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The Journal of Comparative Neurology Feb 1997As part of a research program on the evolution of somatosensory systems in vertebrates, the various components of ascending spinal projections were studied with in vivo...
As part of a research program on the evolution of somatosensory systems in vertebrates, the various components of ascending spinal projections were studied with in vivo and in vitro tract-tracing techniques in representative species of amphibians (the large green frog, Rana perezi, the clawed toad, Xenopus laevis and the ribbed newt, Pleurodeles waltl). Three main ascending sensory channels, each with largely separate targets, were demonstrated: 1. Ascending projections via the dorsal funiculus include primary and nonprimary projections that ascend to terminate mainly in the dorsal column nucleus at obex levels. A small component ascends farther rostralwards to terminate in the reticular formation, the octavolateral area, the trigeminal nuclear complex, and in the granular layer of the cerebellum. 2. Projections ascending via the dorsolateral funiculus reach other spinal and supraspinal targets than the dorsal funicular fibers, mainly ipsilaterally. At upper cervical cord and obex levels, many fibers innervate a region considered the amphibian homologue of the lateral cervical nucleus of mammals. In the medulla, these fibers ascend ventral to the descending trigeminal tract to terminate in the dorsal column and the solitary tract nuclei, and more rostrally, in the reticular formation, the descending trigeminal nucleus and the medial aspect of the ventral octaval nucleus. Major projections reach the area between the facial motor nucleus and the ventral octaval nucleus, and a mediolateral subcerebellar band. These projections arise in neurons located mainly in the ipsilateral deep dorsal and lateral fields throughout the spinal cord. 3. Ascending spinal projections via the ventral quadrant of the spinal cord (the ventral and ventrolateral funiculi) ascend throughout the brainstem up to the diencephalon. Along its course, this component innervates various parts of the reticular formation, the octavolateral area, the granular layer of the cerebellum, the region ventromedial and ventrolateral to the isthmic nucleus, and the subcerebellar region. In the mesencephalon, the torus semicircularis, the midbrain tegmentum and, sparsely, the tectum mesencephali are innervated. Beyond the midbrain, various dorsal and particularly ventral thalamic nuclei and the posterior tubercle are innervated by this ascending sensory channel. The cells of origin of some of these projections were observed in the dorsal, and to a lesser extent, in the lateral and ventral spinal fields of the spinal cord. Evidence for the presence of these three main ascending sensory channels throughout vertebrates will be discussed. The presence of such channels appears to be a shared character in the brain of both amniotes and anamniotes.
Topics: Afferent Pathways; Animals; Brain; Ranidae; Salamandridae; Sensation; Spinal Cord; Synaptic Transmission; Xenopus laevis
PubMed: 9120061
DOI: No ID Found -
The Journal of Physiology Sep 19671. The topographic organization of first order afferent fibres in the lumbar, sacral and coccygeal dorsal roots, and in the fasciculus gracilis was studied in squirrel...
1. The topographic organization of first order afferent fibres in the lumbar, sacral and coccygeal dorsal roots, and in the fasciculus gracilis was studied in squirrel monkeys.2. At the entry zone, progressing from caudal to rostral, dorsal root filaments receive fibres from tail and hind-limb receptive fields which serially overlap and describe a spiral-shaped trajectory. The latter starts with tail, progresses post-axially towards the foot, crosses the foot from lateral to medial, and ascends the preaxial leg.3. In the fasciculus gracilis, this arrangement of fibres at the dorsal root entry zone is preserved in its entirety. It assumes the form of a fibre lamination, with the most caudal dorsal root fibres occupying a dorso-medial location; further rostral dorsal root fibres come to lie more ventrolaterally.4. Dorsum and sole of foot project in an overlapping and interdigitating manner to the fibre lamina of the 7th lumber dermatome in the fasciculus gracilis. Thereby, dorsum and sole of foot behave in the projection as if they were one and the same surface.5. The argument is presented that the foot and its projection on to the cross-sectional plane of the dorsal funiculus are topologically equivalent and that the hind-limb as a whole and its projection are not. On the other hand, homotopic mapping of the foot together with the sequential fibre organization in the dorsal funiculus enable many more types of closed curves on the body surface to remain arc-wise connected in the projection than would otherwise be possible.
