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Elzbieta Jankowska - One of the best experts on this subject based on the ideXlab platform.
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Interactions between spinal interneurons and Ventral Spinocerebellar Tract neurons.
The Journal of physiology, 2013Co-Authors: Elzbieta Jankowska, Ingela HammarAbstract:Recent evidence indicates that Ventral Spinocerebellar Tract (VSCT) neurons do not merely receive information provided by spinal interneurons but may also modulate the activity of these interneurons. Hence, interactions between them may be mutual. However, while it is well established that spinal interneurons may provide both excitatory and inhibitory input to ascending Tract neurons, the functional consequences of the almost exclusively inhibitory input from premotor interneurons to subpopulations of VSCT neurons were only recently addressed. These are discussed in the first part of this review. The second part of the review summarizes evidence that some VSCT neurons may operate both as projection neurons and as spinal inter- neurons and play a role in spinal circuitry. It outlines the evidence that initial axon collaterals of VSCT neurons target premotor inhibitory interneurons in disynaptic reflex pathways from tendon organs and muscle spindles (group Ia, Ib and/or II muscle afferents) to motoneurons. By activating these interneurons VSCT neurons may evoke disynaptic IPSPs in motoneurons and thus facilitate inhibitory actions of contralateral muscle afferents on motoneurons. In this way they may contribute to the coordination between neuronal networks on both sides of the spinal cord in advance of modulatory actions evoked via the cerebellar control systems.
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A survey of spinal collateral actions of feline Ventral Spinocerebellar Tract neurons
The European journal of neuroscience, 2012Co-Authors: Pierre Geborek, E. Nilsson, Francesco Bolzoni, Elzbieta JankowskaAbstract:The aim of this study was to identify spinal target cells of Spinocerebellar neurons, in particular the Ventral Spinocerebellar Tract (VSCT) neurons, giving off axon collaterals terminating within the lumbosacral enlargement. Axons of Spinocerebellar neurons were stimulated within the cerebellum while searching for most direct synaptic actions on intracellularly recorded hindlimb motoneurons and interneurons. In motoneurons the dominating effects were inhibitory [inhibitory postsynaptic potentials (IPSPs) in 67% and excitatory postsynaptic potentials (EPSPs) in 17% of motoneurons]. Latencies of most IPSPs indicated that they were evoked disynaptically and mutual facilitation between these IPSPs and disynaptic IPSPs evoked by group Ia afferents from antagonist muscles and group Ib and II afferents from synergists indicated that they were relayed by premotor interneurons in reflex pathways from muscle afferents. Monosynaptic EPSPs from the cerebellum were accordingly found in Ia inhibitory interneurons and intermediate zone interneurons with input from group I and II afferents but only oligosynaptic EPSPs in motoneurons. Monosynaptic EPSPs following cerebellar stimulation were also found in some VSCT neurons, indicating coupling between various Spinocerebellar neurons. The results are in keeping with the previously demonstrated projections of VSCT neurons to the contralateral Ventral horn, showing that VSCT neurons might contribute to motor control at a spinal level. They might thus play a role in modulating spinal activity in advance of any control exerted via the cerebellar loop.
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INHIBITORY INPUTS TO FOUR TYPES OF Spinocerebellar Tract NEURONS IN THE CAT SPINAL CORD
Neuroscience, 2012Co-Authors: S. Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:Spinocerebellar Tract neurons are inhibited by various sources of input via pathways activated by descending Tracts as well as peripheral afferents. Inhibition may be used to modulate transmission of excitatory information forwarded to the cerebellum. However it may also provide information on the degree of inhibition of motoneurons and on the operation of inhibitory premotor neurons. Our aim was to extend previous comparisons of morphological substrates of excitation of Spinocerebellar neurons to inhibitory input. Contacts formed by inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter, glutamic acid decarboxylase and gephyrin. Quantitative analysis revealed the presence of much higher proportions of inhibitory contacts when compared with excitatory contacts on spinal border (SB) neurons. However similar proportions of inhibitory and excitatory contacts were associated with Ventral Spinocerebellar Tract (VSCT) and dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and the dorsal horn (dhDSCT). In all of the cells, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal versus distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. Variations in the density and distribution of inhibitory contacts found in this study may reflect differences in information on inhibitory processes forwarded by subtypes of Spinocerebellar Tract neurons to the cerebellum.
