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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.


Related in: MedlinePlus

Micrographs demonstrating capsaicin-mediated depletion of a population of primary sensory neurons. (A) FRAP enzyme histochemical reaction product in a section of L4 DRG from a control animal. FRAP reaction product was present within approximately 40% of the small diameter cell bodies. (B) FRAP enzyme histochemical reaction product in a section of L4 DRG from a capsaicin treated animal. The number of somata containing FRAP reaction product was greatly diminished compared to untreated animals (A). (Insets A, B) FRAP enzyme histochemical reaction in transverse sections of L4 spinal cord dorsal horn from control (Inset A) and capsaicin (Inset B) animals. FRAP reaction product was localized within the dorsal third of lamina II of the dorsal horn in control animals and comparatively reduced in capsaicin treated animals. Dorsal is to top. (C) VR-1-immunofluorescence in a section of L4 DRG from a control animal. (D) VR-1-immunofluorescence in a section of L4 DRG from a capsaicin treated animal. The number of somata containing VR-1-immunofluorescence is greatly diminished compared to untreated animals (A). (Insets C, D) VR-1-immunofluorescence in transverse sections of L4 spinal cord dorsal horn from control (Inset C) and capsaicin (Inset D) animals. VR-1 staining was almost completely eliminated following capsaicin treatment.
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Figure 3: Micrographs demonstrating capsaicin-mediated depletion of a population of primary sensory neurons. (A) FRAP enzyme histochemical reaction product in a section of L4 DRG from a control animal. FRAP reaction product was present within approximately 40% of the small diameter cell bodies. (B) FRAP enzyme histochemical reaction product in a section of L4 DRG from a capsaicin treated animal. The number of somata containing FRAP reaction product was greatly diminished compared to untreated animals (A). (Insets A, B) FRAP enzyme histochemical reaction in transverse sections of L4 spinal cord dorsal horn from control (Inset A) and capsaicin (Inset B) animals. FRAP reaction product was localized within the dorsal third of lamina II of the dorsal horn in control animals and comparatively reduced in capsaicin treated animals. Dorsal is to top. (C) VR-1-immunofluorescence in a section of L4 DRG from a control animal. (D) VR-1-immunofluorescence in a section of L4 DRG from a capsaicin treated animal. The number of somata containing VR-1-immunofluorescence is greatly diminished compared to untreated animals (A). (Insets C, D) VR-1-immunofluorescence in transverse sections of L4 spinal cord dorsal horn from control (Inset C) and capsaicin (Inset D) animals. VR-1 staining was almost completely eliminated following capsaicin treatment.

Mentions: Qualitative evaluation of the efficacy of the capsaicin administration was undertaken by comparative examination of FRAP and VR-1 labeling (Fig. 3) in sections of L4 spinal ganglia and transverse sections of L4 spinal cord from un-injected control, pseudocapsaicin-injected control and capsaicin injected animals. Pseudocapsaicin-injected and un-injected controls were comparable by all assessments. In comparison with control animals, capsaicin-injected animals demonstrated a considerable in the number of FRAP labeled small primary sensory neuron somata and central axonal collaterals (Fig. 3A, B). The robust and abundant FRAP labeling observed in small diameter primary sensory somata from control animals (Fig. 3A) was in marked contrast to the relatively limited number of small cells, either unlabeled or containing FRAP reaction product, observed in sections of DRG from capsaicin injected animals (Fig. 3B). In the dorsal horn, the intense band of FRAP reaction product in control animals (Fig. 3A inset) was almost entirely obliterated in animals treated neonatally with capsaicin (Fig. 3B inset).


Localization of SSeCKS in unmyelinated primary sensory neurons.

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

Micrographs demonstrating capsaicin-mediated depletion of a population of primary sensory neurons. (A) FRAP enzyme histochemical reaction product in a section of L4 DRG from a control animal. FRAP reaction product was present within approximately 40% of the small diameter cell bodies. (B) FRAP enzyme histochemical reaction product in a section of L4 DRG from a capsaicin treated animal. The number of somata containing FRAP reaction product was greatly diminished compared to untreated animals (A). (Insets A, B) FRAP enzyme histochemical reaction in transverse sections of L4 spinal cord dorsal horn from control (Inset A) and capsaicin (Inset B) animals. FRAP reaction product was localized within the dorsal third of lamina II of the dorsal horn in control animals and comparatively reduced in capsaicin treated animals. Dorsal is to top. (C) VR-1-immunofluorescence in a section of L4 DRG from a control animal. (D) VR-1-immunofluorescence in a section of L4 DRG from a capsaicin treated animal. The number of somata containing VR-1-immunofluorescence is greatly diminished compared to untreated animals (A). (Insets C, D) VR-1-immunofluorescence in transverse sections of L4 spinal cord dorsal horn from control (Inset C) and capsaicin (Inset D) animals. VR-1 staining was almost completely eliminated following capsaicin treatment.
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Figure 3: Micrographs demonstrating capsaicin-mediated depletion of a population of primary sensory neurons. (A) FRAP enzyme histochemical reaction product in a section of L4 DRG from a control animal. FRAP reaction product was present within approximately 40% of the small diameter cell bodies. (B) FRAP enzyme histochemical reaction product in a section of L4 DRG from a capsaicin treated animal. The number of somata containing FRAP reaction product was greatly diminished compared to untreated animals (A). (Insets A, B) FRAP enzyme histochemical reaction in transverse sections of L4 spinal cord dorsal horn from control (Inset A) and capsaicin (Inset B) animals. FRAP reaction product was localized within the dorsal third of lamina II of the dorsal horn in control animals and comparatively reduced in capsaicin treated animals. Dorsal is to top. (C) VR-1-immunofluorescence in a section of L4 DRG from a control animal. (D) VR-1-immunofluorescence in a section of L4 DRG from a capsaicin treated animal. The number of somata containing VR-1-immunofluorescence is greatly diminished compared to untreated animals (A). (Insets C, D) VR-1-immunofluorescence in transverse sections of L4 spinal cord dorsal horn from control (Inset C) and capsaicin (Inset D) animals. VR-1 staining was almost completely eliminated following capsaicin treatment.
Mentions: Qualitative evaluation of the efficacy of the capsaicin administration was undertaken by comparative examination of FRAP and VR-1 labeling (Fig. 3) in sections of L4 spinal ganglia and transverse sections of L4 spinal cord from un-injected control, pseudocapsaicin-injected control and capsaicin injected animals. Pseudocapsaicin-injected and un-injected controls were comparable by all assessments. In comparison with control animals, capsaicin-injected animals demonstrated a considerable in the number of FRAP labeled small primary sensory neuron somata and central axonal collaterals (Fig. 3A, B). The robust and abundant FRAP labeling observed in small diameter primary sensory somata from control animals (Fig. 3A) was in marked contrast to the relatively limited number of small cells, either unlabeled or containing FRAP reaction product, observed in sections of DRG from capsaicin injected animals (Fig. 3B). In the dorsal horn, the intense band of FRAP reaction product in control animals (Fig. 3A inset) was almost entirely obliterated in animals treated neonatally with capsaicin (Fig. 3B inset).

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