Topics: Animals; Electrophysiology; Haplorhini; Hindlimb; Neurons; Peripheral Nerves; Skin; Spinal Nerves; Tail
PubMed: 4963874
DOI: 10.1113/jphysiol.1967.sp008292 -
Neuron Dec 2013The spinal cord contains many descending and ascending longitudinal tracts whose development appears to be controlled by distinct guidance systems. We identified a...
The spinal cord contains many descending and ascending longitudinal tracts whose development appears to be controlled by distinct guidance systems. We identified a population of dorsal spinal neurons marked by coexpression of the transcription factor Zic2 and the guidance receptor EphA4. Zic2+;EphA4+ neurons are surrounded by mechanosensory terminals, suggesting innervation by mechanoreceptor afferents. Their axons form an ipsilateral ascending pathway that develops during embryogenesis and projects within the ventral aspect of the dorsal funiculus, the same location as the descending corticospinal tract (CST), which develops postnatally. Interestingly, the same guidance mechanism, namely, ephrinB3-induced EphA4 forward signaling, is required for the guidance of both ascending and descending axon tracts. Our analysis of conditional EphA4 mutant mice also revealed that the development of the dorsal funiculus occurs independently of EphA4 expression in descending CST axons and is linked to the distribution of Zic2+;EphA4+ spinal neurons and the formation of the ascending pathway.
Topics: Animals; Axons; Cell Tracking; Cells, Cultured; Central Nervous System; Embryonic Development; Ephrin-B3; Gene Expression Regulation, Developmental; Interneurons; Mice; Mice, Knockout; Mice, Transgenic; Neural Pathways; Posterior Horn Cells; Receptor, EphA4; Spinal Cord; Transcription Factors
PubMed: 24360544
DOI: 10.1016/j.neuron.2013.10.006 -
The Journal of Physiology Jul 19771. The responses of identified cells in the cat Clarke's column and dorsal horn to micro-electrophoretically applied cholinomimetics and anti-cholinergic substances have...
1. The responses of identified cells in the cat Clarke's column and dorsal horn to micro-electrophoretically applied cholinomimetics and anti-cholinergic substances have been investigated. 2. Both antidromically identified (DSCT neurones) and synaptically activated neurones from the region of the Clarke's column of the spinal cord were excited by ACh. However, the proportion of ACh excited cells was greater in units synaptically activated by ipsilateral dorsolateral funiculus stimulation (78%) than in DSCT neurones (50%). In addition, about 55% of neurones activated either antidromically or synaptically by ipsilateral dorsal column stimulation were excited by ACh. 3. In contrast to a relatively weak excitatory potency on the DSCT neurones (maximum firing frequency did not exceed 130% of the control activated by ipsilateral dorsolateral funiculus stimulation (maximum firing frequency reached 430% of the control level). 4. ACh has a relatively quick and rapidly reversible excitatory effect on Clarke's column neurones and some types of dorsal horn interneurones, which can be obtained also with nicotine. However, the action of nicotine is frequently delayed in onset and recovery. This excitatory action of ACh can be blocked or markedly depressed by dihydro-beta-erythroidine. These results and those obtained with acetyl-beta-methylcholine and atropine seem to suggest that the receptors mediating excitation of the cholinoceptive spinal cells activated either antidromically or synaptically by ipsilateral dorsolateral funiculus stimulation besides predominantly nicotinic have also weak muscarinic properties. 5. Desensitization with repeated applications of ACh and nicotine has been observed in both DSCT neurones and units antidromically activated by ipsilateral dorsal column stimulation. 6. About 11% of units antidromically activated by ipsilateral dorsolateral funiculus stimulation were depressed by ACh. In addition, the depressant effect of ACh was more frequently encountered in the cells unresponsive either to the dorsolateral funiculus or dorsal column stimulation. ACh depression was also seen in units activated either antidromically or synaptically by ipsilateral dorsal column stimulation. In contrast, none of the units synaptically activated by the ipsilateral dorsolateral funiculus stimulation were depressed by ACh. The same was true for spinal neurones receiving convergent peripheral inputs activated either antidromically or synaptically by ipsilateral dorsolateral or dorsal column stimulation. 7. The findings that ACh depression of all tested DSCT neurones is blocked by atropine and readily evoked by acetyl-beta-methylcholine indicates that receptors mediating the effect are of muscarinic type.
