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Katelyn N Benthall, Ryan A Hough, Andrew D McClellan
Following spinal cord injury (SCI) in the lamprey, there is virtually complete recovery of locomotion within a few weeks, but interestingly, axonal regeneration of reticulospinal (RS) neurons is mostly limited to short distances caudal to the injury site. To explain this situation, we hypothesize that descending propriospinal (PS) neurons relay descending drive from RS neurons to indirectly activate spinal central pattern generators (CPGs). In the present study, the contributions of PS neurons to locomotor recovery were tested in the lamprey following SCI...
October 19, 2016: Journal of Neurophysiology
Rafael Almeida, David Lyons
Oligodendrocytes form myelin around axons of the central nervous system, enabling saltatory conduction. Recent work has established that axons can regulate certain aspects of oligodendrocyte development and myelination, yet remarkably oligodendrocytes in culture retain the ability to differentiate in the absence of axons and elaborate myelin sheaths around synthetic axon-like substrates. It remains unclear the extent to which the life-course of oligodendrocytes requires the presence of, or signals derived from axons in vivo...
2016: PloS One
Li-Ju Hsu, Pavel V Zelenin, Grigori N Orlovsky, Tatiana G Deliagina
KEY POINTS: Spinal reflexes are substantial components of the motor control system in all vertebrates and centrally driven reflex modifications are essential to many behaviours, but little is known about the neuronal mechanisms underlying these modifications. To study this issue, we took advantage of an in vitro brainstem-spinal cord preparation of the lamprey (a lower vertebrate), in which spinal reflex responses to spinal cord bending (caused by signals from spinal stretch receptor neurons) can be evoked during different types of fictive behaviour...
September 2, 2016: Journal of Physiology
Lorenza Capantini, Arndt von Twickel, Brita Robertson, Sten Grillner
In vertebrates, the pretectum and optic tectum (superior colliculus in mammals) are visuomotor areas that process sensory information and shape motor responses. Whereas the tectum has been investigated in great detail, the pretectum has received far less attention. The present study provides a detailed analysis of the connectivity and neuronal properties of lamprey pretectal cells. The pretectum can be subdivided roughly into three areas based on cellular location and projection pattern: superficial, central, and periventricular...
August 25, 2016: Journal of Comparative Neurology
Constanze Lenschow, Jean-René Cazalets, Sandrine S Bertrand
Activity-dependent synaptic plasticity (ADSP) is paramount to synaptic processing and maturation. However, identifying the ADSP capabilities of the numerous synapses converging onto spinal motoneurons (MNs) remain elusive. Using spinal cord slices from mice at two developmental stages, 1-4 and 8-12 postnatal days (P1-P4; P8-P12), we found that high-frequency stimulation of presumed reticulospinal neuron axons in the ventrolateral funiculus (VLF) induced either an NMDA receptor-dependent-long-term depression (LTD), a short-term depression (STD) or no synaptic modulation in limb MNs...
2016: Scientific Reports
Laurent Juvin, Swantje Grätsch, Emilie Trillaud-Doppia, Jean-François Gariépy, Ansgar Büschges, Réjean Dubuc
Locomotion requires the proper sequencing of neural activity to start, maintain, and stop it. Recently, brainstem neurons were shown to specifically stop locomotion in mammals. However, the cellular properties of these neurons and their activity during locomotion are still unknown. Here, we took advantage of the lamprey model to characterize the activity of a cell population that we now show to be involved in stopping locomotion. We find that these neurons display a burst of spikes that coincides with the end of swimming activity...
June 14, 2016: Cell Reports
Emma J Mitchell, Sarah McCallum, Deborah Dewar, David J Maxwell
[This corrects the article DOI: 10.1371/journal.pone.0152094.].
2016: PloS One
Sigrid Koudelka, Matthew G Voas, Rafael G Almeida, Marion Baraban, Jan Soetaert, Martin P Meyer, William S Talbot, David A Lyons
Regulation of myelination by oligodendrocytes in the CNS has important consequences for higher-order nervous system function (e.g., [1-4]), and there is growing consensus that neuronal activity regulates CNS myelination (e.g., [5-9]) through local axon-oligodendrocyte synaptic-vesicle-release-mediated signaling [10-12]. Recent analyses have indicated that myelination along axons of distinct neuronal subtypes can differ [13, 14], but it is not known whether regulation of myelination by activity is common to all neuronal subtypes or only some...
