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Localization of SSeCKS in unmyelinated primary sensory neurons.

Irmen CP, Siegel SM, Carr PA - J Brachial Plex Peripher Nerve Inj (2008)

Bottom Line: In capsaicin treated rats, SSeCKS immunoreactivity was essentially obliterated in the dorsal horn while in dorsal root ganglia quantitative analysis revealed a 43% reduction in the number of SSeCKS-labeled cells.This attenuation is concomitant with a decrease in fluoride-resistant acid phosphatase labeled fibers in the spinal cord dorsal horn and small neuronal somata in sensory ganglia.These results demonstrate that SSeCKS is primarily localized within a distinct subpopulation of small diameter, largely unmyelinated C-fiber primary sensory neurons putatively involved in nociception.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Anatomy and Cell Biology, University of North Dakota, Grand Forks, ND 58202, USA. cirmen@medicine.nodak.edu

ABSTRACT

Background: SSeCKS (Src SupprEssed C Kinase Substrate) is a proposed protein kinase C substrate/A kinase anchoring protein (AKAP) that has recently been characterized in the rat peripheral nervous system. It has been shown that approximately 40% of small primary sensory neurons contain SSeCKS-immunoreactivity in a population largely separate from substance P (95.2%), calcitonin gene related peptide (95.3%), or fluoride resistant acid phosphatase (55.0%) labeled cells. In the spinal cord, it was found that SSeCKS-immunoreactive axon collaterals terminate in the dorsal third of lamina II outer in a region similar to that of unmyelinated C-, or small diameter myelinated Adelta-, fibers. However, the precise characterization of the anatomical profile of the primary sensory neurons containing SSeCKS remains to be determined. Here, immunohistochemical labeling at the light and ultrastructural level is used to clarify the myelination status of SSeCKS-containing sensory neuron axons and to further clarify the morphometric, and provide insight into the functional, classification of SSeCKS-IR sensory neurons.

Methods: Colocalization studies of SSeCKS with myelination markers, ultrastructural localization of SSeCKS labeling and ablation of largely unmyelinated sensory fibers by neonatal capsaicin administration were all used to establish whether SSeCKS containing sensory neurons represent a subpopulation of unmyelinated primary sensory C-fibers.

Results: Double labeling studies of SSeCKS with CNPase in the dorsal horn and Pzero in the periphery showed that SSeCKS immunoreactivity was observed predominantly in association with unmyelinated primary sensory fibers. At the ultrastructural level, SSeCKS immunoreactivity was most commonly associated with axonal membrane margins of unmyelinated fibers. In capsaicin treated rats, SSeCKS immunoreactivity was essentially obliterated in the dorsal horn while in dorsal root ganglia quantitative analysis revealed a 43% reduction in the number of SSeCKS-labeled cells. This attenuation is concomitant with a decrease in fluoride-resistant acid phosphatase labeled fibers in the spinal cord dorsal horn and small neuronal somata in sensory ganglia.

Conclusion: These results demonstrate that SSeCKS is primarily localized within a distinct subpopulation of small diameter, largely unmyelinated C-fiber primary sensory neurons putatively involved in nociception.

No MeSH data available.


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Micrographs showing SSeCKS-immunoreacted sections of L4 DRG and spinal cord superficial dorsal horn from control and capsaicin-treated rats. (A) In control animals, robust SSeCKS-immunofluorescence is present within Lissauer's tract (LT) and lamina I, II and dorsal lamina III. In the same section of lumbar spinal cord, brightly labeled, rostrocaudally oriented axon bundles are observed ventral to the central canal (Inset A). (B) In capsaicin-injected animals, SSeCKS-immunofluorescence within Lissauer's tract and lamina I, II and III is depleted. In the same section, the intensity and abundance of SSeCKS-labeled axons ventral to the central canal is greatly reduced (Inset B). (C) In ganglia sections from control animals, SSeCKS immunolabeling can be observed in the cytoplasm of small cells and associated with the perimeter of both small and large cells. (D) In ganglia sections from capsaicin-injected animals, a decrease in the number of small cells was quantified along with a corresponding lack of SSeCKS immunolabeling in the cytoplasm of small cells.
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Figure 4: Micrographs showing SSeCKS-immunoreacted sections of L4 DRG and spinal cord superficial dorsal horn from control and capsaicin-treated rats. (A) In control animals, robust SSeCKS-immunofluorescence is present within Lissauer's tract (LT) and lamina I, II and dorsal lamina III. In the same section of lumbar spinal cord, brightly labeled, rostrocaudally oriented axon bundles are observed ventral to the central canal (Inset A). (B) In capsaicin-injected animals, SSeCKS-immunofluorescence within Lissauer's tract and lamina I, II and III is depleted. In the same section, the intensity and abundance of SSeCKS-labeled axons ventral to the central canal is greatly reduced (Inset B). (C) In ganglia sections from control animals, SSeCKS immunolabeling can be observed in the cytoplasm of small cells and associated with the perimeter of both small and large cells. (D) In ganglia sections from capsaicin-injected animals, a decrease in the number of small cells was quantified along with a corresponding lack of SSeCKS immunolabeling in the cytoplasm of small cells.

