Locomotor Pattern in the Adult Zebrafish Spinal Cord In Vitro

2008 ◽  
Vol 99 (1) ◽  
pp. 37-48 ◽  
Author(s):  
Jens Peter Gabriel ◽  
Riyadh Mahmood ◽  
Alexander M. Walter ◽  
Alexandros Kyriakatos ◽  
Giselbert Hauptmann ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Locomotor Activity ◽  
Rhythmic Activity ◽  
Adult Zebrafish ◽  
Whole Cell ◽  
Larval Stages ◽  
Cell Recording ◽  
Ventral Roots ◽  
Whole Cell Recordings

The zebrafish is an attractive model system for studying the function of the spinal locomotor network by combining electrophysiological, imaging, and genetic approaches. Thus far, most studies have been focusing on embryonic and larval stages. In this study we have developed an in vitro preparation of the isolated spinal cord from adult zebrafish in which locomotor activity can be induced while the activity of single neurons can be monitored using whole cell recording techniques. Application of NMDA elicited rhythmic locomotor activity that was monitored by recording from muscles or ventral roots in semi-intact or isolated spinal cord preparations, respectively. This rhythmic activity displayed a left–right alternation and a rostrocaudal delay. Blockade of glycinergic synaptic transmission by strychnine switched the alternating activity into synchronous bursting in the left and right sides as well as along the rostrocaudal axis. Whole cell recordings from motoneurons showed that they receive phasic synaptic inputs that were correlated with the locomotor activity recorded in ventral roots. This newly developed in vitro preparation of the adult zebrafish spinal cord will allow examination of the organization of the spinal locomotor network in an adult system to complement studies in zebrafish larvae and new born rodents.

Whole Cell Recordings of Lumbar Motoneurons During Locomotor-Like Activity in the In Vitro Neonatal Rat Spinal Cord

1998 ◽  
Vol 79 (2) ◽  
pp. 743-752 ◽  
Author(s):  
S. Hochman ◽  
B. J. Schmidt
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Rhythmic Activity ◽  
Input Resistance ◽  
Membrane Depolarization ◽  
Neonatal Rat ◽  
Rat Spinal Cord ◽  
Whole Cell ◽  
Whole Cell Recordings

Hochman, S. and B. J. Schmidt. Whole cell recordings of lumbar motoneurons during locomotor-like activity in the in vitro neonatal rat spinal cord. J. Neurophysiol. 79: 743–752, 1998. Whole cell current- and voltage-clamp recordings were obtained from lumbar motoneurons in the isolated neonatal rat spinal cord to characterize the behavior of motoneurons during neurochemically induced locomotor-like activity. Bath application of serotonin (10–100 μM) in combination with N-methyl-d-aspartate (1–12 μM) initially produced tonic membrane depolarization (mean = 26 mV), increased input resistance, decreased rheobase, and increased spike inactivation in response to depolarizing current pulse injections. After the initial tonic depolarization, rhythmic fluctuations of the motoneuron membrane potential (locomotor drive potentials; LDPs) developed that were modulated phasically in association with ventral root discharge. The peak and trough voltage levels of the LDP fluctuated above and below the membrane potential recorded immediately before the onset of rhythmic activity. Similarly, firing frequency was modulated above and below prelocomotion firing rates (in those motoneurons that displayed neurochemically induced tonic firing immediately before the onset of rhythmic activity). These observations are consistent with an alternation between phasic excitatory and inhibitory synaptic drives. The amplitude of LDPs and rhythmic excitatory drive current increased with membrane depolarization from −80 to −40 mV and then decreased with further depolarization, thus displaying nonlinear voltage-dependence. Faster frequency, small amplitude voltage fluctuations were observed superimposed on the depolarized phase of LDPs. In some motoneurons, the trajectory of these superimposed fluctuations was consistent with a synaptic origin, whereas in other cells, the regular sinusoidal appearance of the fluctuations and the occurrence of superimposed plateau potentials were more compatible with the activation of an intrinsic membrane property. One motoneuron displayed exclusively excitatory phasic drive, and another motoneuron was characterized by inhibitory phasic drive alone, during rhythmic activity. These findings are compatible with the concept of a central pattern generator that is capable of delivering both excitatory and inhibitory drive to motoneurons during locomotion. The data also suggest that the rhythmic excitatory and inhibitory outputs of the hypothetical half-center model can be dissociated and operate in isolation.