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Excitatory inputs to four types of Spinocerebellar Tract neurons in the cat and the rat thoraco-lumbar spinal cord.
The Journal of physiology, 2012Co-Authors: Sony Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:The cerebellum receives information from the hindlimbs through several populations of Spinocerebellar Tract neurons. Although the role of these neurons has been established in electrophysiological experiments, the relative contribution of afferent fibres and central neurons to their excitatory input has only been estimated approximately so far. Taking advantage of differences in the immunohistochemistry of glutamatergic terminals of peripheral afferents and of central neurons (with vesicular glutamate transporters VGLUT1 or VGLUT2, respectively), we compared sources of excitatory input to four populations of Spinocerebellar neurons in the thoraco-lumbar spinal cord: dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and in the dorsal horn (dhDSCT) and Ventral Spinocerebellar Tract (VSCT) neurons including spinal border (SB) neurons. This was done on 22 electrophysiologically identified intracellularly labelled neurons in cats and on 80 neurons labelled by retrograde transport of cholera toxin b subunit injected into the cerebellum of rats. In both species distribution of antibodies against VGLUT1 and VGLUT2 on SB neurons (which have dominating inhibitory input from limb muscles), revealed very few VGLUT1 contacts and remarkably high numbers of VGLUT2 contacts. In VSCT neurons with excitatory afferent input, the number of VGLUT1 contacts was relatively high although VGLUT2 contacts likewise dominated, while the proportions of VGLUT1 and VGLUT2 immunoreactive terminals were the reverse on the two populations of DSCT neurons. These findings provide morphological evidence that SB neurons principally receive excitatory inputs from central neurons and provide the cerebellum with information regarding central neuronal activity.
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Collateral Actions of Premotor Interneurons on Ventral Spinocerebellar Tract Neurons in the Cat
Journal of neurophysiology, 2010Co-Authors: Elzbieta Jankowska, Piotr Krutki, Ingela HammarAbstract:Strong evidence that premotor interneurons provide Ventral Spinocerebellar Tract (VSCT) neurons with feedback information on their actions on motoneurons was previously found for Ia inhibitory inte...
Ingela Hammar - One of the best experts on this subject based on the ideXlab platform.
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Interactions between spinal interneurons and Ventral Spinocerebellar Tract neurons.
The Journal of physiology, 2013Co-Authors: Elzbieta Jankowska, Ingela HammarAbstract:Recent evidence indicates that Ventral Spinocerebellar Tract (VSCT) neurons do not merely receive information provided by spinal interneurons but may also modulate the activity of these interneurons. Hence, interactions between them may be mutual. However, while it is well established that spinal interneurons may provide both excitatory and inhibitory input to ascending Tract neurons, the functional consequences of the almost exclusively inhibitory input from premotor interneurons to subpopulations of VSCT neurons were only recently addressed. These are discussed in the first part of this review. The second part of the review summarizes evidence that some VSCT neurons may operate both as projection neurons and as spinal inter- neurons and play a role in spinal circuitry. It outlines the evidence that initial axon collaterals of VSCT neurons target premotor inhibitory interneurons in disynaptic reflex pathways from tendon organs and muscle spindles (group Ia, Ib and/or II muscle afferents) to motoneurons. By activating these interneurons VSCT neurons may evoke disynaptic IPSPs in motoneurons and thus facilitate inhibitory actions of contralateral muscle afferents on motoneurons. In this way they may contribute to the coordination between neuronal networks on both sides of the spinal cord in advance of modulatory actions evoked via the cerebellar control systems.
