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The Journal of Neuroscience : the... Apr 2012Hindbrain dorsal interneurons that comprise the rhombic lip relay sensory information and coordinate motor outputs. The progenitor dA1 subgroup of interneurons, which is...
Hindbrain dorsal interneurons that comprise the rhombic lip relay sensory information and coordinate motor outputs. The progenitor dA1 subgroup of interneurons, which is formed along the dorsal-most region of the caudal rhombic lip, gives rise to the cochlear and precerebellar nuclei. These centers project sensory inputs toward upper-brain regions. The fundamental role of dA1 interneurons in the assembly and function of these brainstem nuclei is well characterized. However, the precise en route axonal patterns and synaptic targets of dA1 interneurons are not clear as of yet. Novel genetic tools were used to label dA1 neurons and trace their axonal trajectories and synaptic connections at various stages of chick embryos. Using dA1-specific enhancers, two contralateral ascending axonal projection patterns were identified; one derived from rhombomeres 6-7 that elongated in the dorsal funiculus, while the other originated from rhombomeres 2-5 and extended in the lateral funiculus. Targets of dA1 axons were followed at later stages using PiggyBac-mediated DNA transposition. dA1 axons were found to project and form synapses in the auditory nuclei and cerebellum. Investigation of mechanisms that regulate the patterns of dA1 axons revealed a fundamental role of Lim-homeodomain (HD) proteins. Switch in the expression of the specific dA1 Lim-HD proteins Lhx2/9 into Lhx1, which is typically expressed in dB1 interneurons, modified dA1 axonal patterns to project along the routes of dB1 subgroup. Together, the results of this research provided new tools and knowledge to the assembly of trajectories and connectivity of hindbrain dA1 interneurons and of molecular mechanisms that control these patterns.
Topics: Age Factors; Animals; Axons; Basic Helix-Loop-Helix Transcription Factors; Body Patterning; Cell Count; Chick Embryo; Ectodysplasins; Electroporation; Functional Laterality; Gene Expression Regulation, Developmental; Green Fluorescent Proteins; Humans; Interneurons; LIM-Homeodomain Proteins; Nerve Tissue Proteins; PAX2 Transcription Factor; Rhombencephalon; Synapses
PubMed: 22539838
DOI: 10.1523/JNEUROSCI.4231-11.2012 -
Enhanced Network in Corticospinal Tracts after Infused Mesenchymal Stem Cells in Spinal Cord Injury.Journal of Neurotrauma Dec 2022Although limited spontaneous recovery occurs after spinal cord injury (SCI), current knowledge reveals that multiple forms of axon growth in spared axons can lead to...
Although limited spontaneous recovery occurs after spinal cord injury (SCI), current knowledge reveals that multiple forms of axon growth in spared axons can lead to circuit reorganization and a detour or relay pathways. This hypothesis has been derived mainly from studies of the corticospinal tract (CST), which is the primary descending motor pathway in mammals. The major CST is the dorsal CST (dCST), being the major projection from cortex to spinal cord. Two other components often called "minor" pathways are the ventral and the dorsal lateral CSTs, which may play an important role in spontaneous recovery. Intravenous infusion of mesenchymal stem cells (MSCs) provides functional improvement after SCI with an enhancement of axonal sprouting of CSTs. Detailed morphological changes of CST pathways, however, have not been fully elucidated. The primary objective was to evaluate detailed changes in descending CST projections in SCI after MSC infusion. The MSCs were infused intravenously one day after SCI. A combination of adeno-associated viral vector (AAV), which is an anterograde and non-transsynaptic axonal tracer, was injected 14 days after SCI induction. The AAV with advanced tissue clearing techniques were used to visualize the distribution pattern and high-resolution features of the individual axons coursing from above to below the lesion. The results demonstrated increased observable axonal connections between the dCST and axons in the lateral funiculus, both rostral and caudal to the lesion core, and an increase in observable axons in the dCST below the lesion. This increased axonal network could contribute to functional recovery by providing greater input to the spinal cord below the lesion.
