Evidence for a Widespread Brain Stem Escape Network in Larval Zebrafish

2002 ◽  
Vol 87 (1) ◽  
pp. 608-614 ◽  
Author(s):  
Ethan Gahtan ◽  
Nagarajan Sankrithi ◽  
Jeanette B. Campos ◽  
Donald M. O'Malley
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Neural Control ◽  
Escape Behavior ◽  
Confocal Imaging ◽  
Medial Longitudinal Fasciculus ◽  
Mauthner Cell ◽  
Larval Zebrafish ◽  
Descending Neurons

Zebrafish escape behaviors, which typically consist of a C bend, a counter-turn, and a bout of rapid swimming, are initiated by firing of the Mauthner cell and two segmental homologs. However, after laser-ablation of the Mauthner cell and its homologs, escape-like behaviors still occur, albeit at a much longer latency. This might suggest that additional neurons contribute to this behavior. We therefore recorded the activity of other descending neurons in the brain stem using confocal imaging of cells retrogradely labeled with fluorescent calcium indicators. A large majority of identified descending neurons present in the larval zebrafish, including both ipsilaterally and contralaterally projecting reticulospinal neurons, as well as neurons from the nucleus of the medial longitudinal fasciculus, showed short-latency calcium responses after gentle taps to the head of the larva—a stimulus that reliably evokes an escape behavior. Previous studies had associated such in vivo calcium responses with the firing of action potentials, and because all responding cells have axons projecting into to spinal cord, this suggests that these cells are relaying escape-related information to spinal cord. Other identified neurons failed to show consistent calcium responses to escape-eliciting stimuli. In conjunction with previous lesion studies, these results indicate that the neural control systems for turning and swimming behaviors are widely distributed in the larval zebrafish brain stem. The degree of robustness or redundancy of this system has implications for the descending control of vertebrate locomotion.

scholarly journals Individual neuronal subtypes control initial myelin sheath growth and stabilization

2020 ◽  
Vol 15 (1) ◽  
Author(s):  
Heather N. Nelson ◽  
Anthony J. Treichel ◽  
Erin N. Eggum ◽  
Madeline R. Martell ◽  
Amanda J. Kaiser ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Myelin Sheath ◽  
Time Lapse ◽  
Marked Individual ◽  
Larval Zebrafish ◽  
Sheath Formation ◽  
Time Lapse Imaging

Abstract Background In the developing central nervous system, pre-myelinating oligodendrocytes sample candidate nerve axons by extending and retracting process extensions. Some contacts stabilize, leading to the initiation of axon wrapping, nascent myelin sheath formation, concentric wrapping and sheath elongation, and sheath stabilization or pruning by oligodendrocytes. Although axonal signals influence the overall process of myelination, the precise oligodendrocyte behaviors that require signaling from axons are not completely understood. In this study, we investigated whether oligodendrocyte behaviors during the early events of myelination are mediated by an oligodendrocyte-intrinsic myelination program or are over-ridden by axonal factors. Methods To address this, we utilized in vivo time-lapse imaging in embryonic and larval zebrafish spinal cord during the initial hours and days of axon wrapping and myelination. Transgenic reporter lines marked individual axon subtypes or oligodendrocyte membranes. Results In the larval zebrafish spinal cord, individual axon subtypes supported distinct nascent sheath growth rates and stabilization frequencies. Oligodendrocytes ensheathed individual axon subtypes at different rates during a two-day period after initial axon wrapping. When descending reticulospinal axons were ablated, local spinal axons supported a constant ensheathment rate despite the increased ratio of oligodendrocytes to target axons. Conclusion We conclude that properties of individual axon subtypes instruct oligodendrocyte behaviors during initial stages of myelination by differentially controlling nascent sheath growth and stabilization.

