scholarly journals Synergistic integration of Netrin and ephrin axon guidance signals by spinal motor neurons

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Sebastian Poliak ◽  
Daniel Morales ◽  
Louis-Philippe Croteau ◽  
Dayana Krawchuk ◽  
Elena Palmesino ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Molecular Mechanisms ◽  
Neural Circuit ◽  
Growth Cones ◽  
In Vitro Assays ◽  
Dependent Manner ◽  
Motor Axons ◽  
Spinal Motor Neurons ◽  
Spinal Motor

During neural circuit assembly, axonal growth cones are exposed to multiple guidance signals at trajectory choice points. While axonal responses to individual guidance cues have been extensively studied, less is known about responses to combination of signals and underlying molecular mechanisms. Here, we studied the convergence of signals directing trajectory selection of spinal motor axons entering the limb. We first demonstrate that Netrin-1 attracts and repels distinct motor axon populations, according to their expression of Netrin receptors. Quantitative in vitro assays demonstrate that motor axons synergistically integrate both attractive or repulsive Netrin-1 signals together with repulsive ephrin signals. Our investigations of the mechanism of ephrin-B2 and Netrin-1 integration demonstrate that the Netrin receptor Unc5c and the ephrin receptor EphB2 can form a complex in a ligand-dependent manner and that Netrin–ephrin synergistic growth cones responses involve the potentiation of Src family kinase signaling, a common effector of both pathways.

Inhibition of motor axon growth by T-cadherin substrata

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 3163-3171 ◽  
Author(s):  
B.J. Fredette ◽  
J. Miller ◽  
B. Ranscht
Keyword(s):  
Motor Neurons ◽  
Axon Growth ◽  
Neurite Growth ◽  
Motor Axon ◽  
Spinal Motor Neurons ◽  
Guidance Cue ◽  
Spinal Motor ◽  
Neuron Populations ◽  
Muscle Innervation

As spinal motor neurons project to their hindlimb targets, their growth cones avoid particular regions along their pathway. T-cadherin is discretely distributed in the avoided caudal sclerotome and on extrasynaptic muscle surfaces (B. J. Fredette and B. Ranscht (1994) J. Neurosci. 14, 7331–7346), and therefore, the ability of T-cadherin to inhibit neurite growth was tested in vitro. T-cadherin inhibited neurite extension from select neuron populations both as a substratum, and as a soluble recombinant protein. Anti-T-cadherin antibodies neutralized the inhibition. Spinal motor neurons were inhibited only during the stages of axon growth across the sclerotome and muscle innervation. Inhibitory responses corresponded to neuronal T-cadherin expression, suggesting a homophilic binding mechanism. These results suggest that T-cadherin is a negative guidance cue for motor axon projections.

Volatile Anesthetics Depress Spinal Motor Neurons

1996 ◽  
Vol 85 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Ira J. Rampil ◽  
Bryan S. King
Keyword(s):  
Motor Neurons ◽  
Muscle Activation ◽  
Wave Amplitude ◽  
Dependent Manner ◽  
Noninvasive Technique ◽  
Inhaled Anesthetics ◽  
Spinal Motor Neurons ◽  
Spinal Motor ◽  
Motor Neuron Excitability ◽  
F Wave