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INHIBITORY INPUTS TO FOUR TYPES OF Spinocerebellar Tract NEURONS IN THE CAT SPINAL CORD
Neuroscience, 2012Co-Authors: S. Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:Spinocerebellar Tract neurons are inhibited by various sources of input via pathways activated by descending Tracts as well as peripheral afferents. Inhibition may be used to modulate transmission of excitatory information forwarded to the cerebellum. However it may also provide information on the degree of inhibition of motoneurons and on the operation of inhibitory premotor neurons. Our aim was to extend previous comparisons of morphological substrates of excitation of Spinocerebellar neurons to inhibitory input. Contacts formed by inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter, glutamic acid decarboxylase and gephyrin. Quantitative analysis revealed the presence of much higher proportions of inhibitory contacts when compared with excitatory contacts on spinal border (SB) neurons. However similar proportions of inhibitory and excitatory contacts were associated with Ventral Spinocerebellar Tract (VSCT) and dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and the dorsal horn (dhDSCT). In all of the cells, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal versus distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. Variations in the density and distribution of inhibitory contacts found in this study may reflect differences in information on inhibitory processes forwarded by subtypes of Spinocerebellar Tract neurons to the cerebellum.
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Excitatory inputs to four types of Spinocerebellar Tract neurons in the cat and the rat thoraco-lumbar spinal cord.
The Journal of physiology, 2012Co-Authors: Sony Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:The cerebellum receives information from the hindlimbs through several populations of Spinocerebellar Tract neurons. Although the role of these neurons has been established in electrophysiological experiments, the relative contribution of afferent fibres and central neurons to their excitatory input has only been estimated approximately so far. Taking advantage of differences in the immunohistochemistry of glutamatergic terminals of peripheral afferents and of central neurons (with vesicular glutamate transporters VGLUT1 or VGLUT2, respectively), we compared sources of excitatory input to four populations of Spinocerebellar neurons in the thoraco-lumbar spinal cord: dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and in the dorsal horn (dhDSCT) and Ventral Spinocerebellar Tract (VSCT) neurons including spinal border (SB) neurons. This was done on 22 electrophysiologically identified intracellularly labelled neurons in cats and on 80 neurons labelled by retrograde transport of cholera toxin b subunit injected into the cerebellum of rats. In both species distribution of antibodies against VGLUT1 and VGLUT2 on SB neurons (which have dominating inhibitory input from limb muscles), revealed very few VGLUT1 contacts and remarkably high numbers of VGLUT2 contacts. In VSCT neurons with excitatory afferent input, the number of VGLUT1 contacts was relatively high although VGLUT2 contacts likewise dominated, while the proportions of VGLUT1 and VGLUT2 immunoreactive terminals were the reverse on the two populations of DSCT neurons. These findings provide morphological evidence that SB neurons principally receive excitatory inputs from central neurons and provide the cerebellum with information regarding central neuronal activity.
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Collateral Actions of Premotor Interneurons on Ventral Spinocerebellar Tract Neurons in the Cat
Journal of neurophysiology, 2010Co-Authors: Elzbieta Jankowska, Piotr Krutki, Ingela HammarAbstract:Strong evidence that premotor interneurons provide Ventral Spinocerebellar Tract (VSCT) neurons with feedback information on their actions on motoneurons was previously found for Ia inhibitory inte...
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Modulation of responses of feline Ventral Spinocerebellar Tract neurons by monoamines.
The Journal of comparative neurology, 2002Co-Authors: Ingela Hammar, Barbara Chojnicka, Elzbieta JankowskaAbstract:Ventral Spinocerebellar Tract neurons located in laminae V–VII of cat lumbar spinal cord were tested for the effects of ionophoretically applied monoamines and receptor selective agonists. Extracellularly recorded responses, monosynaptically evoked by group I afferents in a muscle nerve, were compared before, during, and after ionophoresis. They were analyzed with respect to changes in the number of evoked spikes and in the latency. Both serotonin (5-HT) and noradrenaline (NA) were found to facilitate responses of all neurons tested. Ionophoresis of three serotonin subtype receptor agonists (5-carboxamidotryptamine maleate, 5 methoxytryptamine HCl, and alpha-methyl 5-hydroxytryptamine) and of two NA receptor agonists (phenylephrine and isoproterenol) likewise had a facilitatory effect. However, three other 5-HT receptor agonists (8-hydroxy-dipropylaminotetraline hydrobromide), 2-methyl 5-hydroxytryptamine, and 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane HCl and two NA receptor agonists (tizanidine and clonidine) had the opposite effect because they depressed responses of the tested neurons. These results show that information forwarded by means of the Ventral Spinocerebellar Tract may be modulated by monoamines and that several receptor subtypes, located pre- or postsynaptically, may be involved. The results also demonstrate that transmission by means of group I muscle afferents may not only be facilitated by monoamines but also depressed by selective receptor subtype activation. J. Comp. Neurol. 443:298–309, 2002. © 2002 Wiley-Liss, Inc.