Topics: Acetylcholine; Animals; Atropine; Cats; Choline; Dihydro-beta-Erythroidine; Electrophoresis; Evoked Potentials; Female; Interneurons; Male; Methacholine Compounds; Neurons; Nicotine; Spinal Cord
PubMed: 894542
DOI: 10.1113/jphysiol.1977.sp011899 -
The Journal of Physiology Apr 2002Relationships between the morphology of individual neurones of the spinal superficial dorsal horn (SDH), laminae I and II, and their electrophysiological properties were...
Relationships between the morphology of individual neurones of the spinal superficial dorsal horn (SDH), laminae I and II, and their electrophysiological properties were studied in spinal cord slices prepared from anaesthetized, free-ranging hamsters. Tight-seal, whole-cell recordings were made with pipette microelectrodes filled with biocytin to establish electrophysiological characteristics and to label the studied neurones. Neurones were categorized according to location and size of the somata, the dendritic and axonal pattern of arborization, spontaneous synaptic potentials, evoked postsynaptic currents, pattern of discharge to depolarizing pulses and current-voltage relationships. Data were obtained for 170 neurones; 13 of these had somata in lamina I and 157 in lamina II. Stimulation of the segmental dorsal root evoked a prompt excitatory response in almost every neurone sampled (161/166) with nearly 3/4 displaying putative monosynaptic EPSCs. The majority of neurones (133/170) fitted one of several distinctive morphological categories. To a considerable extent, neurones with a common morphological configuration and neurite disposition shared electrophysiological characteristics. Five of the 13 lamina I neurones were relatively large with extensive dendritic arborization in the horizontal dimension and a prominent axon directed ventrally and contralaterally. These presumptive ventrolateral projection neurones differed structurally and electrophysiologically from the other lamina I neurones, which had ipsilateral, locally arborizing axons and/or branches entering the dorsal lateral funiculus. One hundred and twenty lamina II neurones fitted one of five morphological categories: islet, central, medial-lateral, radial or vertical. Central cells were further divided into three groups on functional features. We conclude that the spinal SDH comprises many types of neurones whose morphological characteristics are associated with specific functional features implying diversity in functional organization of the SDH and in its role as a major synaptic termination for thin primary afferent fibres.
Topics: Action Potentials; Animals; Cell Size; Cricetinae; Dendrites; Excitatory Postsynaptic Potentials; Lysine; Patch-Clamp Techniques; Posterior Horn Cells; Staining and Labeling
PubMed: 11927679
DOI: 10.1113/jphysiol.2001.012890 -
IBRO Reports Dec 2020Coordination between the urinary bladder (BL) and external urethral sphincter (EUS) is necessary for storage and elimination of urine. In rats interneuronal circuits at...
Coordination between the urinary bladder (BL) and external urethral sphincter (EUS) is necessary for storage and elimination of urine. In rats interneuronal circuits at two levels of the spinal cord (i.e., L6-S1 and L3-L4) play an important role in this coordination. In the present experiments retrograde trans-synaptic transport of pseudorabies virus (PRV) encoding fluorescent markers (GFP and RFP) was used to trace these circuits. To examine the relative localization of EUS-related and BL-related interneuronal populations we injected PRV-GFP into the EUS and PRV-RFP into the BL wall. The PRV infected populations of spinal interneurons were localized primarily in the dorsal commissure (DCM) of L6/S1 and in a hypothesized lumbar spinal coordinating center (LSCC) in L3/L4 above and lateral to central canal (CC). At both sites colocalization of markers occurred in a substantial number of labeled interneurons indicating concomitant involvement of these double-labelled neurons in the EUS- and BL-circuits and suggesting their role in EUS-BL coordination. Intense GFP or RFP fluorescent was detected in a subpopulation of cells at both sites suggesting that they were infected earlier and therefore likely to represent first order, primary interneurons that directly synapse with output neurons. Larger numbers of weakly fluorescent neurons that likely represent second order interneurons were also identified. Within the population of EUS-related first order interneurons only 3-8 % exhibited positive immunoreaction for an early transcription factor Pax2 specific to GABAergic and glycinergic inhibitory neurons suggesting that the majority of interneurons in DCM and LSCC projecting directly to the EUS motoneurons are excitatory.
PubMed: 32775758
DOI: 10.1016/j.ibror.2020.07.002 -
The Kobe Journal of Medical Sciences Dec 2015Corticospinal tract (CST) neurons are dislocated in the motor cortex of Reelin-deficient mouse, reeler. In the present study, we examined whether postnatal axonal growth...
