Ultrastructural localization of sympathetic axons in experimental rat sciatic nerve neuromas

Abstract

The ultrastructural localization of sympathetic axons was investigated in normal rat sciatic nerves and experimental sciatic nerve neuromas. The best ultrastructural localization of noradrenaline in the dense-cored vesicles of sympathetic axons was accomplished following pretreatment of rats with nialamide and 5-hydroxy dopamine, followed by fixation according to the modified chromaffin technique of Tranzer and Richards (1976). After such preparation, sympathetic axons containing 5-hydroxy dopamine-labelled dense-cored vesicles could be identified in normal sciatic nerve. Large accumulations of labelled dense-cored vesicles were also found in acute neuromas, up to 1 week after nerve section. Much smaller numbers of dense-cored vesicles could be identified in chronic neuromas from 2 to 3 weeks following nerve section. Sympathetic axons could also be identified following electron probe X-ray microanalysis of the tissue sections, using chromium detection as the marker for the noradrenaline-containing dense-cored vesicles. Unusual configurations of Schwann cell subunits, which enclosed myelinated fibres and sympathetic axon sprouts within the same basal lamina, were identified in the acute neuromas, 3-7 days after nerve section. Such configurations may be of relevance to the pathophysiological interaction which develops between sympathetic efferent and sensory fibres in peripheral nerve neuromas.

Sympathetic sprouting and changes in nociceptive sensory innervation in the glabrous skin of the rat hind paw following partial peripheral nerve injury

“…The sympathetic sprouting became significantly different from sham levels as soon as two weeks post-Iesion. This is a surprising observation, as sorne of the sympathetic fibres travel in the sciatic nerve (Small et al, 1996) and are therefore likely to have been damaged by the lesion. The fact that we did not detect any decrease in the sympathetic innervation would indicate that such a decrease might be masked by a very robust sprouting already significant at 2 weeks and/or that the number of sympathetic fibres traveling in the sciatic nerve is minor compared to that traveling with blood vessels.…”

“…One major difference between the two models is that in the MN model no sympathetic fibres were lesioned, as they do not travel in the MN of the rat (Grelik et al, 2005b), however they do travel in the sciatic nerve (Small et al, 1996). Therefore, if sorne sprouted fibres originate from collaterals ofthose travelling along blood vessels, others are likely regenerated fibres and these have to regrow along the sciatic for a rather long distance (Gloster and Diamond, 1992).…”

C‐fiber (Remak) bundles contain both isolectin B4‐binding and calcitonin gene‐related peptide‐positive axons

“…However, evidence supports the idea that sympathetic axons are interspersed into Remak bundles of the sciatic nerve and not routed separately (Ochoa, 1980). Dense core containing axons (sympathetic axons) can be observed in many of the Remak bundles of sciatic nerve preparations, suggesting that sympathetic axons mix readily with other types of axons in peripheral nerve Remak bundles (Small et al, 1996).…”

Sciatic Nerve of Diabetic Rat Treated With Epoetin Delta: Effects on C-Fibers and Blood Vessels Including Pericytes

“…Animal treatment with nialamide and 5-hydroxy dopamine, for instance, allows identification of sympathetic axons by detecting intra-axonal granular vesicles containing 5-hydroxy dopamine-label, as was observed in rat SN. 40 This study also detected changes (decrease) in the numbers of the granular vesicles in chronic neuromas following nerve section. In the current study, no obvious presence of granular vesicles was noted in the axon profiles positive for TH.…”

“…Although the distribution of CGRP and TH was expected in SN, 9,10,21,24,[39][40][41][42] there have been no previous reports on the distribution of EpoR and IL-3Rb. This study showed that in addition to CGRP and TH, EpoR and IL-3Rb were contained in subpopulations of C-axons in SN of control, diabetic, and epoetin delta-treated rats.…”