Topics: Animals; Pyramidal Tracts; Spinal Cord Injuries; Recovery of Function; Axons; Spinal Cord; Mesenchymal Stem Cells; Nerve Regeneration; Mammals
PubMed: 35611987
DOI: 10.1089/neu.2022.0106 -
The Journal of Comparative Neurology Nov 2009To characterize neuronal pathways that release opioid peptides in the rat dorsal horn, multiple-label immunohistochemistry, confocal microscopy, and computerized...
To characterize neuronal pathways that release opioid peptides in the rat dorsal horn, multiple-label immunohistochemistry, confocal microscopy, and computerized co-localization measures were used to characterize opioid-containing terminals and cells. An antibody that selectively recognized beta-endorphin labeled fibers and neurons in the ventral horn as well as fibers in the lateral funiculus and lamina X, but practically no fibers in the dorsal horn. An anti-enkephalin antibody, which recognized Leu-, Met-, and Phe-Arg-Met-enkephalin, labeled the dorsolateral funiculus and numerous puncta in laminae I-III and V of the dorsal horn. An antibody against Phe-Arg-Met-enkephalin, which did not recognize Leu- and Met-enkephalin, labeled the same puncta. Antibodies against dynorphin and prodynorphin labeled puncta and fibers in laminae I, II, and V, as well as some fibers in the rest of the dorsal horn. Dynorphin and prodynorphin immunoreactivities colocalized in some puncta and fibers, but the prodynorphin antibody additionally labeled cell bodies. There was no co-localization of dynorphin (or prodynorphin) with enkephalin (or Phe-Arg-Met-enkephalin). Enkephalin immunoreactivity did not colocalize with the C-fiber markers calcitonin gene-related peptide (CGRP), substance P, and isolectin B4. In contrast, there was some colocalization of dynorphin and prodynorphin with CGRP and substance P, but not with isolectin B4. Both enkephalin and dynorphin partly colocalized with vesicular glutamate transporter 2, a marker of glutamatergic terminals. The prodynorphin-positive neurons in the dorsal horn were distinct from neurons expressing mu-opioid receptors, neurokinin 1 receptors, and protein kinase C-gamma. These results show that enkephalins and dynorphins are present in different populations of dorsal horn neurons. In addition, dynorphin is present in some C-fibers.
Topics: Animals; Dynorphins; Enkephalins; Fluorescent Antibody Technique; Male; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nerve Fibers, Unmyelinated; Neural Pathways; Neurons; Neurons, Afferent; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Spinal Cord; beta-Endorphin
PubMed: 19711397
DOI: 10.1002/cne.22130 -
Frontiers in Neural Circuits 2014We aimed to explore the cerebellar cortical inputs from two spinocerebellar pathways, the spinal border cell-component of the ventral spinocerebellar tract (SBC-VSCT)...
We aimed to explore the cerebellar cortical inputs from two spinocerebellar pathways, the spinal border cell-component of the ventral spinocerebellar tract (SBC-VSCT) and the dorsal spinocerebellar tract (DSCT), respectively, in the sublobule C1 of the cerebellar posterior lobe. The two pathways were activated by electrical stimulation of the contralateral lateral funiculus (coLF) and the ipsilateral LF (iLF) at lower thoracic levels. Most granule cells in sublobule C1 did not respond at all but part of the granule cell population displayed high-intensity responses to either coLF or iLF stimulation. As a rule, Golgi cells and Purkinje cell simple spikes responded to input from both LFs, although Golgi cells could be more selective. In addition, a small population of granule cells responded to input from both the coLF and the iLF. However, in these cases, similarities in the temporal topography and magnitude of the responses suggested that the same axons were stimulated from the two LFs, i.e., that the axons of individual spinocerebellar neurons could be present in both funiculi. This was also confirmed for a population of spinal neurons located within known locations of SBC-VSCT neurons and dorsal horn (dh) DSCT neurons. We conclude that bilateral spinocerebellar responses can occur in cerebellar granule cells, but the VSCT and DSCT systems that provide the input can also be organized bilaterally. The implications for the traditional functional separation of VSCT and DSCT systems and the issue whether granule cells primarily integrate functionally similar information or not are discussed.
Topics: Action Potentials; Animals; Biophysics; Cats; Cerebellar Cortex; Electric Stimulation; Electroencephalography; Functional Laterality; Nerve Net; Neurons; Spinal Cord; Spinocerebellar Tracts
PubMed: 25386122
DOI: 10.3389/fncir.2014.00128 -
The Journal of Physiology Dec 19811. Extracellular and intracellular recordings were made from dorsal horn neurones sending their axons through the dorsal columns in cats anaesthetized with chloralose...
