Dorsal root neurons

Sensory neurons nodose dorsal root neurons... 

After 12-14 hours of exposure of rats to a relatively small amount of metallic mercury vapor (0.55 mg/m3), accumulation of mercury was observed within all cell types examined (ganglion cells, satellite cells, fibroblasts, and macrophages). Mercury has also been detected in dorsal root neurons and satellite cells of primates exposed for one year to mercury through amalgams in dental fillings or the maxillary bone (Danscher et al. 1990). 

Recent data from an in vitro study suggest that mercuric mercury may be more effective than methyl-mercury in some paradigms. Using patch-clamped dorsal root neurons, Arakawa et al. (1991) showed augmentation of the GABA-activated chloride current at extremely low mercuric chloride concentrations (0.1 M), while a 1,000-fold higher concentration of methylmercury showed no such effect. The correlation between these effects observed in vitro and what may be occurring in vivo, however, is not known. 

Andres, R.Y., Jeng, I. and Bradshaw, R.A. (1977) Nerve growth factor receptors identification of distinct classes in plasma membranes and nuclei of embryonic dorsal root neurons. Proc. Natl. Acad. Sci. USA 74 2785-2789. 

These are a subset of sensory neurons having their cell bodies (small to medium size) in dorsal root and in cranial nerve ganglia and possessing nonmyelinated (C-type) or thinly myelinated (A-delta type) fibres. This subset of neurons express transient receptor potential vanilloid type 1 (TRPV1, or vanilloid, or capsaicin receptor) that is excited by capsaicin, the pungent ingredient of chilli. These neurons have been classified as polymodal nociceptors because they can be excited by various noxious stimuli. 

TRPVl, also known as the capsaicin- or vanilloid-receptor, is a nonselective cation channel expressed e.g., in neurons of the dorsal root and trigeminal ganglions, which integrates multiple pain-producing stimuli including heat, protons, capsaicin, and resiniferatoxin. In addition, TRPVl currents can be activated by ananda-mide, protein kinase C (PKC), and by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2). 

Fig. 4.4 Simplified hypothesis of the mechanism of gpI20-induced dorsal root gangUon (DRG) neurotoxicity. CXCR4 binding on Schwann cells by SDF-Ia or gpI20 results in the release of RANTES, which induces tumor necrosis factor (TNF)-a production by DRG neurons, and subsequent TNFRl-mediated neurotoxicity in an autocrine/paracrine fashion. Reproduced with permission of John Wiley Sons, Inc. (Keswani et al. 2003b)...

White FA, Sun J et al (2005b) Excitatory monocyte chemoattractant protein-1 signaling is up-regulated in sensory neurons after chronic compression of the dorsal root ganglion. Proc Natl Acad Sci USA 102(39) 14092-14097... 

Zhu Y, Jones G et al (2005) Lentivirus infection causes neuroinflammation and neuronal injury in dorsal root ganglia pathogenic effects of STAT-1 and inducible nitric oxide synthase. J Immunol 175(2) 1118-1126... 

Zhu Y, Antony J et al (2006) CD8-t lymphocyte-mediated injury of dorsal root ganghon neurons during lentiviras infection CD 154-dependent ceU contact neurotoxicity. J Neurosci 26(13) 3396-3403 Zhu Y, Antony JM et al (2007) Didanosine causes sensory neuropathy in an HIV/AIDS animal model impaired mitochondrial and neurotrophic factor gene expression. Brain 130(Pt 8) 2011-2023... 

Fig. 9.4 Upregulation of MCPl and CCR2 expression in neurons of the dorsal root ganglia in association with the development of neuropathic pain. Upper panels illustrate expression of CCR2 receptors by in situ hybridization in naive rats (a) and animals subjected to Chronic Compression of the DRG (CCD) a model for neuropathic pain (b). CCR2 is expressed in small sateUite cells and many neurons (white arrows). Bottom panels (c, d) illustrate the expression of MCP-1 (immu-nohistochemistry, red) under the same circumstances. Many neurons (red arrows) express the chemokine (From White et al. 2005)...

Jung H, Toth PT, White FA, Miller RJ (2008) Monocyte chemoattractant protein-1 functions as a neuromodulator in dorsal root ganglia neurons. J Neurochem 104 254-263... 

Westmoreland SV, Rottman JB, Williams KC, Lackner AA, Sasseville VG (1998) Chemokine receptor expression on resident and inflammatory cells in the brain of macaques with simian immunodeficiency virus encephalitis. Am J Pathol 152 659-665 White FA, Sun J, Waters SM, Ma C, Ren D, Ripsch M, Steflik J, Cortiight DN, Lamotte RH, Miller RJ (2005) Excitatory monocyte chemoattractant protein-1 signaling is up-regulated in sensory neurons after chronic compression of the dorsal root ganglion. Proc Natl Acad Sci USA 102 14092-14097... 

Jung H, Toth PT, White PA, Miller RJ (2008) Monocyte chemoattractant protein-1 functions as a neuromodulator in dorsal root ganglia neurons. J Neurochem 104 254-263 Kahn L, Alonso G, Normand E, Manzoni OJ (2005) Repeated morphine treatment alters polysia-lylated neural cell adhesion molecule, glutamate decarboxylase-67 expression and ceU proliferation in the adult rat hippocampus. Em J Nemosci 21 493-500 Kaul M, Ma Q, Medders KE, Desai MK, Lipton SA (2007) HIV-1 coreceptors CCR5 and CXCR4 both mediate neuronal cell death but CCR5 paradoxically can also contribute to protection. Cell Death Differ (2) 296-305... 

Zhang N, Rogers TJ, Caterina M, Oppenheim JJ (2004) Proinflammatory chemokines, such as C-C chemokine hgand 3, desensitize mu-opioid receptors on dorsal root ganglia neurons. J Immunol 173 594-599... 

The neurons from which NTs are released number more than 7 billion in the human brain. Each (Fig. 1.2) consists of a cell body, the soma or perikaryon, with one major cytoplasmic process termed the axon, which projects variable distances to other neurons, e.g. from a cortical pyramidal cell to adjacent cortical neurons, or to striatal neurons or to spinal cord motoneurons. Thus by giving off a number of branches from its axon one neuron can influence a number of others. All neurons, except primary sensory neurons with cell bodies in the spinal dorsal root ganglia, have a number of other, generally shorter, projections running much shorter distances among neighbouring neurons like the branches of a tree. These processes are the dendrites. Their... 

The large diameter A/l-afferent fibre enters the dorsal horn of the spinal cord through the medial division of the dorsal root. It then descends through the medial region of lamina I or II, or alternatively, curves around the medial (central) edge of the dorsal horn down to the ventral horn. On reaching deeper laminae, laminae IV and V, the AjS-fibres ascend back up into laminae III and IV where they repeatedly subdivide and form a characteristic termination pattern. The densest arborisation appears to occur in lamina III. Axons originating from specialised muscle stretch receptors have collaterals that pass ventrally to make monosynaptic connections with neurons of laminae V, VI and VII. Some also extend to laminae VIII and IX of the ventral horn where they synapse directly onto motor neurons and form the basis of monosynaptic reflexes. 

Hydrogen ions accumulate in tissue damaged by inflammation and ischaemia and so pH is lowered. These protons may activate nociceptors directly via their own family of ion channels as well as sensitising them to mechanical stimulation. Acid-sensing ion channels (ASICS) are a family of sodium channels that are activated by protons — of special interest is one type found only in small dorsal root ganglion neurons that possibly are responsible for activation of nociceptors. Although the transduction of mechanical stimuli is poorly understood, ASICs are closely related to channels that respond to stretch. 

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