Background Depression of spinal alpha-motor neurons apparently plays a role in the surgical immobility induced by isoflurane. Using the noninvasive technique of F-wave analysis, the authors tested the hypothesis that depressed motor neuron excitability is an effect common to other clinically relevant inhaled anesthetics. Methods The authors measured F-wave amplitude in rats anesthetized with desflurane, enflurane, halothane, or sevoflurane. Each animal received one anesthetic at five equipotent anesthetic concentrations (0.6, 0.8, 1.2, and 1.6 minimum alveolar concentration [MAC] and 0.8 MAC with 65% N2O). F waves were detected as late potentials in electromyographic responses evoked in the intrinsic muscles of the hind paw after monopolar stimulation of the ipsilateral posterior tibial nerve. Results All tested inhaled anesthetics depressed F-wave amplitude but not M-wave (orthodromic, early muscle activation) amplitude, and increased M-F latency in a dose-dependent manner. At 1.0 MAC, the estimated F/M ratio was 70 +/- 13% SD of that at baseline (0.6 MAC). Nitrous oxide added to 0.8 MAC of the potent vapors depressed F/M ratio by 63 +/- 17%. Conclusions All anesthetics tested appeared to depress the excitability of spinal motor neurons. This effect may contribute to surgical immobility, and its magnitude is comparable at equipotent concentrations of agents. The authors hypothesize that this effect is due to hyperpolarization, although, currently, there is insufficient information to discriminate between pre- and postsynaptic mechanisms.

scholarly journals A Brainstem reticulotegmental neural ensemble drives acoustic startle reflexes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Weiwei Guo ◽  
Sijia Fan ◽  
Dan Xiao ◽  
Hui Dong ◽  
Guangwei Xu ◽  
...  
Keyword(s):  
Motor Neurons ◽  
Neural Circuit ◽  
Acoustic Startle ◽  
Auditory Information ◽  
Spinal Motor Neurons ◽  
Glutamatergic Neurons ◽  
Spinal Motor ◽  
Neural Ensemble ◽  
Crucial Component

AbstractThe reticulotegmental nucleus (RtTg) has long been recognized as a crucial component of brainstem reticular formation (RF). However, the function of RtTg and its related circuits remain elusive. Here, we report a role of the RtTg in startle reflex, a highly conserved innate defensive behaviour. Optogenetic activation of RtTg neurons evokes robust startle responses in mice. The glutamatergic neurons in the RtTg are significantly activated during acoustic startle reflexes (ASR). Chemogenetic inhibition of the RtTg glutamatergic neurons decreases the ASR amplitudes. Viral tracing reveals an ASR neural circuit that the cochlear nucleus carrying auditory information sends direct excitatory innervations to the RtTg glutamatergic neurons, which in turn project to spinal motor neurons. Together, our findings describe a functional role of RtTg and its related neural circuit in startle reflexes, and demonstrate how the RF connects auditory system with motor functions.

scholarly journals Can Hybrid Synapse be Formed between Rat Spinal Motor Neurons and Major Pelvic Ganglion Neurons in vitro?

2021 ◽  
Vol 26 (6) ◽  
pp. 521-526
Author(s):  
Shigang CHENG ◽  
Xuan XIANG ◽  
Zemin LV ◽  
Xiaowen MAO ◽  
Xinghai YANG
Keyword(s):  
Motor Neurons ◽  
Synapse Formation ◽  
Fluorescent Protein ◽  
Pelvic Ganglion ◽  
Spinal Motor Neurons ◽  
Spinal Motor ◽  
Major Pelvic Ganglion ◽  
Reflex Arc ◽  
Ganglion Neurons

The purpose of this study is to determine whether synapses can be formed between spinal motor neurons (SMNs) and major pelvic ganglion (MPG) neurons of a rat in vitro. The green fluorescent protein (GFP)-labelled MPG cells were cultured together with SMNs in a specific medium. The synaptic-like contacts established between SMNs and MPG neurons were studied in co-cultures using morphologic and immunocytochemistry approaches. Phase-contrast observation of co-cultures showed apparent SMNs-MPG neurons contacts as early as three or four days in vitro. We demonstrate some evidence of synaptic contacts between SMNs and MPG neurons in vitro by immunostaining with antibody directed against postsynaptic density protein 95 (PSD-95). We describe the development process of a defined SMNs-MPG neurons co-culture system. The results suggest that the hybrid synapse formation that may occur between SMNs and MPG neurons in vitro played an essential role in the mechanisms of a regenerated bladder with an artificial somatic-autonomic reflex arc.

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