1. Extracellular and intracellular recordings were made from dorsal horn neurones sending their axons through the dorsal columns in cats anaesthetized with chloralose and paralysed with gallamine triethiodide. 2. Seventeen neurones were injected with horseradish peroxidase through the intracellular micro-electrode, recovered from the histological material and shown to send their axons into the dorsal columns. 3. The cells had axonal conduction velocities of 30--47 ms-1; excitatory receptive fields that usually showed multireceptive characteristics, often including input from sensitive mechanoreceptors in glabrous skin; a third of the sample had a marked subliminal fringe to the excitatory field; inhibitory fields were usually situated proximal to the excitatory field and contiguous with it. 4. The cells were located in laminae III, IV and medial V. Dorsal cells had restricted dendritic trees that ascended in an essentially cylindrical volume of tissue through lamina II and often into I; cells intermediate in depth had more primary dendrites than the others, usually dorsally directed into lamina II, and a more extensive rostro-caudal development; deep, medial cells had dendritic trees that radiated extensively from the cell body but were restricted to the transverse plane. Two cells had axons that ascended the dorsolateral funiculus for a few mm before re-entering the dorsal horn, crossing it and reaching the dorsal columns. Collaterals were given off the axons in the grey matter, in the dorsolateral funiculus and the dorsal columns. 5. The form and function of the neurones are discussed.
Topics: Animals; Axons; Cats; Dendrites; Evoked Potentials; Horseradish Peroxidase; Neural Conduction; Neural Pathways; Neurons; Spinal Cord
PubMed: 7338813
DOI: 10.1113/jphysiol.1981.sp013970 -
The Journal of Clinical Investigation Oct 2015Primary pain and touch sensory neurons not only detect internal and external sensory stimuli, but also receive inputs from other neurons. However, the neuronal derived...
Primary pain and touch sensory neurons not only detect internal and external sensory stimuli, but also receive inputs from other neurons. However, the neuronal derived inputs for primary neurons have not been systematically identified. Using a monosynaptic rabies viruses-based transneuronal tracing method combined with sensory-specific Cre-drivers, we found that sensory neurons receive intraganglion, intraspinal, and supraspinal inputs, the latter of which are mainly derived from the rostroventral medulla (RVM). The viral-traced central neurons were largely inhibitory but also consisted of some glutamatergic neurons in the spinal cord and serotonergic neurons in the RVM. The majority of RVM-derived descending inputs were dual GABAergic and enkephalinergic (opioidergic). These inputs projected through the dorsolateral funiculus and primarily innervated layers I, II, and V of the dorsal horn, where pain-sensory afferents terminate. Silencing or activation of the dual GABA/enkephalinergic RVM neurons in adult animals substantially increased or decreased behavioral sensitivity, respectively, to heat and mechanical stimuli. These results are consistent with the fact that both GABA and enkephalin can exert presynaptic inhibition of the sensory afferents. Taken together, this work provides a systematic view of and a set of tools for examining peri- and extrasynaptic regulations of pain-afferent transmission.