Corticospinal tract (CST) neurons are dislocated in the motor cortex of Reelin-deficient mouse, reeler. In the present study, we examined whether postnatal axonal growth arising from these dislocated CST neurons are normal or not with use of anterograde tracer, DiI and retrograde tracer, HRP. A single injection of DiI into the motor cortex of the normal and reeler mice was made during postnatal period and 8-24 hours later, the animals were sacrificed to examine DiI-labeled CST axons at the lower medulla and spinal cord. Both in the normal and reeler mice, CST axons arrived at the pyramidal decussation and entered into the contralateral spinal cord around on postnatal day (P) 0.5, and descend in the ventral area of the contralateral dorsal funiculus at C2 level on P2, at C8 level on P3, at the mid-thoracic level on P4, and at the upper lumbar level on P8. The similar results were also demonstrated by the retrograde labeling of CST neurons with injection of HRP into the C1 level or upper lumbar enlargement. Next, we examined CaMKIIα expression in the CST axons of the adult normal and reeler mice. CaMKIIα-immunopositive fibers were recognized throughout the CST pathway from the internal capsule to the dorsal funiculus of the spinal cord both in the normal and reeler mice. The present study has demonstrated that ectopic location of cell bodies of reeler CST neurons do not affect postnatal development of CST axons in the spinal cord.
Topics: Animals; Axons; Biomarkers; Calcium-Calmodulin-Dependent Protein Kinase Type 2; Cell Adhesion Molecules, Neuronal; Extracellular Matrix Proteins; Female; Male; Mice; Mice, Neurologic Mutants; Nerve Tissue Proteins; Pyramidal Tracts; Reelin Protein; Serine Endopeptidases
PubMed: 27323786
DOI: No ID Found -
The Journal of Physiology Dec 19861. In chloralose-anaesthetized cats single-unit micro-electrode recordings were made at the lumbosacral level either from axons in the dorsolateral funiculus and dorsal...
1. In chloralose-anaesthetized cats single-unit micro-electrode recordings were made at the lumbosacral level either from axons in the dorsolateral funiculus and dorsal columns, identified as belonging to the spinocervical tract (s.c.t.) or post-synaptic dorsal column (p.s.d.c.) pathway respectively, or from neurones in the dorsal horn similarly identified. 2. Attempts were made to show that s.c.t. and p.s.d.c. neurones had axons that bifurcated, so that they sent branches into both the ipsilateral dorsolateral funiculus and the dorsal columns. That is, that some, or all, of the presumed s.c.t. or p.s.d.c. axons were common to both populations. In addition, the effects of stimuli applied to the ipsilateral dorsolateral funiculus at C3 and C1 on the resting discharges of p.s.d.c. neurones were examined in order to determine the effectiveness of the link between the s.c.t. and the p.s.d.c. pathway. 3. Thirty-three s.c.t. units (twenty-six axonal recordings and seven soma-dendritic recordings) and thirty p.s.d.c. units (twenty-four axonal and six soma-dendritic recordings) were examined for bifurcating axons by electrically stimulating the dorsolateral funiculus at C3 and the dorsal columns at C4. None of the p.s.d.c. units could be antidromically activated from the ipsilateral dorsolateral funiculus with stimulus strengths up to 40 V or seventy times threshold for antidromic activation from the dorsal columns. Similarly, twenty s.c.t. units could not be activated antidromically from the dorsal columns at stimulus strengths up to 30 V or thirty times threshold for their antidromic excitation from the dorsolateral funiculus. Thirteen s.c.t. units were antidromically activated from the cervical dorsal columns, eight at seventeen or more times threshold for their activation from the dorsolateral funiculus and five at between two and nine times threshold. All s.c.t. units that were activated antidromically from both the cervical dorsal columns and the dorsolateral funiculus showed similar latencies for the two responses. 4. Twenty-five p.s.d.c. units were examined for the effects of ipsilateral dorsolateral funiculus stimulation on their resting activity. In thirteen, clear evidence of facilitatory effects from C3 were observed, whereas similar results were seen in only six of these units when C1 was stimulated and the effects were less. The facilitation had a latency of 3-16 ms and lasted for 6-22 ms. In all but one of the twenty-five units, stimulation at both C1 and C3 produced profound inhibition of the resting discharge that began at between 8 and 26 ms and lasted for up to 300 ms.(ABSTRACT TRUNCATED AT 400 WORDS)
Topics: Action Potentials; Animals; Axons; Cats; Neural Conduction; Neural Pathways; Neurons; Spinal Cord; Time Factors
PubMed: 3625537
DOI: 10.1113/jphysiol.1986.sp016330 -
Acta Neuropathologica Sep 2017Two hallmarks of chronic multiple sclerosis lesions are the absence of significant spontaneous remyelination and primary as well as secondary neurodegeneration. Both...
