Developmental Reorganization of the Output of a GABAergic Interneuronal Circuit

2007 ◽  
Vol 97 (4) ◽  
pp. 2769-2779 ◽  
Author(s):  
Huaying Xu ◽  
Arthur Clement ◽  
Terrence Michael Wright ◽  
Peter Wenner
Keyword(s):  
Spinal Cord ◽  
Chick Embryo ◽  
Synaptic Input ◽  
Ventral Root ◽  
Network Activity ◽  
Inhibitory Interneurons ◽  
Optical Studies ◽  
Adjacent Segments ◽  
Whole Cell Recordings ◽  
Stimulation Of

Locally projecting inhibitory interneurons play a crucial role in the patterning and timing of network activity. However, because of their relative inaccessibility, little is known about their development or incorporation into circuits. In this report we demonstrate that the GABAergic R-interneuron circuit undergoes a reorganization in the chick embryo spinal cord between embryonic days 8 and 15 (E8 and E15). R-interneurons receive synaptic input from and project back to motoneurons. By stimulating motoneurons projecting in one ventral root and recording the disynaptic response from motoneurons in adjacent segments, we show that the output of the R-interneuron circuit is reorganized during development. After stimulation of the LS2 ventral root, disynaptic responses observed in whole cell recordings became more common and stronger for LS3 motoneurons and less common for the more distant LS4 motoneurons from E8 to E10. Optical studies demonstrated that R-interneurons activated by LS2 stimulation were restricted to the LS2 segment and had a small glutamatergic component at both E8 and E10, but that more R-interneurons were activated within the segment by E10. The recruitment of more LS2 R-interneurons at E10 is likely to contribute to stronger projections to LS3 motoneurons, but the fact that fewer LS4 motoneurons receive this input is more consistent with a functional refinement of the more distant projection of the GABAergic R-interneuron. Interestingly, this pattern of reorganization was not observed throughout the rostrocaudal extent of the cord, introducing the possibility that refinement could serve to remove connections between functionally unrelated interneurons and motoneurons.

Tonic and phasic synaptic input to spinal cord motoneurons during fictive locomotion in frog embryos

1982 ◽  
Vol 48 (6) ◽  
pp. 1279-1288 ◽  
Author(s):  
S. R. Soffe ◽  
A. Roberts
Keyword(s):  
Spinal Cord ◽  
Synaptic Input ◽  
Inhibitory Interneurons ◽  
Fictive Locomotion ◽  
Inhibitory Pathway ◽  
Intact Side ◽  
Rhythmic Motor ◽  
Postsynaptic Potential ◽  
Late Developmental Stage ◽  
Motor Root

1. In curarized, late developmental stage Xenopus embryos, episodes of rhythmic motor root discharge, termed fictive swimming (17), may be evoked by touch or by dimming the lights, as in unparalyzed animals. Motoneurons are tonically depolarized throughout each episode, are phasically excited to fire 1 spike per cycle, and receive a midcycle inhibitory postsynaptic potential (IPSP) in phase with motor root activity on the opposite side. 2. Rostral hemisection of the spinal cord abolishes motor root discharge on the operated side caudal to the cut but leaves activity on the intact side unaffected. In motoneurons, the tonic depolarization is abolished on the hemisected side but is still present on the intact side. This is evidence that the tonic depolarization is a descending drive. 3. Midcycle IPSPs normally seen in motoneurons during fictive swimming are abolished by rostral hemisection of the opposite side of the cord but are still recorded on the cut side. The simplest conclusion is that the inhibitory interneurons responsible lie on the opposite side of the spinal cord to the motoneurons they inhibit, and so represent a reciprocal inhibitory pathway. 4. The phasic excitatory postsynaptic potentials (EPSPs), which drive motoneuron spikes during swimming, are still present on the intact side of a rostrally hemisected cord but are abolished on the operated side. We conclude that the excitatory interneurons responsible lie on the same side of the cord as the motoneurons they excite.