Whole Cell Recordings From Visualized Neurons in the Inner Laminae of the Functionally Intact Spinal Cord

2009 ◽  
Vol 102 (1) ◽  
pp. 590-597 ◽  
Author(s):  
Jason Dyck ◽  
Simon Gosgnach
Keyword(s):  
Neural Network ◽  
Spinal Cord ◽  
Locomotor Activity ◽  
Patch Clamp ◽  
Lumbar Spinal Cord ◽  
Whole Cell ◽  
Neuronal Populations ◽  
Cell Patch Clamp ◽  
Whole Cell Patch Clamp

The in vitro whole spinal cord preparation has been an invaluable tool for the study of the neural network that underlies walking because it provides a means of recording fictive locomotor activity following surgical and/or pharmacological manipulation. The recent use of molecular genetic techniques to identify discrete neuronal populations in the spinal cord and subsequent studies showing some of these populations to be involved in locomotor activity have been exciting developments that may lead to a better understanding of the structure and mechanism of function of this neural network. It would be of great benefit if the in vitro whole spinal cord preparation could be updated to allow for the direct targeting of genetically defined neuronal populations, allowing each to be characterized physiologically and anatomically. This report describes a new technique that enables the visualization of, and targeted whole cell patch-clamp recordings from, genetically defined populations of neurons while leaving connectivity largely intact. The key feature of this technique is a small notch cut in the lumbar spinal cord that reveals cells located in the intermediate laminae while leaving the ventral portion of the spinal cord—the region containing the locomotor neural network—untouched. Whole cell patch-clamp recordings demonstrate that these neurons are healthy and display large rhythmic depolarizations that are related to electroneurogram bursts recorded from ventral roots during fictive locomotion. Intracellular labeling demonstrates that this technique can also be used to map axonal projection patterns of neurons. We expect that this procedure will greatly facilitate electrophysiological and anatomical study of important neuronal populations that constitute neural networks throughout the CNS.

Mechanisms That Initiate Spontaneous Network Activity in the Developing Chick Spinal Cord

2001 ◽  
Vol 86 (3) ◽  
pp. 1481-1498 ◽  
Author(s):  
Peter Wenner ◽  
Michael J. O'Donovan
Keyword(s):  
Spinal Cord ◽  
Rhythmic Activity ◽  
Central Canal ◽  
Synaptic Activity ◽  
Network Activity ◽  
Whole Cell ◽  
Lateral Motor Column ◽  
Cell Recording ◽  
Random Fluctuations ◽  
Chick Spinal Cord

Many developing networks exhibit a transient period of spontaneous activity that is believed to be important developmentally. Here we investigate the initiation of spontaneous episodes of rhythmic activity in the embryonic chick spinal cord. These episodes recur regularly and are separated by quiescent intervals of many minutes. We examined the role of motoneurons and their intraspinal synaptic targets (R-interneurons) in the initiation of these episodes. During the latter part of the inter-episode interval, we recorded spontaneous, transient ventral root depolarizations that were accompanied by small, spatially diffuse fluorescent signals from interneurons retrogradely labeled with a calcium-sensitive dye. A transient often could be resolved at episode onset and was accompanied by an intense pre-episode (∼500 ms) motoneuronal discharge (particularly in adductor and sartorius) but not by interneuronal discharge monitored from the ventrolateral funiculus (VLF). An important role for this pre-episode motoneuron discharge was suggested by the finding that electrical stimulation of motor axons, sufficient to activate R-interneurons, could trigger episodes prematurely. This effect was mediated through activation of R-interneurons because it was prevented by pharmacological blockade of either the cholinergic motoneuronal inputs to R-interneurons or the GABAergic outputs from R-interneurons to other interneurons. Whole-cell recording from R-interneurons and imaging of calcium dye-labeled interneurons established that R-interneuron cell bodies were located dorsomedial to the lateral motor column (R-interneuron region). This region became active before other labeled interneurons when an episode was triggered by motor axon stimulation. At the beginning of a spontaneous episode, whole-cell recordings revealed that R-interneurons fired a high-frequency burst of spikes and optical recordings demonstrated that the R-interneuron region became active before other labeled interneurons. In the presence of cholinergic blockade, however, episode initiation slowed and the inter-episode interval lengthened. In addition, optical activity recorded from the R-interneuron region no longer led that of other labeled interneurons. Instead the initial activity occurred bilaterally in the region medial to the motor column and encompassing the central canal. These findings are consistent with the hypothesis that transient depolarizations and firing in motoneurons, originating from random fluctuations of interneuronal synaptic activity, activate R-interneurons, which then trigger the recruitment of the rest of the spinal interneuronal network. This unusual function for R-interneurons is likely to arise because the output of these interneurons is functionally excitatory during development.