David J. Maxwell - One of the best experts on this subject based on the ideXlab platform.
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INHIBITORY INPUTS TO FOUR TYPES OF Spinocerebellar Tract NEURONS IN THE CAT SPINAL CORD
Neuroscience, 2012Co-Authors: S. Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:Spinocerebellar Tract neurons are inhibited by various sources of input via pathways activated by descending Tracts as well as peripheral afferents. Inhibition may be used to modulate transmission of excitatory information forwarded to the cerebellum. However it may also provide information on the degree of inhibition of motoneurons and on the operation of inhibitory premotor neurons. Our aim was to extend previous comparisons of morphological substrates of excitation of Spinocerebellar neurons to inhibitory input. Contacts formed by inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter, glutamic acid decarboxylase and gephyrin. Quantitative analysis revealed the presence of much higher proportions of inhibitory contacts when compared with excitatory contacts on spinal border (SB) neurons. However similar proportions of inhibitory and excitatory contacts were associated with Ventral Spinocerebellar Tract (VSCT) and dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and the dorsal horn (dhDSCT). In all of the cells, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal versus distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. Variations in the density and distribution of inhibitory contacts found in this study may reflect differences in information on inhibitory processes forwarded by subtypes of Spinocerebellar Tract neurons to the cerebellum.
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Excitatory inputs to four types of Spinocerebellar Tract neurons in the cat and the rat thoraco-lumbar spinal cord.
The Journal of physiology, 2012Co-Authors: Sony Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:The cerebellum receives information from the hindlimbs through several populations of Spinocerebellar Tract neurons. Although the role of these neurons has been established in electrophysiological experiments, the relative contribution of afferent fibres and central neurons to their excitatory input has only been estimated approximately so far. Taking advantage of differences in the immunohistochemistry of glutamatergic terminals of peripheral afferents and of central neurons (with vesicular glutamate transporters VGLUT1 or VGLUT2, respectively), we compared sources of excitatory input to four populations of Spinocerebellar neurons in the thoraco-lumbar spinal cord: dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and in the dorsal horn (dhDSCT) and Ventral Spinocerebellar Tract (VSCT) neurons including spinal border (SB) neurons. This was done on 22 electrophysiologically identified intracellularly labelled neurons in cats and on 80 neurons labelled by retrograde transport of cholera toxin b subunit injected into the cerebellum of rats. In both species distribution of antibodies against VGLUT1 and VGLUT2 on SB neurons (which have dominating inhibitory input from limb muscles), revealed very few VGLUT1 contacts and remarkably high numbers of VGLUT2 contacts. In VSCT neurons with excitatory afferent input, the number of VGLUT1 contacts was relatively high although VGLUT2 contacts likewise dominated, while the proportions of VGLUT1 and VGLUT2 immunoreactive terminals were the reverse on the two populations of DSCT neurons. These findings provide morphological evidence that SB neurons principally receive excitatory inputs from central neurons and provide the cerebellum with information regarding central neuronal activity.
