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Peripheral Sensory Neurons (peripheral + sensory_neuron)
Selected AbstractsIn vivo dynamics of CNS sensory arbor formation: A time-lapse study in the embryonic leechDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2003Michael W. Baker Abstract In the embryo of the leech Hirudo medicinalis, afferent projections of peripheral sensory neurons travel along common nerve tracts to the CNS, where they defasciculate, branch, and arborize into separate, modality-specific synaptic laminae. Previous studies have shown that this process requires, at least in part, the constitutive and then modality-specific glycosylations of tractin, a leech L1 homologue. We report here on the dynamics of growth of these projections as obtained by examining the morphology of single growing dye-filled sensory afferents as a function of time. Using 2-photon laser-scanning microscopy of the intact developing embryo, we obtained images of individual sensory projections at 3 to 30 min intervals, over several hours of growth, and at different stages of development. The time-lapse series of images revealed a highly dynamic and maturation-state-dependent pattern of growth. Upon entering the CNS, the growth cone-tipped primary axon sprouted numerous long filopodial processes, many of which appeared to undergo repeated cycles of extension and retraction. The growth cone was transformed into a sensory arbor through the formation of secondary branches that extended within the ganglionic neuropil along the anterior-posterior axis of the CNS. Numerous tertiary and quaternary processes grew from these branches and also displayed cycles of extension and retraction. The motility of these higher-order branches changed with age, with younger afferents displaying higher densities and greater motility than older, more mature sensory arbors. Finally, coincident with a reduction in higher order projections was the appearance of concavolar structures on the secondary processes. Rows of these indentations suggest the formation of presynaptic en-passant specializations accompanying the developmental onset of synapse formation. © 2003 Wiley Periodicals, Inc. J Neurobiol 56: 41,53, 2003 [source] Painful neuropathy alters the effect of gabapentin on sensory neuron excitability in ratsACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 4 2004A. Kanai Background:, Pain following peripheral nerve injury is associated with increased excitability of sensory neurons. Gabapentin (GBP), a novel anticonvulsant with an uncertain mechanism of action, is an effective treatment for neuropathic pain. We therefore investigated the effect of GBP on dorsal root ganglion (DRG) neurons from normal rats and those with painful peripheral nerve injury. Methods:, Dorsal root ganglions were excised from rats with neuropathic pain behaviour following chronic constriction injury (CCI) of the sciatic nerve, and from normal rats. Intercellular recordings were made from myelinated sensory neuron somata using a microelectrode technique from DRGs bathed in artificial CSF with or without GBP (100 µM). Results:, Compared with normal neurons, injury decreased the refractory interval (RI) for repeat action potential (AP) generation increased the number of APs during sustained depolariza- tion, and shortened the after hyperpolarization following an AP. In normal neurons, GBP decreased the RI and increased the AP number during sustained depolarization. In an opposite fashion, the result of GBP application to injured neurons was a decreased number of APs during depolarization and no change in RI. In injured neurons only, GBP increased the time-to-peak for AP depolarization. Conclusions:, Nerve injury by CCI is associated with increased sensory neuron excitability, associated with a decreased AHP. In normal peripheral sensory neurons, GBP has pro-excitatory effects, whereas GBP decreases excitability in injured neurons, possibly on the basis of altered sodium channel function. [source] Molecular determinants of the face map development in the trigeminal brainstemTHE ANATOMICAL RECORD : ADVANCES IN INTEGRATIVE ANATOMY AND EVOLUTIONARY BIOLOGY, Issue 2 2006Reha S. Erzurumlu Abstract The perception of external sensory information by the brain requires highly ordered synaptic connectivity between peripheral sensory neurons and their targets in the central nervous system. Since the discovery of the whisker-related barrel patterns in the mouse cortex, the trigeminal system has become a favorite model for study of how its connectivity and somatotopic maps