scholarly journals Fictive Rhythmic Motor Patterns Induced by NMDA in an In Vitro Brain Stem–Spinal Cord Preparation From an Adult Urodele

1999 ◽  
Vol 82 (2) ◽  
pp. 1074-1077 ◽  
Author(s):  
Isabelle Delvolvé ◽  
Pascal Branchereau ◽  
Réjean Dubuc ◽  
Jean-Marie Cabelguen
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Rhythm Generation ◽  
Motor Patterns ◽  
Rhythmic Motor ◽  
Bath Application ◽  
The Neural Networks ◽  
Ventral Roots ◽  
Pleurodeles Waltl

An in vitro brain stem–spinal cord preparation from an adult urodele ( Pleurodeles waltl) was developed in which two fictive rhythmic motor patterns were evoked by bath application of N-methyl-d-aspartate (NMDA; 2.5–10 μM) with d-serine (10 μM). Both motor patterns displayed left-right alternation. The first pattern was characterized by cycle periods ranging between 2.4 and 9.0 s (4.9 ± 1.2 s, mean ± SD) and a rostrocaudal propagation of the activity in consecutive ventral roots. The second pattern displayed longer cycle periods (8.1–28.3 s; 14.2 ± 3.6 s) with a caudorostral propagation. The two patterns were inducible after a spinal transection at the first segment. Preliminary experiments on small pieces of spinal cord further suggested that the ability for rhythm generation is distributed along the spinal cord of this preparation. This study shows that the in vitro brain stem–spinal cord preparation from Pleurodeles waltl may be a useful model to study the mechanisms underlying the different axial motor patterns and the flexibility of the neural networks involved.

Neural mechanisms of intersegmental coordination in lamprey: local excitability changes modify the phase coupling along the spinal cord

1992 ◽  
Vol 67 (2) ◽  
pp. 373-388 ◽  
Author(s):  
T. Matsushima ◽  
S. Grillner
Keyword(s):  
Spinal Cord ◽  
Forward Direction ◽  
Neural Mechanisms ◽  
Cycle Duration ◽  
Phase Lag ◽  
High Concentration ◽  
Caudal Portion ◽  
Bath Application ◽  
Ventral Roots

1. To elucidate the neural mechanisms responsible for coordinating undulatory locomotor movements, the intersegmental phase lag was analyzed from ventral roots along the spinal cord during fictive swimming. It was induced by bath application of N-methyl-D-aspartate (NMDA) in in vitro preparations of lamprey spinal cord, while the excitability of different segments were modified. The phase lag between consecutive segments during normal forward swimming is 1% of the cycle duration in a broad range of values. Rostral segments are activated before more caudal ones. 2. Under control conditions, whole preparations (12-24 segment long; n = 22) were perfused with NMDA solutions of the same concentration (100-150 microM). The intersegmental phase lag values varied in a continuous range with a single peak around a median value of forward +0.74% per segment (range: forward +2.23% to backward -0.97%). 3. To examine whether excitability differences along the spinal cord could modify the intersegmental phase lag, different levels of excitatory amino acids (NMDA) were applied to spinal cord preparations positioned in a partitioned chamber. Different portions of the cord could be perfused separately by NMDA solutions of different concentrations (50-150 microM). If rostral segments were perfused with the higher NMDA solution, the lag was inevitably in the forward direction. Conversely, if the caudal portion was perfused with the higher NMDA solution, caudally located ventral roots became activated before the rostral ventral roots in a caudorostral succession, thus reversing the direction of the fictive swimming wave to propagate as during backward swimming. If the middle portion was perfused by the highest NMDA solution, this portion instead became leading, and the activity propagated from this point in both the rostral and the caudal directions. The portion located in the pool with highest NMDA concentration always gave rise to a "leading" segment. 4. When a portion of the preparation was perfused with an NMDA solution of a high concentration (75-150 microM), the cycle duration was close to that recorded when the whole preparation was perfused with the same high NMDA solution. The ensemble cycle duration is, therefore, largely determined by the leading segment. 5. The phase lag changes were not restricted to the region around the barrier separating pools with different NMDA solutions.(ABSTRACT TRUNCATED AT 400 WORDS)

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