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Serotoninergic and noradrenergic axons make contacts with neurons of the Ventral Spinocerebellar Tract in the cat
The Journal of comparative neurology, 2002Co-Authors: Ingela Hammar, David J. MaxwellAbstract:Contacts between monoaminergic fibers and electrophysiologically identified neurons of the Ventral Spinocerebellar Tract were investigated in the cat. Five neurons were labeled intracellularly with rhodamine dextran, and monoaminergic fibers were revealed with antibodies against serotonin and dopamine beta-hydroxylase. The distribution of appositions between monoaminergic varicosities and the soma and the whole length of dendrites of these neurons was examined by using a three-channel confocal microscope. The analysis showed that close appositions between monoaminergic fibers and labeled processes occurred over the whole surface of the neurons. The highest percentage of such appositions was found on proximal dendrites, for both serotonin (37%) and noradrenaline (57%). The total number of serotoninergic contacts (66–134 per neuron) by far exceeded that of noradrenergic contacts (3–36 per neuron). Contacts between serotoninergic fibers and two neurons were analyzed by using electron microscopy. These neurons were labeled intracellularly with horseradish peroxidase, and serotoninergic varicosities were identified by immunocytochemistry. Six of 10 serially analyzed boutons in apposition to proximal dendrites were found to form morphologic synapses. The identification of the remaining four was inconclusive. These results indicate that many of the appositions seen in confocal microscopy may represent direct synaptic contacts. They also indicate that monoaminergic neurons may modulate activity of neurons of the Ventral Spinocerebellar Tract by direct postsynaptic actions in addition to any effects evoked by means of volume transmission. J. Comp. Neurol. 443:310–319, 2002. © 2002 Wiley-Liss, Inc.
E. Nilsson - One of the best experts on this subject based on the ideXlab platform.
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A survey of spinal collateral actions of feline Ventral Spinocerebellar Tract neurons
The European journal of neuroscience, 2012Co-Authors: Pierre Geborek, E. Nilsson, Francesco Bolzoni, Elzbieta JankowskaAbstract:The aim of this study was to identify spinal target cells of Spinocerebellar neurons, in particular the Ventral Spinocerebellar Tract (VSCT) neurons, giving off axon collaterals terminating within the lumbosacral enlargement. Axons of Spinocerebellar neurons were stimulated within the cerebellum while searching for most direct synaptic actions on intracellularly recorded hindlimb motoneurons and interneurons. In motoneurons the dominating effects were inhibitory [inhibitory postsynaptic potentials (IPSPs) in 67% and excitatory postsynaptic potentials (EPSPs) in 17% of motoneurons]. Latencies of most IPSPs indicated that they were evoked disynaptically and mutual facilitation between these IPSPs and disynaptic IPSPs evoked by group Ia afferents from antagonist muscles and group Ib and II afferents from synergists indicated that they were relayed by premotor interneurons in reflex pathways from muscle afferents. Monosynaptic EPSPs from the cerebellum were accordingly found in Ia inhibitory interneurons and intermediate zone interneurons with input from group I and II afferents but only oligosynaptic EPSPs in motoneurons. Monosynaptic EPSPs following cerebellar stimulation were also found in some VSCT neurons, indicating coupling between various Spinocerebellar neurons. The results are in keeping with the previously demonstrated projections of VSCT neurons to the contralateral Ventral horn, showing that VSCT neurons might contribute to motor control at a spinal level. They might thus play a role in modulating spinal activity in advance of any control exerted via the cerebellar loop.
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INHIBITORY INPUTS TO FOUR TYPES OF Spinocerebellar Tract NEURONS IN THE CAT SPINAL CORD
Neuroscience, 2012Co-Authors: S. Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:Spinocerebellar Tract neurons are inhibited by various sources of input via pathways activated by descending Tracts as well as peripheral afferents. Inhibition may be used to modulate transmission of excitatory information forwarded to the cerebellum. However it may also provide information on the degree of inhibition of motoneurons and on the operation of inhibitory premotor neurons. Our aim was to extend previous comparisons of morphological substrates of excitation of Spinocerebellar neurons to inhibitory input. Contacts formed by inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter, glutamic acid decarboxylase and gephyrin. Quantitative analysis revealed the presence of much higher proportions of inhibitory contacts when compared with excitatory contacts on spinal border (SB) neurons. However similar proportions of inhibitory and excitatory contacts were associated with Ventral Spinocerebellar Tract (VSCT) and dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and the dorsal horn (dhDSCT). In all of the cells, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal versus distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. Variations in the density and distribution of inhibitory contacts found in this study may reflect differences in information on inhibitory processes forwarded by subtypes of Spinocerebellar Tract neurons to the cerebellum.