Topics: Afferent Pathways; Animals; Defective Viruses; Efferent Pathways; Enkephalins; Forelimb; GABAergic Neurons; Ganglia, Spinal; Hyperalgesia; Interneurons; Nerve Net; Nerve Tissue Proteins; Neural Conduction; Neurons, Afferent; Neurons, Efferent; Nociception; Nociceptors; Posterior Horn Cells; Presynaptic Terminals; Rabies virus; Sensory Receptor Cells; Skin; Spinal Cord Dorsal Horn; Virus Replication; gamma-Aminobutyric Acid
PubMed: 26426077
DOI: 10.1172/JCI81156 -
The Journal of Comparative Neurology Aug 2006Contact-dependent interactions between EphB receptors and ephrin-B ligands mediate a variety of cell-cell communication events in the developing and mature central... (Comparative Study)
Comparative Study
Contact-dependent interactions between EphB receptors and ephrin-B ligands mediate a variety of cell-cell communication events in the developing and mature central nervous system (CNS). These predominantly repulsive interactions occur at the interface between what are considered to be mutually exclusive EphB and ephrin-B expression domains. We previously used receptor and ligand affinity probes to show that ephrin-B ligands are expressed in the floor plate and within a dorsal region of the embryonic mouse spinal cord, while EphB receptors are present on decussated segments of commissural axons that navigate between these ephrin-B domains. Here we present the generation and characterization of two new monoclonal antibodies, mAb EfB1-3, which recognizes EphB1, EphB2, and EphB3, and mAb efrnB1, which is specific for ephrin-B1. We use these reagents and polyclonal antibodies specific for EphB1, EphB2, EphB3, or ephrin-B1 to describe the spatiotemporal expression patterns of EphB receptors and ephrin-B1 in the vertebrate spinal cord. Consistent with affinity probe binding, we show that EphB1, EphB2, and EphB3 are each preferentially expressed on decussated segments of commissural axons in vivo and in vitro, and that ephrin-B1 is expressed in a dorsal domain of the spinal cord that includes the roof plate. In contrast to affinity probe binding profiles, we show here that EphB1, EphB2, and EphB3 are present on the ventral commissure, and that EphB1 and EphB3 are expressed on axons that compose the dorsal funiculus. In addition, we unexpectedly find that mesenchymal cells, which surround the spinal cord and dorsal root ganglion, express ephrin-B1.
Topics: Animals; Axons; Chick Embryo; Cricetinae; Ephrin-B1; Ephrin-B3; Female; Immunohistochemistry; Mice; Mice, Inbred BALB C; Rats; Rats, Sprague-Dawley; Receptor, EphB2; Receptors, Eph Family; Spinal Cord; Tissue Distribution; Zebrafish
PubMed: 16786562
DOI: 10.1002/cne.21001 -
Developmental Neurobiology Nov 2018Numerous tissue transplantations have demonstrated that otocysts can develop into normal ears in any location in all vertebrates tested thus far, though the pattern of...
Numerous tissue transplantations have demonstrated that otocysts can develop into normal ears in any location in all vertebrates tested thus far, though the pattern of innervation of these transplanted ears has largely been understudied. Here, expanding on previous findings that transplanted ears demonstrate capability of local brainstem innervation and can also be innervated themselves by efferents, we show that inner ear afferents grow toward the spinal cord mostly along existing afferent and efferent fibers and preferentially enter the dorsal spinal cord. Once in the dorsal funiculus of the spinal cord, they can grow toward the hindbrain and can diverge into vestibular nuclei. Inner ear afferents can also project along lateral line afferents. Likewise, lateral line afferents can navigate along inner ear afferents to reach hair cells in the ear. In addition, transplanted ears near the heart show growth of inner ear afferents along epibranchial placode-derived vagus afferents. Our data indicate that inner ear afferents can navigate in foreign locations, likely devoid of any local ear-specific guidance cues, along existing nerves, possibly using the nerve-associated Schwann cells as substrate to grow along. However, within the spinal cord and hindbrain, inner ear afferents can navigate to vestibular targets, likely using gradients of diffusible factors that define the dorso-ventral axis to guide them. Finally, afferents of transplanted ears functionally connect to native hindbrain vestibular circuitry, indicated by eliciting a startle behavior response, and providing excitatory input to specific sets of extraocular motoneurons.
Topics: Afferent Pathways; Animals; Brain Stem; Ear, Inner; Hair Cells, Auditory; Motor Neurons; Neurons, Afferent; Rhombencephalon; Schwann Cells; Spinal Cord
PubMed: 30027559
DOI: 10.1002/dneu.22629 -
Developmental Dynamics : An Official... May 2003The localization of aggrecan and mRNA splice variants of versican in the developing rat central nervous system has been examined by using specific polyclonal antibodies...