are established during development. The trigeminal brainstem nuclei are the first CNS regions where whisker-specific neural patterns are set up by the trigeminal afferents that innervate the whiskers. In particular, barrelette patterns in the principal sensory nucleus of the trigeminal nerve provide the template for similar patterns in the face representation areas of the thalamus and subsequently in the primary somatosensory cortex. Here, we describe and review studies of neurotrophins, multiple axon guidance molecules, transcription factors, and glutamate receptors during early development of trigeminal connections between the whiskers and the brainstem that lead to emergence of patterned face maps. Studies from our laboratories and others' showed that developing trigeminal ganglion cells and their axons depend on a variety of molecular signals that cooperatively direct them to proper peripheral and central targets and sculpt their synaptic terminal fields into patterns that replicate the organization of the whiskers on the muzzle. Similar mechanisms may also be used by trigeminothalamic and thalamocortical projections in establishing patterned neural modules upstream from the trigeminal brainstem. © 2006 Wiley-Liss, Inc. [source] Developmental regulation of neuron-specific P2X3 receptor expression in the rat cochleaTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 2 2005Lin-Chien Huang Abstract ATP-gated ion channels assembled from P2X3 receptor (P2X3R) subunits contribute to neurotransmission and neurotrophic signaling, associated with neurite development and synaptogenesis, particularly in peripheral sensory neurons. Here, P2X3R expression was characterized in the rat cochlea from embryonic day 16 (E16) to adult (P49,56), using RT-PCR and immunohistochemistry. P2X3R mRNA was strongly expressed in the cochlea prior to birth, declined to a minimal level at P14, and was absent in adult tissue. P2X3R protein expression was confined to spiral ganglion neurons (SGN) within Rosenthal's canal of the cochlea. At E16, immunolabeling was detected in the SGN neurites, but not the distal neurite projection within the developing sensory epithelium (greater epithelial ridge). From E18, the immunolabeling was observed in the peripheral neurites innervating the inner hair cells but was reduced by P6. However, from P2,8, immunolabeling of the SGN neurites extended to include the outer spiral bundle fiber tract beneath the outer hair cells. This labeling of type II SGN afferent fiber declined after P8. By P14, all synaptic terminal immunolabeling in the organ of Corti was absent, and SGN cell body labeling was minimal. In adult cochlear tissue, P2X3R immunolabeling was not detected. Noise exposure did not induce P2X3R expression in the adult cochlea. These data indicate that ATP-gated ion channels incorporating P2X3R subunit expression are specifically targeted to the afferent terminals just prior to the onset of hearing, and likely contribute to the neurotrophic signaling which establishes functional auditory neurotransmission. J. Comp. Neurol. 484:133,143, 2005. © 2005 Wiley-Liss, Inc. [source] Sporadic onset of erythermalgia: A gain-of-function mutation in Nav1.7ANNALS OF NEUROLOGY, Issue 3 2006Chongyang Han BS Objective Inherited erythermalgia (erythromelalgia) is an autosomal dominant disorder in which patients experience severe burning pain in the extremities, in response to mild thermal stimuli and exercise. Although mutations in sodium channel Nav1.7 have been shown to underlie erythermalgia in several multigeneration families with the disease that have been investigated to date, the molecular basis of erythermalgia in sporadic cases is enigmatic. We investigated the role of Nav1.7 in a sporadic case of erythermalgia in a Chinese family. Methods Genomic DNA from patients and their asymptomatic family members were sequenced to identify mutations in Nav1.7. Whole-cell patch clamp analysis was used to characterize biophysical properties of wild-type and mutant Nav1.7 channels in mammalian cells. Results A single amino acid substitution in the DIIS4-S5 linker of Nav1.7 was present in two children whose parents were asymptomatic. The asymptomatic father was genetically mosaic for the mutation. This mutation produces a hyperpolarizing shift in channel activation and an increase in amplitude of the response to slow, small depolarizations. Interpretation Founder mutations in Nav1.7, which can confer hyperexcitability on peripheral sensory neurons, can underlie sporadic erythermalgia. Ann Neurol 2006 [source] | |||||||||||||