In vivo Brillouin microscopy of the larval zebrafish spinal cord (Conference Presentation)

2018 ◽  
Author(s):  
Raimund Schlüßler ◽  
Stephanie Möllmert ◽  
Jürgen Czarske ◽  
Jochen Guck
Keyword(s):  
Spinal Cord ◽  
Larval Zebrafish

Excitation of lumbar motoneurons by the medial longitudinal fasciculus in the in vitro brain stem spinal cord preparation of the neonatal rat

1993 ◽  
Vol 70 (6) ◽  
pp. 2241-2250 ◽  
Author(s):  
M. K. Floeter ◽  
A. Lev-Tov
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Short Latency ◽  
Medial Longitudinal Fasciculus ◽  
Paired Pulse ◽  
Long Latency ◽  
The Brain ◽  
Pulse Stimulation ◽  
Stimulation Of

1. The excitation of lumbar motoneurons by reticulospinal axons traveling in the medial longitudinal fasciculus (MLF) was investigated in the newborn rat using intracellular recordings from lumbar motoneurons in an in vitro preparation of the brain stem and spinal cord. The tracer DiI (1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine) was introduced into the MLF of 6-day-old littermate rats that had been fixed with paraformaldehyde to evaluate the anatomic extent of this developing pathway. 2. Fibers labeled from the MLF by DiI were present in the cervical ventral and lateral white matter and a smaller number of labeled fibers extended to the lumbar enlargement. Patches of sparse terminal labeling were seen in the lumbar ventral gray. 3. In the in vitro preparation of the brain stem and spinal cord, MLF stimulation excited motoneurons through long-latency pathways in most motoneurons and through both short-(< 40 ms) and long-latency connections in 16 of 40 motoneurons studied. Short- and longer-latency components of the excitatory response were evaluated using mephenesin to reduce activity in polysynaptic pathways. 4. Paired-pulse stimulation of the MLF revealed a modest temporal facilitation of the short-latency excitatory postsynaptic potential (EPSP) at short interstimulus intervals (20–200 ms). Trains of stimulation at longer interstimulus intervals (1–30 s) resulted in a depression of EPSP amplitude. The time course of the synaptic depression was compared with that found in EPSPs resulting from paired-pulse stimulation of the dorsal root and found to be comparable. 5. The short-latency MLF EPSP was reversibly blocked by 6-cyano-7-nitroquinoxaline (CNQX), an antagonist of non-N-methyl-D-aspartate glutamate receptors, with a small CNQX-resistant component. Longer-latency components of the MLF EPSP were also blocked by CNQX, and some late components of the PSP were sensitive to strychnine. MLF activation of multiple polysynaptic pathways in the spinal cord is discussed.

Short-term desensitization of fast escape behavior associated with suppression of Mauthner cell activity in larval zebrafish

2017 ◽  
Vol 121 ◽  
pp. 29-36 ◽  
Author(s):  
Megumi Takahashi ◽  
Maya Inoue ◽  
Masashi Tanimoto ◽  
Tsunehiko Kohashi ◽  
Yoichi Oda
Keyword(s):  
Escape Behavior ◽  
Cell Activity ◽  
Short Term ◽  
Mauthner Cell ◽  
Larval Zebrafish

scholarly journals Synthesis, transport, and metabolism of serotonin formed from exogenously applied 5-HTP after spinal cord injury in rats

2014 ◽  
Vol 111 (1) ◽  
pp. 145-163 ◽  
Author(s):  
Yaqing Li ◽  
Lisa Li ◽  
Marilee J. Stephens ◽  
Dwight Zenner ◽  
Katherine C. Murray ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Injury ◽  
Brain Stem ◽  
Tryptophan Hydroxylase ◽  
Acid Decarboxylase ◽  
Amino Acid Decarboxylase ◽  
Cord Injury ◽  
Motoneuron Activity