The localization of aggrecan and mRNA splice variants of versican in the developing rat central nervous system has been examined by using specific polyclonal antibodies to the nonhomologous glycosaminoglycan attachment regions of these hyaluronan-binding chondroitin sulfate proteoglycans. At embryonic day 16 (E16), aggrecan and versican splice variants containing either or both the alpha-and beta-domains are present in the marginal zone and subplate of the cerebral cortex and in the amygdala, internal capsule, and the optic and lateral olfactory tracts. There is strong staining of versican but not of aggrecan in the hippocampus and dentate gyrus by E19, whereas both aggrecan and alpha-versican are present in the fimbria. At E19, aggrecan is seen throughout the cerebral cortex, whereas the distribution of versican is considerably more limited, being confined essentially to the marginal zone and subplate. At 1 week postnatal, both aggrecan and versican are present in the prospective white matter and in the molecular and granule cell layers of the cerebellum, but neither proteoglycan is seen in the external granule cell layer. alpha- but not beta-versican staining is seen in Purkinje cells, and aggrecan staining of Purkinje cells is also rather minimal. In the spinal cord at E13, aggrecan is present in the dorsal root entry zone, ventral funiculus, mantle layer, and floor plate, as well as in the dorsal root ganglia and ventral roots. However, alpha-versican is confined to the dorsal root entry zone and the ependyma surrounding the spinal canal, and beta-versican is not present in spinal cord parenchyma at this developmental stage, being limited to the surrounding connective tissue. By E19, there are significant amounts of all three proteoglycans in the spinal cord. Aggrecan staining is most intense in the lateral funiculus and the fasciculi gracilis and cuneatus, where alpha-versican staining is also strong. In contrast, beta-versican is seen predominantly in the motor columns. Differences in the localization and temporal expression patterns of these chondroitin sulfate proteoglycans suggest that, like neurocan and phosphacan, they have partially complementary roles during central nervous system development.
Topics: Aggrecans; Animals; Central Nervous System; Chondroitin Sulfate Proteoglycans; Embryo, Mammalian; Extracellular Matrix Proteins; Immunohistochemistry; Lectins, C-Type; Protein Isoforms; Protein Structure, Tertiary; Proteoglycans; Rats; Versicans
PubMed: 12701107
DOI: 10.1002/dvdy.10282 -
Journal of Neurotrauma Feb 2015Deficits in bladder function are complications following spinal cord injury (SCI), severely affecting quality of life. Normal voiding function requires coordinated...
Deficits in bladder function are complications following spinal cord injury (SCI), severely affecting quality of life. Normal voiding function requires coordinated contraction of bladder and urethral sphincter muscles dependent upon intact lumbosacral reflex arcs and integration of descending and ascending spinal pathways. We previously reported, in electrophysiological recordings, that segmental reflex circuit neurons in anesthetized male rats were modulated by a bilateral spino-bulbo-spinal pathway in the mid-thoracic lateral funiculus. In the present study, behavioral measures of bladder voiding reflexes and hematuria (hemorrhagic cystitis) were obtained to assess the correlation of plasticity-dependent recovery to the degree of lateral funiculus sparing and mid-thoracic lesion level. Adult rats received mid-thoracic-level lesions at one of the following severities: complete spinal transection; bilateral dorsal column lesion; unilateral hemisection; bilateral dorsal hemisection; a bilateral lesion of the lateral funiculi and dorsal columns; or a severe contusion. Voiding function and hematuria were evaluated by determining whether the bladder was areflexic (requiring manual expression, i.e., "crede maneuver"), reflexive (voiding initiated by perineal stroking), or "automatic" (spontaneous voiding without caretaker assistance). Rats with one or both lateral funiculi spared (i.e., bilateral dorsal column lesion or unilateral hemisection) recovered significantly faster than animals with bilateral lateral funiculus lesions, severe contusion, or complete transection. Bladder reflex recovery time was significantly slower the closer a transection lesion was to T10, suggesting that proximity to the segmental sensory and sympathetic innervation of the upper urinary tract (kidney, ureter) should be avoided in the choice of lesion level for SCI studies of micturition pathways. In addition, hematuria duration was significantly longer in males, compared to females, despite similar bladder reflex onset times. We conclude that the sparing of the mid-thoracic lateral funiculus on one side is required for early recovery of bladder reflex voiding function and resolution of hematuria.
Topics: Animals; Disease Models, Animal; Female; Hematuria; Male; Rats; Rats, Wistar; Recovery of Function; Reflex; Spinal Cord Injuries; Urinary Bladder; Urination
PubMed: 25137571
DOI: 10.1089/neu.2013.3247