Evaluation of local synthesis of axonal proteins in the goldfish Mauthner cell axon and axons of dorsal and ventral roots of the rat in vitro

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.

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Characteristics of Slow Bursting Activities Recorded in Cervical Ventral Roots in the In Vitro Brainstem—Spinal Cord Preparation of the Neonatal Rat

Somatosensory & Motor Research ◽

10.3109/08990229409028857 ◽

1994 ◽

Vol 11 (1) ◽

pp. 57-64 ◽

Cited By ~ 7

Author(s):

L. Perségo ◽

D. Viala

Keyword(s):

Spinal Cord ◽

Neonatal Rat ◽

Ventral Roots

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

Journal of Neurophysiology ◽

10.1152/jn.1992.67.2.373 ◽

1992 ◽

Vol 67 (2) ◽

pp. 373-388 ◽

Cited By ~ 99

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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In Vivo Intracellular Analysis of Granule Cell Axon Reorganization in Epileptic Rats

Journal of Neurophysiology ◽

10.1152/jn.1999.81.2.712 ◽

1999 ◽

Vol 81 (2) ◽

pp. 712-721 ◽

Cited By ~ 119

Author(s):

Paul S. Buckmaster ◽

F. Edward Dudek

Keyword(s):

Granule Cell ◽

Granule Cells ◽

Molecular Layer ◽

Axon Collateral ◽

Cell Axon ◽

Recurrent Excitation ◽

The Difference ◽

Intracellular Analysis

In vivo intracellular analysis of granule cell axon reorganization in epileptic rats. In vivo intracellular recording and labeling in kainate-induced epileptic rats was used to address questions about granule cell axon reorganization in temporal lobe epilepsy. Individually labeled granule cells were reconstructed three dimensionally and in their entirety. Compared with controls, granule cells in epileptic rats had longer average axon length per cell; the difference was significant in all strata of the dentate gyrus including the hilus. In epileptic rats, at least one-third of the granule cells extended an aberrant axon collateral into the molecular layer. Axon projections into the molecular layer had an average summed length of 1 mm per cell and spanned 600 μm of the septotemporal axis of the hippocampus—a distance within the normal span of granule cell axon collaterals. These findings in vivo confirm results from previous in vitro studies. Surprisingly, 12% of the granule cells in epileptic rats, and none in controls, extended a basal dendrite into the hilus, providing another route for recurrent excitation. Consistent with recurrent excitation, many granule cells (56%) in epileptic rats displayed a long-latency depolarization superimposed on a normal inhibitory postsynaptic potential. These findings demonstrate changes, occurring at the single-cell level after an epileptogenic hippocampal injury, that could result in novel, local, recurrent circuits.

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Locomotor Rhythm Evoked by Ventrolateral Funiculus Stimulation in the Neonatal Rat Spinal Cord In Vitro

Journal of Neurophysiology ◽

10.1152/jn.1997.77.1.200 ◽

1997 ◽

Vol 77 (1) ◽

pp. 200-206 ◽

Cited By ~ 53

Author(s):

David S. K. Magnuson ◽

Tammy C. Trinder

Keyword(s):

Rhythmic Activity ◽

Ventral Root ◽

Neonatal Rat ◽

Rat Spinal Cord ◽

Locomotor Rhythm ◽

Ventral Roots ◽

Root Responses ◽

Bilateral Projection ◽

Ventrolateral Funiculus

Magnuson, David S. K. and Tammy C. Trinder. Locomotor rhythm evoked by ventrolateral funiculus stimulation in the neonatal rat spinal cord in vitro. J. Neurophysiol. 77: 200–206, 1997. Spinal cords from 2- to 8-day-old rats, maintained in vitro, were used to investigate the effects of discrete electrical stimuli applied to the ventrolateral funiculus (VLF) on motor neuron activity recorded from the lumbar ventral roots. Short trains of stimuli (1–3 s) delivered to one VLF in the low cervical region elicited rhythmic activity that persisted for up to 30 s. Responses consisted of short periods of activity (1–5 s) occurring simultaneously in the ipsilateral L5 and contralateral L3 ventral roots that alternated with similar bursts of activity in the ipsilateral L3 ventral root, a pattern consistent with locomotion. The rhythmicity of the ventral root responses to VLF stimulation was not affected by midsagittal sectioning of the preparation rostral to T10 and/or caudal to L4. Midsagittal sectioning of the lower thoracic or upper lumbar segments, however, disrupted the rhythmicity of the ventral root responses, leaving only long-duration simultaneous activation of the ipsilateral roots following VLF stimulus trains. The minimum lesion that effectively abolished the rhythmicity was one that divided only the L2 and L3 segments. In preparations rendered arrhythmic to VLF stimulation by an L2/L3 midsagittal lesion, rhythmicity could still be induced by N-methyl-d-aspartate (NMDA; 2–5 μM) and serotonin (5-HT; 20–50 μM), a drug combination commonly used to induce locomotor-like rhythmicity and air-stepping in vitro. Field potentials recorded following single stimuli delivered to the VLF revealed short-latency, large-amplitude responses in the ventral horn and intermediate gray both ipsilateral and contralateral to the stimulus site at T12 and L2. These observations suggest that 1) the discrete pathway under study may be an important descending locomotor command pathway and 2) this pathway has a strong bilateral projection in the lower thoracic and upper lumbar segments that is crucial for the initiation of VLF-induced rhythmic motor output. The induction of rhythmicity by NMDA/5-HT in an L2/L3-lesioned preparation suggests that these two rhythmogenic mechanisms may represent different levels within the circuitry that comprises the central pattern generator for locomotion. The rhythmic activity resulting from VLF stimulation is dependent on a bilateral projection that can be bypassed by the generalized excitation and subsequent rhythmicity that results from bath application of the NMDA/5-HT combination.

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