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Excitatory inputs to four types of Spinocerebellar Tract neurons in the cat and the rat thoraco-lumbar spinal cord.
The Journal of physiology, 2012Co-Authors: Sony Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:The cerebellum receives information from the hindlimbs through several populations of Spinocerebellar Tract neurons. Although the role of these neurons has been established in electrophysiological experiments, the relative contribution of afferent fibres and central neurons to their excitatory input has only been estimated approximately so far. Taking advantage of differences in the immunohistochemistry of glutamatergic terminals of peripheral afferents and of central neurons (with vesicular glutamate transporters VGLUT1 or VGLUT2, respectively), we compared sources of excitatory input to four populations of Spinocerebellar neurons in the thoraco-lumbar spinal cord: dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and in the dorsal horn (dhDSCT) and Ventral Spinocerebellar Tract (VSCT) neurons including spinal border (SB) neurons. This was done on 22 electrophysiologically identified intracellularly labelled neurons in cats and on 80 neurons labelled by retrograde transport of cholera toxin b subunit injected into the cerebellum of rats. In both species distribution of antibodies against VGLUT1 and VGLUT2 on SB neurons (which have dominating inhibitory input from limb muscles), revealed very few VGLUT1 contacts and remarkably high numbers of VGLUT2 contacts. In VSCT neurons with excitatory afferent input, the number of VGLUT1 contacts was relatively high although VGLUT2 contacts likewise dominated, while the proportions of VGLUT1 and VGLUT2 immunoreactive terminals were the reverse on the two populations of DSCT neurons. These findings provide morphological evidence that SB neurons principally receive excitatory inputs from central neurons and provide the cerebellum with information regarding central neuronal activity.
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Do Spinocerebellar neurones forward information on spinal actions of neurones in the feline red nucleus?
The Journal of physiology, 2011Co-Authors: E. Jankowska, E. Nilsson, I HammarAbstract:We recently demonstrated that feline Ventral Spinocerebellar Tract (VSCT) neurones monitor descending commands for voluntary movements initiated by pyramidal Tract (PT) neurones as well as locomotor movements relayed by reticulospinal (RS) neurones. The aim of the present study was to examine whether VSCT neurones likewise monitor descending commands from the red nucleus (RN). Extracellular records from the spinal border (SB) subpopulation of VSCT neurons revealed that a third (31%) of SB neurones may be discharged by trains of stimuli applied in the RN. Moreover, when RN stimuli failed to discharge SB neurones they facilitated activation of some of these neurones by RS and/or PT neurones, while activation of other SB neurones was depressed. We propose that the facilitation and depression of actions of RS neurones by RN neurones might serve to reflect a higher or lower excitability of motoneurones and therefore a likely higher or lower efficacy of the RS descending commands, prompting the cerebellum to adjust the activation of reticulospinal neurones. Activation of SB neurones by RN stimuli alone would also allow monitoring and adjusting the RN descending commands. Intracellular records from SB neurones revealed both monosynaptic and disynaptic EPSPs and disynaptic IPSPs evoked by RN stimuli. The disynaptic actions remained following transection of axons of reticulospinal neurones within the medullary longitudinal fascicle (MLF) and were therefore taken to be relayed primarily by spinal neurones, in contrast to EPSPs and IPSPs evoked by PT stimuli found to be relayed by reticulospinal rather than spinal neurones.
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Processing information related to centrally initiated locomotor and voluntary movements by feline Spinocerebellar neurones.
