Organization of left–right coordination in the mammalian locomotor network

Butt, Simon J. B.; Lebret, James M.; Kiehn, Ole

doi:10.1016/s0165-0173(02)00194-7

Cited by 96 publications

(76 citation statements)

References 70 publications

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“…Electrophysiological recordings were performed from ventral roots (VRs) (Kiehn, 2006;Nistri et al, 2006) by means of suction electrodes; fictive locomotor patterns were obtained by recording the activity from left and right L2 VRs (mostly flexor motor-pool commands to the hindlimbs) and left and right L5 VRs (mostly extensor motor-pool commands to the hindlimbs) (Kiehn and Kjaerulff, 1998;Nistri et al, 2006). A typical indicator of fictive locomotion (Butt et al, 2002) is a pattern of discharge alternation between homosegmental left and right VRs and between L2/L5 VRs on the same side. All experiments were performed at RT.…”

Section: Methodsmentioning

confidence: 99%

ERG Conductance Expression Modulates the Excitability of Ventral Horn GABAergic Interneurons That Control Rhythmic Oscillations in the Developing Mouse Spinal Cord

Furlan¹,

Taccola²,

Grandolfo³

et al. 2007

J. Neurosci.

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During antenatal development, the operation and maturation of mammalian spinal networks strongly depend on the activity of ventral horn GABAergic interneurons that mediate excitation first and inhibition later. Although the functional consequence of GABA actions may depend on maturational processes in target neurons, it is also likely that evolving changes in GABAergic transmission require fine-tuning in GABA release, probably via certain intrinsic mechanisms regulating GABAergic neuron excitability at different embryonic stages. Nevertheless, it has not been possible, to date, to identify certain ionic conductances upregulated or downregulated before birth in such cells. By using an experimental model with either mouse organotypic spinal cultures or isolated spinal cord preparations, the present study examined the role of the ERG current (I K(ERG) ), a potassium conductance expressed by developing, GABA-immunoreactive spinal neurons. In organotypic cultures, only ventral interneurons with fast adaptation and GABA immunoreactivity, and only after 1 week in culture, were transformed into high-frequency bursters by E4031, a selective inhibitor of I K(ERG) that also prolonged and made more regular spontaneous bursts. In the isolated spinal cord in which GABA immunoreactivity and m-erg mRNA were colocalized in interneurons, ventral root rhythms evoked by NMDA plus 5-hydroxytryptamine were stabilized and synchronized by E4031. All of these effects were lost after 2 weeks in culture or before birth in coincidence with decreased m-erg expression. These data suggest that, during an early stage of spinal cord development, the excitability of GABAergic ventral interneurons important for circuit maturation depended, at least in part, on the function of I K(ERG) .

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Section: Methodsmentioning

confidence: 99%

ERG Conductance Expression Modulates the Excitability of Ventral Horn GABAergic Interneurons That Control Rhythmic Oscillations in the Developing Mouse Spinal Cord

Furlan¹,

Taccola²,

Grandolfo³

et al. 2007

J. Neurosci.

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“…For example, in locomotor circuits not every neuron is active with every movement (Butt et al, 2002).…”

Section: Intermittent Failures Of Optical and Electrical Signalsmentioning

confidence: 99%

Optical recording from respiratory pattern generator of fetal mouse brainstem reveals a distributed network

Eugenı́n¹,

Nicholls²,

Cohen³

et al. 2006

Neuroscience

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“…Although considerable data are now available on the neural substrates of bilateral limb coordination, particularly of lumbar spinal circuits controlling the hindlimbs of quadruped mammals (Kjaerulff and Kiehn, 1996;Rossignol, 1996;Kremer and LevTov, 1997;Cazalets and Bertrand, 2000;Butt et al, 2002), relatively little is known of the propriospinal processes that couple the forelimbs and hindlimbs (Viala and Vidal, 1978;English, 1979English, , 1989, which allow the switch between different modes of rostrocaudal coordination. Major problems in this respect include the identification of different neuronal pathways involved in coordinating and establishing their specific roles as well as deciphering the relationship between modes of coupling and the balance between processes of synaptic excitation and inhibition.…”

Section: Introductionmentioning

confidence: 99%

Propriospinal Circuitry Underlying Interlimb Coordination in Mammalian Quadrupedal Locomotion

Juvin¹,

Simmers²,

Morin³

2005

J. Neurosci.

197

174

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Soon after birth, freely moving quadrupeds can express locomotor activity with coordinated forelimb and hindlimb movements. To investigate the neural mechanisms underlying this coordination, we used an isolated spinal cord preparation from neonatal rats. Under bath-applied 5-HT, N-methyl-D,L-aspartate (NMA), and dopamine (DA), the isolated cord generates fictive locomotion in which homolateral cervicolumbar extensor motor bursts occur in phase opposition, as does bursting in homologous (left-right) extensor motoneurons. This coordination corresponded to a walking gait monitored with EMG recordings in the freely behaving animal. Functional decoupling of the cervical and lumbar generators in vitro by sucrose blockade at the thoracic cord level revealed independent rhythmogenic capabilities with similar cycle frequencies in the two locomotor regions. When the cord was partitioned at different thoracic levels and 5-HT/NMA/DA was applied to the more caudal compartment, the ability of the lumbar generators to drive their cervical counterparts increased with the proportion of chemically exposed thoracic segments. Blockade of synaptic inhibition at the lumbar level caused synchronous bilateral lumbar rhythmicity that, surprisingly, also was able to impose bilaterally synchronous bursting at the unblocked cervical level. Furthermore, after a midsagittal section from spinal segments C1 to T7, and during additional blockade of cervical synaptic inhibition, the cord exposed to 5-HT/NMA/DA continued to produce a coordinated fictive walking pattern similar to that observed in control. Thus, in the newborn rat, a caudorostral propriospinal excitability gradient appears to mediate interlimb coordination, which relies more on asymmetric axial connectivity (both excitatory and inhibitory) between the lumbar and cervical generators than on differences in their inherent rhythmogenic capacities.

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Organization of left–right coordination in the mammalian locomotor network

Cited by 96 publications

References 70 publications

ERG Conductance Expression Modulates the Excitability of Ventral Horn GABAergic Interneurons That Control Rhythmic Oscillations in the Developing Mouse Spinal Cord

ERG Conductance Expression Modulates the Excitability of Ventral Horn GABAergic Interneurons That Control Rhythmic Oscillations in the Developing Mouse Spinal Cord

Optical recording from respiratory pattern generator of fetal mouse brainstem reveals a distributed network

Propriospinal Circuitry Underlying Interlimb Coordination in Mammalian Quadrupedal Locomotion

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