Mentions: The effect of neonatal capsaicin administration on SSeCKS-IR in adult animals was examined in both transverse spinal cord and sensory ganglia sections. In control animals, SSeCKS-IR was similar to that previously reported [17]. In brief, SSeCKS-IR was observed in putative primary afferent central axonal arbors in Lissauer's tract, lamina I and II, as well as in occasional fibers seen to course ventrally into lamina III and IV. In addition, rostrocaudally oriented SSeCKS-IR fibers were observed both dorsal and ventral to the central canal (lamina X; Fig. 4A inset). Conversely, capsaicin-treated animals demonstrated a distinct diminution of SSeCKS-IR (Fig. 4B). The entire first and second lamina was devoid of SSeCKS-IR fibers with the rare exception of occasional faint, large diameter fibers traversing dorsoventrally through the superficial lamina. In addition, a reduction in SSeCKS-IR was observed in the area dorsal and ventral to the central canal (lamina X) of the spinal cord (Fig. 4B inset). In the dorsal columns (not shown) of capsaicin-injected animals some SSeCKS-IR persisted in apparent massed bundles of axonal processes.


Localization of SSeCKS in unmyelinated primary sensory neurons.

Irmen CP, Siegel SM, Carr PA - J Brachial Plex Peripher Nerve Inj (2008)

Micrographs showing SSeCKS-immunoreacted sections of L4 DRG and spinal cord superficial dorsal horn from control and capsaicin-treated rats. (A) In control animals, robust SSeCKS-immunofluorescence is present within Lissauer's tract (LT) and lamina I, II and dorsal lamina III. In the same section of lumbar spinal cord, brightly labeled, rostrocaudally oriented axon bundles are observed ventral to the central canal (Inset A). (B) In capsaicin-injected animals, SSeCKS-immunofluorescence within Lissauer's tract and lamina I, II and III is depleted. In the same section, the intensity and abundance of SSeCKS-labeled axons ventral to the central canal is greatly reduced (Inset B). (C) In ganglia sections from control animals, SSeCKS immunolabeling can be observed in the cytoplasm of small cells and associated with the perimeter of both small and large cells. (D) In ganglia sections from capsaicin-injected animals, a decrease in the number of small cells was quantified along with a corresponding lack of SSeCKS immunolabeling in the cytoplasm of small cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2277419&req=5

