Plasticity of Unmyelinated Fibers in a Side-to-end Tubulization Model.

BACKGROUND: Histomorphometric studies of unmyelinated fibers of the rat fibular nerves are uncommon, and side-to-end neurorrhaphy studies using the fibular nerve investigate primarily motor fibers. We investigated side-to-end tubulization (SET) technique, in which occurs collateral sprouting from the intact donor nerve fibers to the distal stump of receptor nerve, with muscle reinnervation and functional rehabilitation, to assess whether there is a successful growth of unmyelinated fibers in this model. METHODS: Adult Wistar rats fibular nerves were sectioned to create a 5-mm gap. A 6-mm silicone tube was attached between a side of the intact tibial nerve and the sectioned fibular nerve distal stump (SET group), with the left fibular nerve as normal (sham group). Seventy days postsurgery, unmyelinated fibers from the distal segment of the fibular nerve were quantified using light and transmission electron microscopy and their diameters were measured. RESULTS: The number of unmyelinated fibers was similar between sham (1,882 ± 270.9) and SET (2,012 ± 1,060.8), but axons density was significantly greater in the SET (18,733.3 ± 5,668.6) than sham (13,935.0 ± 1,875.8). Additionally, the axonal diameters differed significantly between groups with mean measures in sham (0.968 ± 0.10) > SET (0.648 ± 0.08). CONCLUSIONS: Unmyelinated fiber growth occurred even with a 5-mm distance between the donor and receptor nerves, reaching similar axonal number to the normal nerve, demonstrating that the SET is a reliable technique that can promote a remarkable plasticity of unmyelinated axons.

A histomorphometric study of unmyelinated fibers of the fibular nerve in Wistar rats.

There are few histomorphometric studies on the unmyelinated fibers of the fibular nerve in rats, and the number of experimental studies using this nerve has been increasing in the last years. Sixty-two percent of the endoneurial area from 10 fibular nerves of adult Wistar rats was scanned by electron microscopy, and digitized. The total number of unmyelinated axons (1.882 ± 271) was significantly lesser, and their axon diameters (0.2 µm to 2.8 µm) significantly higher than that determined in previous studies. The histogram peaked at 1 µm. The differences could be due to the nerve sampled area, the number and the age of the animals evaluated, and the laboratory techniques used. This study brings new and referential data to be used in experimental investigations involving histomorphometric evaluation of the rat fibular nerve.

A histomorphometric study of unmyelinated fibers of the fibular nerve in Wistar rats / Histomorfometria das fibras amielínicas do nervo fibular em ratos Wistar

ABSTRACT There are few histomorphometric studies on the unmyelinated fibers of the fibular nerve in rats, and the number of experimental studies using this nerve has been increasing in the last years. Sixty-two percent of the endoneurial area from 10 fibular nerves of adult Wistar rats was scanned by electron microscopy, and digitized. The total number of unmyelinated axons (1.882 ± 271) was significantly lesser, and their axon diameters (0.2 µm to 2.8 µm) significantly higher than that determined in previous studies. The histogram peaked at 1 µm. The differences could be due to the nerve sampled area, the number and the age of the animals evaluated, and the laboratory techniques used. This study brings new and referential data to be used in experimental investigations involving histomorphometric evaluation of the rat fibular nerve.

RESUMO Embora o nervo fibular de ratos venha sendo incluído progressivamente em maior número de estudos experimentais nos últimos anos, há poucos estudos a respeito das suas fibras amielínicas. Os nervos fibulares de 10 ratos Wistar adultos foram avaliados através de microscopia óptica e eletrônica. Varredura sistemática através de microscopia eletrônica de transmissão das áreas fasciculares da porção distal no nervo foi realizada. Em média, 62% da área endoneural foi digitalizada. O número total de axônios amielínicos encontrados (1.882 ± 271) foi significativamente menor e as medidas dos diâmetros axonais (0,2 µm a 2,8 µm) maiores do que o determinado em estudos prévios. O pico do histograma foi constituído por fibras de 1µm. As diferenças podem ser devidas à amostragem de maior área endoneural, ao número e à idade dos animais avaliados, e as técnicas laboratoriais utilizadas. Os dados obtidos podem ser considerados referenciais para o nervo fibular de ratos Wistar adultos.