Spinal cord transection leads to elimination of brain stem-derived monoamine fibers that normally synthesize most of the monoamines in the spinal cord, including serotonin (5-hydroxytryptamine, 5-HT) synthesized from tryptophan by enzymes tryptophan hydroxylase (TPH, synthesizing 5-hydroxytryptophan, 5-HTP) and aromatic l-amino acid decarboxylase (AADC, synthesizing 5-HT from 5-HTP). Here we examine whether spinal cord caudal to transection remains able to manufacture and metabolize 5-HT. Immunolabeling for AADC reveals that, while most AADC is confined to brain stem-derived monoamine fibers in spinal cords from normal rats, caudal to transection AADC is primarily found in blood vessel endothelial cells and pericytes as well as a novel group of neurons (NeuN positive and GFAP negative), all of which strongly upregulate AADC with injury. However, immunolabeling for 5-HT reveals that there is no detectable endogenous 5-HT synthesis in any structure in the spinal cord caudal to a chronic transection, including in AADC-containing vessels and neurons, consistent with a lack of TPH. In contrast, when we applied exogenous 5-HTP (in vitro or in vivo), AADC-containing vessels and neurons synthesized 5-HT, which contributed to increased motoneuron activity and muscle spasms (long-lasting reflexes, LLRs), by acting on 5-HT2receptors (SB206553 sensitive) located on motoneurons (TTX resistant). Blocking monoamine oxidase (MAO) markedly increased the sensitivity of the motoneurons (LLR) to 5-HTP, more than it increased the sensitivity of motoneurons to 5-HT, suggesting that 5-HT synthesized from AADC is largely metabolized in AADC-containing neurons and vessels. In summary, after spinal cord injury AADC is upregulated in vessels, pericytes, and neurons but does not endogenously produce 5-HT, whereas when exogenous 5-HTP is provided AADC does produce functional amounts of 5-HT, some of which is able to escape metabolism by MAO, diffuse out of these AADC-containing cells, and ultimately act on 5-HT receptors on motoneurons.

scholarly journals Spinal V2b neurons reveal a role for ipsilateral inhibition in speed control

eLife ◽  
2019 ◽  
Vol 8 ◽  
Author(s):  
Rebecca A Callahan ◽  
Richard Roberts ◽  
Mohini Sengupta ◽  
Yukiko Kimura ◽  
Shin-ichi Higashijima ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Motor Neurons ◽  
Speed Control ◽  
Morphological Properties ◽  
Larval Zebrafish ◽  
Motor Circuits ◽  
Transgenic Lines ◽  
Left And Right

The spinal cord contains a diverse array of interneurons that govern motor output. Traditionally, models of spinal circuits have emphasized the role of inhibition in enforcing reciprocal alternation between left and right sides or flexors and extensors. However, recent work has shown that inhibition also increases coincident with excitation during contraction. Here, using larval zebrafish, we investigate the V2b (Gata3+) class of neurons, which contribute to flexor-extensor alternation but are otherwise poorly understood. Using newly generated transgenic lines we define two stable subclasses with distinct neurotransmitter and morphological properties. These V2b subclasses synapse directly onto motor neurons with differential targeting to speed-specific circuits. In vivo, optogenetic manipulation of V2b activity modulates locomotor frequency: suppressing V2b neurons elicits faster locomotion, whereas activating V2b neurons slows locomotion. We conclude that V2b neurons serve as a brake on axial motor circuits. Together, these results indicate a role for ipsilateral inhibition in speed control.

Neural mechanisms generating respiratory pattern in mammalian brain stem-spinal cord in vitro. I. Spatiotemporal patterns of motor and medullary neuron activity

1990 ◽  
Vol 64 (4) ◽  
pp. 1149-1169 ◽  
Author(s):  
J. C. Smith ◽  
J. J. Greer ◽  
G. S. Liu ◽  
J. L. Feldman
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
High Frequency ◽  
Neonatal Rat ◽  
Amplitude Fluctuations ◽  
Frequency Components ◽  
Afferent Inputs ◽  
Synaptic Drive