The Journal of physiology, 2011Co-Authors: E. Jankowska, E. Nilsson, I HammarAbstract:Feed-back information on centrally initiated movements is processed at both supraspinal and spinal levels and is forwarded by a variety of neurones. The aim of the present study was to examine how descending commands relayed by reticulospinal neurones are monitored by a population of Spinocerebellar Tract neurones. Our main question was whether a spinal border (SB) subpopulation of Ventral Spinocerebellar Tract (VSCT) neurones monitor actions of reticulospinal neurones with input from the mesencephalic locomotor region (MLR) as well as from pyramidal Tract (PT) neurones. In the majority of intracellularly recorded SB neurons, stimuli applied in the MLR and in the medullary pyramids evoked EPSPs in parallel with EPSPs evoked by stimulation of axons of reticulospinal neurones in the medial longitudinal fascicle (MLF). In extracellularly recorded neurones short trains of stimuli applied in the ipsilateral and contralateral pyramids potently facilitated discharges evoked from the MLF, as well as EPSPs recorded intracellularly. In both cases the facilitation involved the disynaptic but not the monosynaptic actions. These results indicate that reticulospinal neurones activating SB neurones (or more generally VSCT neurones) are co-excited by axon-collaterals of other reticulospinal neurones and by fibres stimulated within the MLR and PTs. The study leads to the conclusion that these Spinocerebellar neurones monitor descending commands for centrally initiated voluntary as well as locomotor movements relayed by reticulospinal neurones. Thereby they may provide the cerebellum with feed-back information on the likely outcome of these commands and any corrections needed to avoid errors in the issuing movements.
Sony Shakya Shrestha - One of the best experts on this subject based on the ideXlab platform.
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Excitatory inputs to four types of Spinocerebellar Tract neurons in the cat and the rat thoraco-lumbar spinal cord.
The Journal of physiology, 2012Co-Authors: Sony Shakya Shrestha, Elzbieta Jankowska, Ingela Hammar, B.a. Bannatyne, E. Nilsson, David J. MaxwellAbstract:The cerebellum receives information from the hindlimbs through several populations of Spinocerebellar Tract neurons. Although the role of these neurons has been established in electrophysiological experiments, the relative contribution of afferent fibres and central neurons to their excitatory input has only been estimated approximately so far. Taking advantage of differences in the immunohistochemistry of glutamatergic terminals of peripheral afferents and of central neurons (with vesicular glutamate transporters VGLUT1 or VGLUT2, respectively), we compared sources of excitatory input to four populations of Spinocerebellar neurons in the thoraco-lumbar spinal cord: dorsal Spinocerebellar Tract neurons located in Clarke's column (ccDSCT) and in the dorsal horn (dhDSCT) and Ventral Spinocerebellar Tract (VSCT) neurons including spinal border (SB) neurons. This was done on 22 electrophysiologically identified intracellularly labelled neurons in cats and on 80 neurons labelled by retrograde transport of cholera toxin b subunit injected into the cerebellum of rats. In both species distribution of antibodies against VGLUT1 and VGLUT2 on SB neurons (which have dominating inhibitory input from limb muscles), revealed very few VGLUT1 contacts and remarkably high numbers of VGLUT2 contacts. In VSCT neurons with excitatory afferent input, the number of VGLUT1 contacts was relatively high although VGLUT2 contacts likewise dominated, while the proportions of VGLUT1 and VGLUT2 immunoreactive terminals were the reverse on the two populations of DSCT neurons. These findings provide morphological evidence that SB neurons principally receive excitatory inputs from central neurons and provide the cerebellum with information regarding central neuronal activity.