Figure 4: Micrographs showing SSeCKS-immunoreacted sections of L4 DRG and spinal cord superficial dorsal horn from control and capsaicin-treated rats. (A) In control animals, robust SSeCKS-immunofluorescence is present within Lissauer's tract (LT) and lamina I, II and dorsal lamina III. In the same section of lumbar spinal cord, brightly labeled, rostrocaudally oriented axon bundles are observed ventral to the central canal (Inset A). (B) In capsaicin-injected animals, SSeCKS-immunofluorescence within Lissauer's tract and lamina I, II and III is depleted. In the same section, the intensity and abundance of SSeCKS-labeled axons ventral to the central canal is greatly reduced (Inset B). (C) In ganglia sections from control animals, SSeCKS immunolabeling can be observed in the cytoplasm of small cells and associated with the perimeter of both small and large cells. (D) In ganglia sections from capsaicin-injected animals, a decrease in the number of small cells was quantified along with a corresponding lack of SSeCKS immunolabeling in the cytoplasm of small cells.
Mentions: The effect of neonatal capsaicin administration on SSeCKS-IR in adult animals was examined in both transverse spinal cord and sensory ganglia sections. In control animals, SSeCKS-IR was similar to that previously reported [17]. In brief, SSeCKS-IR was observed in putative primary afferent central axonal arbors in Lissauer's tract, lamina I and II, as well as in occasional fibers seen to course ventrally into lamina III and IV. In addition, rostrocaudally oriented SSeCKS-IR fibers were observed both dorsal and ventral to the central canal (lamina X; Fig. 4A inset). Conversely, capsaicin-treated animals demonstrated a distinct diminution of SSeCKS-IR (Fig. 4B). The entire first and second lamina was devoid of SSeCKS-IR fibers with the rare exception of occasional faint, large diameter fibers traversing dorsoventrally through the superficial lamina. In addition, a reduction in SSeCKS-IR was observed in the area dorsal and ventral to the central canal (lamina X) of the spinal cord (Fig. 4B inset). In the dorsal columns (not shown) of capsaicin-injected animals some SSeCKS-IR persisted in apparent massed bundles of axonal processes.

Bottom Line: In capsaicin treated rats, SSeCKS immunoreactivity was essentially obliterated in the dorsal horn while in dorsal root ganglia quantitative analysis revealed a 43% reduction in the number of SSeCKS-labeled cells.This attenuation is concomitant with a decrease in fluoride-resistant acid phosphatase labeled fibers in the spinal cord dorsal horn and small neuronal somata in sensory ganglia.These results demonstrate that SSeCKS is primarily localized within a distinct subpopulation of small diameter, largely unmyelinated C-fiber primary sensory neurons putatively involved in nociception.

View Article: PubMed Central - HTML - PubMed

Affiliation: Dept. of Anatomy and Cell Biology, University of North Dakota, Grand Forks, ND 58202, USA. cirmen@medicine.nodak.edu

ABSTRACT

Background: SSeCKS (Src SupprEssed C Kinase Substrate) is a proposed protein kinase C substrate/A kinase anchoring protein (AKAP) that has recently been characterized in the rat peripheral nervous system. It has been shown that approximately 40% of small primary sensory neurons contain SSeCKS-immunoreactivity in a population largely separate from substance P (95.2%), calcitonin gene related peptide (95.3%), or fluoride resistant acid phosphatase (55.0%) labeled cells. In the spinal cord, it was found that SSeCKS-immunoreactive axon collaterals terminate in the dorsal third of lamina II outer in a region similar to that of unmyelinated C-, or small diameter myelinated Adelta-, fibers. However, the precise characterization of the anatomical profile of the primary sensory neurons containing SSeCKS remains to be determined. Here, immunohistochemical labeling at the light and ultrastructural level is used to clarify the myelination status of SSeCKS-containing sensory neuron axons and to further clarify the morphometric, and provide insight into the functional, classification of SSeCKS-IR sensory neurons.

Methods: Colocalization studies of SSeCKS with myelination markers, ultrastructural localization of SSeCKS labeling and ablation of largely unmyelinated sensory fibers by neonatal capsaicin administration were all used to establish whether SSeCKS containing sensory neurons represent a subpopulation of unmyelinated primary sensory C-fibers.

Results: Double labeling studies of SSeCKS with CNPase in the dorsal horn and Pzero in the periphery showed that SSeCKS immunoreactivity was observed predominantly in association with unmyelinated primary sensory fibers. At the ultrastructural level, SSeCKS immunoreactivity was most commonly associated with axonal membrane margins of unmyelinated fibers. In capsaicin treated rats, SSeCKS immunoreactivity was essentially obliterated in the dorsal horn while in dorsal root ganglia quantitative analysis revealed a 43% reduction in the number of SSeCKS-labeled cells. This attenuation is concomitant with a decrease in fluoride-resistant acid phosphatase labeled fibers in the spinal cord dorsal horn and small neuronal somata in sensory ganglia.

Conclusion: These results demonstrate that SSeCKS is primarily localized within a distinct subpopulation of small diameter, largely unmyelinated C-fiber primary sensory neurons putatively involved in nociception.

No MeSH data available.


Related in: MedlinePlus