1. An analysis of the spatial and temporal patterns of activity of neurons of the respiratory motor-pattern generation system in an in vitro neonatal rat brain stem-spinal cord preparation is presented. Impulse discharge patterns of spinal and cranial moto-neurons as well as respiratory neurons in the medulla were analyzed. Patterns of motoneuronal discharge were characterized at the population level from recordings of motor-nerve discharge and at the single-cell level from intracellular recordings. These patterns were compared to patterns generated in the neonatal rat and adult mammal in vivo to establish the correspondence between in vitro and in vivo states. 2. The in vitro system generated a complex spatiotemporal pattern of spinal and cranial motoneuron activity during inspiratory (I) and expiratory (E) phases of the respiratory cycle. The respiratory cycle consisted of three distinct phases of neuronal activity (I, early E, and late E phase) similar to the temporal organization of the cycle in the intact mammal. The spike discharge pattern of motoneurons during the I phase consisted of a rapidly peaking-slowly decrementing discharge envelope with a high degree of synchronization on a time scale of 25-50 ms (approximately 20-40 Hz). A similar pattern was generated in the neonate in vivo under conditions comparable with the in vitro state (i.e., nervous system isolated from mechanosensory afferent inputs). However, the I-phase-motoneuron discharge pattern and cycle-phase durations differed from those characteristic of the intact neonatal or adult systems in vivo. This difference could be accounted for primarily by removal of vagal mechanosensory afferent inputs. 3. The synaptic drive potentials of spinal motoneurons during the I phase in vitro consisted of a rapidly peaking-slowly decrementing potential envelope similar in shape to the spike-frequency histogram of single motoneurons and the envelope of the motoneuron-population discharge. The drive potentials had prominent high-frequency amplitude fluctuations superimposed on the slower drive-potential envelope that were temporally correlated with the generation of motoneuron action potentials. The dominant frequency components of these fast-membrane-potential oscillations (20-35 Hz) were similar to the frequency components of the amplitude fluctuations in the motoneuron-population discharge. One class of medullary neurons with I-phase discharge also exhibited a rapidly peaking-slowly decrementing pattern of impulse discharge and synaptic drive potential with similar high-frequency components.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals In Vivo Imaging of Functional Inhibitory Networks on the Mauthner Cell of Larval Zebrafish

2002 ◽  
Vol 22 (10) ◽  
pp. 3929-3938 ◽  
Author(s):  
Masaharu Takahashi ◽  
Madoka Narushima ◽  
Yoichi Oda
Keyword(s):  
In Vivo Imaging ◽  
Mauthner Cell ◽  
Larval Zebrafish ◽  
Inhibitory Networks

scholarly journals Individual neuronal subtypes control initial myelin sheath growth and stabilization

2019 ◽  
Author(s):  
Heather N. Nelson ◽  
Anthony J. Treichel ◽  
Erin N. Eggum ◽  
Madeline R. Martell ◽  
Amanda J. Kaiser ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Central Nervous System ◽  
Nervous System ◽  
Myelin Sheath ◽  
Time Lapse ◽  
Marked Individual ◽  
Larval Zebrafish ◽  
Sheath Formation ◽  
Time Lapse Imaging

AbstractBackgroundIn the developing central nervous system, pre-myelinating oligodendrocytes sample candidate nerve axons by extending and retracting process extensions. Some contacts stabilize, leading to the initiation of axon wrapping, nascent myelin sheath formation, concentric wrapping and sheath elongation, and sheath stabilization or pruning by oligodendrocytes. Although axonal signals influence the overall process of myelination, the precise oligodendrocyte behaviors that require signaling from axons are not completely understood. In this study, we investigated whether oligodendrocyte behaviors during the early events of myelination are mediated by an oligodendrocyte-intrinsic myelination program or are over-ridden by axonal factors.MethodsTo address this, we utilized in vivo time-lapse imaging in embryonic and larval zebrafish spinal cord during the initial hours and days of axon wrapping and myelination. Transgenic reporter lines marked individual axon subtypes or oligodendrocyte membranes.ResultsIn the larval zebrafish spinal cord, individual axon subtypes supported distinct nascent sheath growth rates and stabilization frequencies. Oligodendrocytes ensheathed individual axon subtypes at different rates during a two-day period after initial axon wrapping. When descending reticulospinal axons were ablated, local spinal axons supported a constant ensheathment rate despite the increased ratio of oligodendrocytes to target axons.ConclusionWe conclude that properties of individual axon subtypes instruct oligodendrocyte behaviors during initial stages of myelination by differentially controlling nascent sheath growth and stabilization.

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