Use of NK1 receptor antagonists in the exploration of physiological functions of substance P and neurokinin A

1995 ◽  
Vol 73 (7) ◽  
pp. 903-907 ◽  
Author(s):  
M. Qtsuka ◽  
K. Yoshioka ◽  
M. Yanagisawa ◽  
H. Suzuki ◽  
F.-Y. Zhao ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Substance P ◽  
Guinea Pig ◽  
Saphenous Nerve ◽  
Ventral Root ◽  
Neonatal Rat ◽  
Neurokinin A ◽  
Receptor Antagonists ◽  
Stimulation Of

Tachykinin NK1 receptor antagonists were used to explore the physiological functions of substance P (SP) and neurokinin A (NKA). Pharmacological profiles of three NK1 receptor antagonists, GR71251, GR82334, and RP 67580, were examined in the isolated spinal cord preparation of the neonatal rat. These tachykinin receptor antagonists exhibited considerable specificities and antagonized the actions of both SP and NKA to induce the depolarization of ventral roots. Electrical stimulation of the saphenous nerve with C-fiber strength evoked a depolarization lasting about 30 s of the ipsilateral L3 ventral root. This response, which is referred to as saphenous-nerve-evoked slow ventral root potential (VRP), was depressed by these NK1 receptor antagonists. In contrast, the saphenous-nerve-evoked slow VRP was potentiated by application of a mixture of peptidase inhibitors, including thiorphan, actinonin, and captopril in the presence of naloxone, but not after further addition of GR71251. Likewise, in the isolated coeliac ganglion of the guinea pig, electrical stimulation of the mesenteric nerves evoked in some ganglionic cells slow excitatory postsynaptic potentials (EPSPs), which were depressed by GR71251 and potentiated by peptidase inhibitors. These results further support the notion that SP and NKA serve as neurotransmitters producing slow EPSPs in the neonatal rat spinal cord and guinea pig prevertebral ganglia.Key words: substance P, neurokinin A, neurotransmitter, tachykinin antagonist, spinal cord.

scholarly journals Effects of antidromic stimulation of the ventral root on glucose utilization in the ventral horn of the spinal cord in the rat.

1987 ◽  
Vol 84 (15) ◽  
pp. 5492-5495 ◽  
Author(s):  
M. Kadekaro ◽  
W. H. Vance ◽  
M. L. Terrell ◽  
H. Gary ◽  
H. M. Eisenberg ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Glucose Utilization ◽  
Ventral Horn ◽  
Ventral Root ◽  
Antidromic Stimulation ◽  
Stimulation Of

Optical Mapping of Neural Network Activity in Chick Spinal Cord at an Intermediate Stage of Embryonic Development

1999 ◽  
Vol 81 (4) ◽  
pp. 1889-1902 ◽  
Author(s):  
Yoshiyasu Arai ◽  
Yoko Momose-Sato ◽  
Katsushige Sato ◽  
Kohtaro Kamino
Keyword(s):  
Neural Network ◽  
Spinal Cord ◽  
Action Potential ◽  
Intermediate Stage ◽  
Spinal Nerve ◽  
Ventral Root ◽  
Network Activity ◽  
Optical Signals ◽  
Fast Spike ◽  
Chick Spinal Cord

Optical mapping of neural network activity in chick spinal cord at an intermediate stage of embryonic development. We have applied multiple-site optical recording of transmembrane potential changes to recording of neuronal pathway/network activity from embryonic chick spinal cord slice preparations. Spinal cord preparations were dissected from 8-day-old chick embryos at Hamburger-Hamilton stage 33, and transverse slice preparations were prepared with the 13th cervical spinal nerve or with the 2nd or 5th lumbosacral spinal nerve intact. The slice preparations were stained with a voltage-sensitive merocyanine-rhodanine dye (NK2761). Transmembrane voltage-related optical (dye-absorbance) changes evoked by spinal nerve stimulation with positive square-current pulses using a suction electrode were recorded simultaneously from many loci in the preparation, using a 128- or 1,020-element photodiode array. Optical responses were detected from dorsal and ventral regions corresponding to the posterior (dorsal) and anterior (ventral) gray horns. The optical signals were composed of two components, fast spike-like and slow signals. In the dorsal region, the fast spike-like signal was identified as the presynaptic action potential in the sensory nerve and the slow signal as the postsynaptic potential. In the ventral region, the fast spike-like signal reflects the antidromic action potential in motoneurons, and the slow signal is related to the postsynaptic potential evoked in the motoneuron. In preparations in which the ventral root was cut microsurgically, the antidromic action potential-related optical signals were eliminated. The areas of the maximal amplitude of the evoked signals in the dorsal and ventral regions were located near the dorsal root entry zone and the ventral root outlet zone, respectively. Quasiconcentric contour-line maps were obtained in the dorsal and ventral regions, suggesting the functional arrangement of the dorsal and ventral synaptic connections. Synaptic fatigue induced by repetitive stimuli in the ventral synapses was more rapid than in the dorsal synapses. The distribution patterns of the signals were essentially similar among C13, LS2, and LS5 preparations, suggesting that there is no difference in the spatiotemporal pattern of the neural responses along the rostrocaudal axis of the spinal cord at this developmental stage. In the ventral root-cut preparations, comparing the delay times between the ventral slow optical signals, we have been able to demonstrate that neural network-related synaptic connections are generated functionally in the embryonic spinal cord at Hamburger-Hamilton stage 33.