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Input properties of four populations of Spinocerebellar Tract neurons in the cat and the rat thoraco-lumbar spinal cord
2012Co-Authors: Sony Shakya ShresthaAbstract:The cerebellum receives information from the hindlimbs through several populations of Spinocerebellar Tract neurons. Although the role of these neurons has been established in electrophysiological experiments, the relative contribution of afferent fibres and central neurons to their input, their organization and mechanisms of control of transmission has only been estimated approximately so far. The present study aimed to investigate the input properties of four populations of Spinocerebellar Tract neurons: dorsal Spinocerebellar Tract neurons located in Clarke´s column (ccDSCT) and in the dorsal horn (dhDSCT) and Ventral Spinocerebellar Tract (VSCT) neurons including spinal border (SB) neurons. There were three major aims: (1) to investigate the excitatory inputs to four types of Spinocerebellar Tract neurons in the cat and rat thoraco-lumbar spinal cord; (2) to analyze the inhibitory inputs to four types of Spinocerebellar Tract neurons in the cat and rat thoraco-lumbar spinal cord; (3) to determine the origin of excitatory and inhibitory inputs to four types of Spinocerebellar Tract neurons in the cat and rat thoraco-lumbar spinal cord. Two series of experiments were carried out. In the first series of experiments in cats, Spinocerebellar Tract neurons were identified electrophysiologically and labelled intracellularly with rhodamine-dextran and Neurobiotin. In the second series of experiments in rats, cells were labelled by retrograde transport of b-subunit of Cholera toxin (CTb) from the cerebellum. In addition, to address the third aim, reticulospinal (RetS) and corticospinal (CS) terminals were identified by anterograde transport of CTb from the caudal medulla and hindlimb sensory motor cortex respectively in rats along with labelling of Spinocerebellar Tract neurons by retrograde injection of Fluorogold in the cerebellum. Following this, immunohistochemistry was carried out. The first aim was achieved by utilizing the difference in the immunohistochemistry of glutamatergic terminals of peripheral afferents and of central neurons with vesicular glutamate transporters, VGLUT1 or VGLUT2, respectively. All SB neurons with dominating inhibitory input from the periphery possessed very few VGLUT1 contacts and remarkably higher numbers of VGLUT2 contacts. In VSCT neurons with excitatory primary afferent input, the number of VGLUT1 contacts was relatively high although VGLUT2 contacts likewise dominated. In contrast, DSCT neurons were associated with numerous VGLUT1 contacts; ccDSCT neurons with strong input from group I afferents had higher density of VGLUT1 contacts than dhDSCT neurons with major input from group II and cutaneous afferents. In order to fulfill the second aim, quantification of contacts formed by inhibitory axon terminals on Spinocerebellar Tract neurons along with excitatory terminals was carried out. Inhibitory axon terminals were characterised as either GABAergic, glycinergic or both GABAergic/glycinergic by using antibodies against vesicular GABA transporter (VGAT), glutamic acid decarboxylase (GAD) and gephyrin. Similarly, excitatory terminals were characterised by using combination of VGLUT1 and 2. The comparison revealed the presence of much higher proportions of inhibitory than excitatory contacts on SB neurons but similar proportions were found on VSCT, ccDSCT and dhDSCT neurons. In all types of cell, the majority of inhibitory terminals were glycinergic. The density of contacts was higher on somata and proximal in comparison with distal dendrites of SB and VSCT neurons but more evenly distributed in ccDSCT and dhDSCT neurons. To achieve the third aim, a series of immunohistochemical reactions was performed to characterize contacts that originate from proprioceptors, different types of interneurons and descending RetS and CS pathways. Among the four populations of Spinocerebellar Tract neurons, ccDSCT neurons had the highest proportion of contacts formed by VGLUT1 terminals double labeled with parvalbumin (PV) which indicated that majority of direct excitatory sensory inputs to ccDSCT neurons are derived from proprioceptors. A small proportion of excitatory and inhibitory contacts on these neurons originated from Calbindin/ Calretinin/ PV expressing neurons. Quantitative analysis revealed that SB and VSCT neurons have significantly higher numbers of appositions from VGLUT2 expressing RetS axon terminals than DSCT neurons. A small proportion of the RetS contacts on these neurons were VGAT positive. In contrast, DSCT neurons had higher numbers of appositions made by CS axon terminals in comparison to SB and VSCT neurons. The present findings provide a new basis for understanding the organization and functional connectivity of four populations of Spinocerebellar Tract neurons and strengthen previous indications of their functional differentiation. SB and VSCT neurons principally receive inputs from spinal and supraspinal neurons although direct input from primary afferents is also stronger in VSCT neurons. DSCT neurons have major direct input from primary afferents and also to some extent from the CS pathway but monosynaptic inputs from proprioceptors dominated in ccDSCT neurons and dhDSCT neurons have mixed proprioceptive and low threshold cutaneous afferent input.
