Long ascending unmyelinated primary afferent axons in the rat dorsal column: Immunohistochemical localizations

Patterson, Joel T.; Coggeshall, Richard E.; Lee, W. T.; Chung, Kyungsoon

doi:10.1016/0304-3940(90)90697-8

Cited by 58 publications

(29 citation statements)

References 10 publications

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“…From these data, the summed axon counts from the sample pictures were then multiplied by the ratio of the area of the dorsal root to the summed areas of the sample pictures to estimate the total numbers of unmyelinated and noncompact myeli nated axons in the L2 dorsal root. This sampling method has been used in this and other laboratories to estimate axon numbers in peripheral nerves [26] and within fiber tracts in the spinal cord [27][28][29]. In previous studies, we have observed that this sampling method results in an error of less than 2Vo [27,28].…”

Section: Tissue Preparationmentioning

confidence: 97%

Effects of Ethanol Exposure on Myelination and Axon Numbers in the L2 Dorsal Root of the Neonatal Rat

McNeill

Shew²,

Papka³

1991

Dev Neurosci

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Previous studies have demonstrated that exposure to ethanol during development delays the rate at which axons in certain central nervous system tracts acquire myelin. This delay appears to be related to an alteration in oligodendrocyte function and not to an aberrancy in axon size or number. The present study was designed to determine if alteration similar to those observed in the central nervous system also occur in peripheral nerves, specifically the L2 dorsal root. Dams were fed either an ethanol-containing or control liquid diet 2 weeks prior to pregnancy and throughout gestation. The pups born to the pregnant dams were artificially reared from postnatal day (PD) 4 to PD 10 on a similar ethanol-containing or control diet. The pups were sacrificed on PD 10, L2 dorsal roots removed and processed for electron microscopy. The numbers of axons in various states of myelination were quantified. No difference was observed in the number of unmyelinated axons in the L2 dorsal roots from ethanol-exposed and control pups. In roots from ethanol-exposed pups, there was a significant decrease in the number of axons possessing myelin arranged in compact lamellae, but a significant increase in the number of axons surrounded by myelin lamellae in which the Schwann cell cytoplasm had not yet been extruded (noncompact). However, when the number of axons possessing noncompact myelin and a compact myelin sheath were summed, no significant difference was observed. These data suggest that the delay in myelination following ethanol exposure may be a ubiquitous phenomenon throughout the nervous system.

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Section: Tissue Preparationmentioning

confidence: 97%

Effects of Ethanol Exposure on Myelination and Axon Numbers in the L2 Dorsal Root of the Neonatal Rat

McNeill

Shew²,

Papka³

1991

Dev Neurosci

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“…Recent studies provide evidence that a substantial population of thin fibers located in the medial portion of the DF are long, ascending, unmyelinated primary afferent axons transmitting signals of visceral pain (Patterson et al, 1990(Patterson et al, , 1992Hirshberg et al, 1996;Willis et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

The Distribution of Primary Nitric Oxide Synthase- and Parvalbumin- Immunoreactive Afferents in the Dorsal Funiculus of the Lumbosacral Spinal Cord in a Dog

et al. 2007

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1. The aim of the present study was to examine the distribution of unmyelinated, small-diameter myelinated neuronal nitric oxide synthase immunoreactive (nNOS-IR) axons and large-diameter myelinated neuronal nitric oxide synthase and parvalbumin-immunoreactive (PV-IR) axons in the dorsal funiculus (DF) of sacral (S1-S3) and lumbar (L1-L7) segments of the dog.2. nNOS and PV immunohistochemical methods were used to demonstrate the presence of nNOS-IR and PV-IR in the large-diameter myelinated, presumed to be proprioceptive, axons in the DF along the lumbosacral segments.3. Fiber size and density of nNOS-IR and PV-IR axons were used to compartmentalize the DF into five compartments (CI-CV). The first compartment (CI) localized in the lateralmost part of the DF, containing both unmyelinated and small-diameter myelinated nNOS-IR axons, is homologous with the dorsolateral fasciculus, or Lissauer tract. The second compartment (CII) having similar fiber organization as CI is situated more medially in sacral segments. Rostrally, in lower lumbar segments, CII moves more medially, and at upper lumbar level, CII reaches the dorsomedial angle of the DF and fuses with axons of CIV. CIII is the largest in the DF and the only one containing large-diameter myelinated nNOS-IR and PV-IR axons. The largest nNOS-IR and PV-IR axons of CIII (8.0-9.2 mum in diameter), presumed to be stem Ia proprioceptive afferents, are located in the deep portion of the DF close to the dorsal and dorsomedial border of the dorsal horn. The CIV compartment varies in shape, appearing first as a small triangular area in S3 and S2 segments, homologous with the Philippe-Gombault triangle. Beginning at S1 level, CIV acquires a more elongated shape and is seen throughout the lumbar segments as a narrow band of fibers extending just below the dorsal median septum in approximately upper two-thirds of the DF. The CV is located in the basal part of the DF. In general, CV is poor in nNOS-IR fibers; among them solitary PV-IR fibers are seen.4. The analysis of the control material and the degeneration of the large- and medium-caliber nNOS-IR fibers after unilateral L7 and S1 dorsal rhizotomy confirmed that large-caliber nNOS-IR and and PV-IR axons, presumed to be proprioceptive Ia axons, and their ascending and descending collaterals are present in large number in the DF of the lumbosacral intumescence. However, in the DF of the upper lumbar segments, the decrease in the number of nNOS-IR and PV-IR fibers is quite evident.

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“…The first type, which can be referred to as the direct DC pathway, is composed of collaterals of primary afferent fibers whose cell bodies are located in the dorsal root ganglia. These ascending projections include both myelinated and unmyelinated primary afferent fibers that synapse in the dorsal column nuclei (DCN), including the gracile and cuneate nuclei, of the lower medulla (Kuo and De Groat, 1985;Patterson et al, 1990;Garrett et al, 1992; for review see Willis and Coggeshall, 1991). The second type, referred to as the postsynaptic dorsal column (PSDC) pathway, includes the axons of spinal neurons traveling in the dorsal funiculus to terminate synaptically in the DCN (Petit, 1972;Rustioni, 1974Rustioni, , 1976Angaut-Petit, 1975a;Rustioni and Kaufman, 1977;Giesler et al, 1984;Giesler and Cliffer, 1985;Cliffer and Giesler, 1989;Cliffer and Willis, 1994).…”

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confidence: 99%

Ascending projections from the area around the spinal cord central canal: APhaseolus vulgaris leucoagglutinin study in rats

Wang¹,

Willis²,

Westlund³

1999

J. Comp. Neurol.

118

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Long ascending unmyelinated primary afferent axons in the rat dorsal column: Immunohistochemical localizations

Cited by 58 publications

References 10 publications

Effects of Ethanol Exposure on Myelination and Axon Numbers in the L2 Dorsal Root of the Neonatal Rat

Effects of Ethanol Exposure on Myelination and Axon Numbers in the L2 Dorsal Root of the Neonatal Rat

The Distribution of Primary Nitric Oxide Synthase- and Parvalbumin- Immunoreactive Afferents in the Dorsal Funiculus of the Lumbosacral Spinal Cord in a Dog

Ascending projections from the area around the spinal cord central canal: APhaseolus vulgaris leucoagglutinin study in rats

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