June 6, 2016: Current Biology: CB
Dimitri Ryczko, Jackson J Cone, Michael H Alpert, Laurent Goetz, François Auclair, Catherine Dubé, Martin Parent, Mitchell F Roitman, Simon Alford, Réjean Dubuc
Dopamine neurons are classically known to modulate locomotion indirectly through ascending projections to the basal ganglia that project down to brainstem locomotor networks. Their loss in Parkinson's disease is devastating. In lampreys, we recently showed that brainstem networks also receive direct descending dopaminergic inputs that potentiate locomotor output. Here, we provide evidence that this descending dopaminergic pathway is conserved to higher vertebrates, including mammals. In salamanders, dopamine neurons projecting to the striatum or brainstem locomotor networks were partly intermingled...
April 26, 2016: Proceedings of the National Academy of Sciences of the United States of America
Jie Chen, Cindy Laramore, Michael I Shifman
After spinal cord injury (SCI) in mammals, injured axons fail to regenerate. By contrast, lampreys recover from complete spinal transection and axons regenerate selectively in their correct paths. Yet the large, identified reticulospinal neurons in the lamprey brain vary greatly in their regenerative abilities - some have high regeneration capacity (probability of regeneration >50%) and others have low regeneration capacity (<30%) - even though they have similar projection paths. The presence of both regenerating and non-regenerating neurons located in the same brain region and projecting to the same axon tracts suggests that differences in their regenerating abilities depend upon factors intrinsic to the neurons...
June 2016: Experimental Neurology
Benjamin M Perlman, Miriam A Ashley-Ross
Aquatic C-start escape responses in teleost fishes are driven by a well-studied network of reticulospinal neurons that produce a motor pattern of simultaneous contraction of axial muscle on the side of the body opposite the threatening stimulus, bending the fish into the characteristic C shape, followed by a traveling wave of muscle contraction on the contralateral side that moves the fish away from the threat. Superficially, the kinematics of the terrestrial tail-flip resemble the C-start, with the anterior body rolling up and over the tail into a tight C shape, followed by straightening as the fish launches off of the caudal peduncle into ballistic flight...
June 15, 2016: Journal of Experimental Biology
Emma J Mitchell, Sarah McCallum, Deborah Dewar, David J Maxwell
Descending systems have a crucial role in the selection of motor output patterns by influencing the activity of interneuronal networks in the spinal cord. Commissural interneurons that project to the contralateral grey matter are key components of such networks as they coordinate left-right motor activity of fore and hind-limbs. The aim of this study was to determine if corticospinal (CST) and reticulospinal (RST) neurons make significant numbers of axonal contacts with cervical commissural interneurons. Two classes of commissural neurons were analysed: 1) local commissural interneurons (LCINs) in segments C4-5; 2) long descending propriospinal neurons (LDPNs) projecting from C4 to the rostral lumbar cord...
2016: PloS One
Ayşegül Gündüz, Meral E Kızıltan, Tülin Coşkun, Şakir Delil, Naz Yeni, Çiğdem Özkara
Rasmussen syndrome is a rare, inflammatory and probably autoimmune disease presenting with epilepsia partialis continua which is generally in the form of myoclonic jerks and involves the upper extremities with or without head involvement. We sought to demonstrate the electrophysiological features in patients with Rasmussen syndrome. We performed continuous electrophysiological recordings of involuntary movement, as well as recordings of startle responses and long latency reflex in three patients with a diagnosis of Rasmussen syndrome...
March 2016: Epileptic Disorders: International Epilepsy Journal with Videotape
Stephanie M Fogerson, Alexandra J van Brummen, David J Busch, Scott R Allen, Robin Roychaudhuri, Susan M L Banks, Frank-Gerrit Klärner, Thomas Schrader, Gal Bitan, Jennifer R Morgan
Spinal cord injury causes neuronal death, limiting subsequent regeneration and recovery. Thus, there is a need to develop strategies for improving neuronal survival after injury. Relative to our understanding of axon regeneration, comparatively little is known about the mechanisms that promote the survival of damaged neurons. To address this, we took advantage of lamprey giant reticulospinal neurons whose large size permits detailed examination of post-injury molecular responses at the level of individual, identified cells...