Two hallmarks of chronic multiple sclerosis lesions are the absence of significant spontaneous remyelination and primary as well as secondary neurodegeneration. Both characteristics may be influenced by the presence of inhibitory factors preventing myelin and neuronal repair. We investigated the potential of antibodies against Nogo-A, a well-known inhibitory protein for neuronal growth and plasticity, to enhance neuronal regeneration and remyelination in two animal models of multiple sclerosis. We induced a targeted experimental autoimmune encephalomyelitis (EAE) lesion in the dorsal funiculus of the cervical spinal cord of adult rats resulting in a large drop of skilled forelimb motor functions. We subsequently observed improved recovery of forelimb function after anti-Nogo-A treatment. Anterograde tracing of the corticospinal tract revealed enhanced axonal sprouting and arborisation within the spinal cord gray matter preferentially targeting pre-motor and motor spinal cord laminae on lesion level and above in the anti-Nogo-A-treated animals. An important additional effect of Nogo-A-neutralization was enhanced remyelination observed after lysolecithin-induced demyelination of spinal tracts. Whereas remyelinated fiber numbers in the lesion site were increased several fold, no effect of Nogo-A-inhibition was observed on oligodendrocyte precursor proliferation, migration, or differentiation. Enhancing remyelination and promoting axonal regeneration and plasticity represent important unmet medical needs in multiple sclerosis. Anti-Nogo-A antibodies hold promise as a potential new therapy for multiple sclerosis, in particular during the chronic phase of the disease when neurodegeneration and remyelination failure determine disability evolution.
Topics: Animals; Antibodies; Axons; Brain; Encephalomyelitis, Autoimmune, Experimental; Female; Inflammation; Nogo Proteins; Rats; Rats, Inbred Lew; Recovery of Function; Remyelination
PubMed: 28646336
DOI: 10.1007/s00401-017-1745-3 -
The Journal of Physiology Apr 2010The specific white matter location of all the spinal pathways conveying penile input to the rostral medulla is not known. Our previous studies using rats demonstrated...
The specific white matter location of all the spinal pathways conveying penile input to the rostral medulla is not known. Our previous studies using rats demonstrated the loss of low but not high threshold penile inputs to medullary reticular formation (MRF) neurons after acute and chronic dorsal column (DC) lesions of the T8 spinal cord and loss of all penile inputs after lesioning the dorsal three-fifths of the cord. In the present study, select T8 lesions were made and terminal electrophysiological recordings were performed 45-60 days later in a limited portion of the nucleus reticularis gigantocellularis (Gi) and Gi pars alpha. Lesions included subtotal dorsal hemisections that spared only the lateral half of the dorsal portion of the lateral funiculus on one side, dorsal and over-dorsal hemisections, and subtotal transections that spared predominantly just the ventromedial white matter. Electrophysiological data for 448 single unit recordings obtained from 32 urethane-anaesthetized rats, when analysed in groups based upon histological lesion reconstructions, revealed (1) ascending bilateral projections in the dorsal, dorsolateral and ventrolateral white matter of the spinal cord conveying information from the male external genitalia to MRF, and (2) ascending bilateral projections in the ventrolateral white matter conveying information from the pelvic visceral organs (bladder, descending colon, urethra) to MRF. Multiple spinal pathways from the penis to the MRF may correspond to different functions, including those processing affective/pleasure/motivational, nociception, and mating-specific (such as for erection and ejaculation) inputs.
Topics: Afferent Pathways; Animals; Electrophysiological Phenomena; Male; Medulla Oblongata; Penis; Pleasure; Rats; Rats, Wistar; Reticular Formation; Spinal Cord; Spinal Cord Injuries; Urinary Bladder
PubMed: 20142271
DOI: 10.1113/jphysiol.2009.186544