinated axon for electrical neural stimulation [38], [40], [42]- [44].…”

“…To make an accurate prediction of stimulation thresholds, we employed an anatomically-driven computational model that included densely packed fascicles with statistically distributed axon diameters. As the basis for this computational model, we used the histological image of the cross-section of a rat's sciatic nerve from a previous study (Figure 3d of [31]). Additionally, we used this study's statistical parameterization of the axonal characteristics (distributions of the axonal diameters, axonal densities, and g-ratios) to populate fascicles with axons.…”