April 2016: Experimental Neurology
Kathren L Fink, William B J Cafferty
Neurons have a limited capacity to regenerate in the adult central nervous system (CNS). The inability of damaged axons to re-establish original circuits results in permanent functional impairment after spinal cord injury (SCI). Despite abortive regeneration of axotomized CNS neurons, limited spontaneous recovery of motor function emerges after partial SCI in humans and experimental rodent models of SCI. It is hypothesized that this spontaneous functional recovery is the result of the reorganization of descending motor pathways spared by the injury, suggesting that plasticity of intact circuits is a potent alternative conduit to enhance functional recovery after SCI...
April 2016: Neurotherapeutics: the Journal of the American Society for Experimental NeuroTherapeutics
Maria Di Bonito, Jean-Luc Boulland, Wojciech Krezel, Eya Setti, Michèle Studer, Joel C Glover
The genetic mechanisms underlying the developmental and functional specification of brainstem projection neurons are poorly understood. Here, we use transgenic mouse tools to investigate the role of the gene Hoxb1 in the developmental patterning of vestibular projection neurons, with particular focus on the lateral vestibulospinal tract (LVST). The LVST is the principal pathway that conveys vestibular information to limb-related spinal motor circuits and arose early during vertebrate evolution. We show that the segmental hindbrain expression domain uniquely defined by the rhombomere 4 (r4) Hoxb1 enhancer is the origin of essentially all LVST neurons, but also gives rise to subpopulations of contralateral medial vestibulospinal tract (cMVST) neurons, vestibulo-ocular neurons, and reticulospinal (RS) neurons...
November 2015: ENeuro
Nian Yang, Qi-Cheng Qiao, Yu-Hui Liu, Ji-Qiang Zhang, Zhi-An Hu, Jun Zhang
The central noradrenergic system participates in diverse nervous functions. Nevertheless, our knowledge of the action of adrenoceptors in motor regulation is still lacking. Intriguingly, reticulospinal neurons in the caudal pontine reticular nucleus (PnC) receive fairly dense noradrenergic innervation and play an important role in motor control. Here, after demonstrating the expression of α1- and α2-adrenoceptors in the PnC, we found that noradrenaline elicited a post-synaptic effect (inward or outward whole-cell current at -70 mV holding) on PnC reticulospinal neurons...
December 17, 2015: Molecular Neurobiology
E Garcia-Rill, B Luster, S D'Onofrio, S Mahaffey, V Bisagno, F J Urbano
The fact that the pedunculopontine nucleus (PPN) is part of the reticular activating system places it in a unique position to modulate sensory input and fight-or-flight responses. Arousing stimuli simultaneously activate ascending projections of the PPN to the intralaminar thalamus to trigger cortical high-frequency activity and arousal, as well as descending projections to reticulospinal systems to alter posture and locomotion. As such, the PPN has become a target for deep brain stimulation for the treatment of Parkinson's disease, modulating gait, posture, and higher functions...
July 2016: Journal of Neural Transmission
Roberto Leiras, Francisco Martín-Cora, Patricia Velo, Tania Liste, Antonio Canedo
Animals and human beings sense and react to real/potential dangerous stimuli. However, the supraspinal mechanisms relating noxious sensing and nocifensive behavior are mostly unknown. The collateralization and spatial organization of interrelated neurons are important determinants of coordinated network function. Here we electrophysiologically studied medial medullary reticulospinal neurons (mMRF-RSNs) antidromically identified from the cervical cord of anesthetized cats and found that 1) more than 40% (79/183) of the sampled mMRF-RSNs emitted bifurcating axons running within the dorsolateral (DLF) and ventromedial (VMF) ipsilateral fascicles; 2) more than 50% (78/151) of the tested mMRF-RSNs with axons running in the VMF collateralized to the subnucleus reticularis dorsalis (SRD) that also sent ipsilateral descending fibers bifurcating within the DLF and the VMF...
January 1, 2016: Journal of Neurophysiology
Sarah J Stednitz, Briana Freshner, Samantha Shelton, Tori Shen, Donovan Black, Ethan Gahtan
Dopamine signaling is conserved across all animal species and has been implicated in the disease process of many neurological disorders, including Parkinson's disease (PD). The primary neuropathology in PD involves the death of dopaminergic cells in the substantia nigra (SN), an anatomical region of the brain implicated in dopamine production and voluntary motor control. Increasing evidence suggests that the neurotransmitter dopamine may have a neurotoxic metabolic product (DOPAL) that selectively damages dopaminergic cells...
November 2015: Neurotoxicology and Teratology
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