scholarly journals Comparison of the Effects on Spinal Reflexes of Acetylsalicylate and Metamizol in Spinalized and Normal Rats

2005 ◽  
Vol 48 (3-4) ◽  
pp. 149-152
Author(s):  
Osman Genç ◽  
Sebahat Turgut ◽  
Günfer Turgut ◽  
Selim Kortunay
Keyword(s):  
Spinal Cord ◽  
Arachidonic Acid ◽  
Nonsteroidal Antiinflammatory Drugs ◽  
Ventral Root ◽  
Spinal Reflexes ◽  
Reflex Response ◽  
Antiinflammatory Drugs ◽  
Lumbosacral Region ◽  
Adult Rats ◽  
Stimulation Of

The effects of nonsteroidal antiinflammatory drugs, acetylsalicylate and metamizol, on spinal monosynaptic reflexes were investigated in spinalized and normal rats. Adult rats (n=36) weighing 150–200 g were anesthetized with ketamine and artificially ventilated. Half of rats were spinalized at C1 level. A laminectomy was performed in the lumbosacral region. Following electrical stimulation of the sciatic nerve by single pulses, reflex potentials were recorded from the ipsilateral L5 ventral root. Acetylsalicylate was administered orally (100 mg/kg for both spinalized and normal rats). Metamizol was administered intramuscularly (15 mg/kg for both spinalized and normal rats). These drug administrations significantly decreased the amplitude of reflex response in all groups (p<0.05). These data verify that observed inhibition by acetylsalicylicate and metamizol may be at the level of spinal cord. Also we suggested that the cyclooxygenase products of arachidonic acid may play an important role in regulating the reflex potential.

Dopamine exerts activation-dependent modulation of spinal locomotor circuits in the neonatal mouse

2012 ◽  
Vol 108 (12) ◽  
pp. 3370-3381 ◽  
Author(s):  
Jennifer M. Humphreys ◽  
Patrick J. Whelan
Keyword(s):  
Spinal Cord ◽  
Feedback Loops ◽  
Ventral Root ◽  
Neonatal Mouse ◽  
Network Activity ◽  
Mouse Spinal Cord ◽  
Network Function ◽  
Renshaw Cell ◽  
Root Stimulation ◽  
Excitatory Drive

Monoamines can modulate the output of a variety of invertebrate and vertebrate networks, including the spinal cord networks that control walking. Here we examined the multiple changes in the output of locomotor networks induced by dopamine (DA). We found that DA can depress the activation of locomotor networks in the neonatal mouse spinal cord following ventral root stimulation. By examining disinhibited rhythms, where the Renshaw cell pathway was blocked, we found that DA depresses a putative recurrent excitatory pathway that projects onto rhythm-generating circuitry of the spinal cord. This depression was D2 but not D1 receptor dependent and was not due exclusively to depression of excitatory drive to motoneurons. Furthermore, the depression in excitation was not dependent on network activity. We next compared the modulatory effects of DA on network function by focusing on a serotonin and a N-methyl-dl-aspartate-evoked rhythm. In contrast to the depressive effects on a ventral root-evoked rhythm, we found that DA stabilized a drug-evoked rhythm, reduced the frequency of bursting, and increased amplitude. Overall, these data demonstrate that DA can potentiate network activity while at the same time reducing the gain of recurrent excitatory feedback loops from motoneurons onto the network.

Modulation of Cellular and Synaptic Variability in the Lamprey Spinal Cord

2007 ◽  
Vol 97 (1) ◽  
pp. 44-56 ◽  
Author(s):  
David Parker ◽  
Sarah Bevan
Keyword(s):  
Spinal Cord ◽  
Substance P ◽  
Motor Neurons ◽  
Network Activity ◽  
Inhibitory Interneurons ◽  
Additional Source ◽  
Mean Values ◽  
Different Types ◽  
Network Properties ◽  
Synaptic Variability

Variability is increasingly recognized as a characteristic feature of cellular, synaptic, and network properties. While studies have traditionally focused on mean values, significant effects can result from changes in variance. This study has examined cellular and synaptic variability in the lamprey spinal cord and its modulation by the neuropeptide substance P. Cellular and synaptic variability differed in different types of cell and synapse. Substance P reduced the variability of subthreshold locomotor-related depolarizations and spiking in motor neurons during network activity. These effects were associated with a reduction in the variability of spiking in glutamatergic excitatory network interneurons and with a reduction in the variance of excitatory interneuron-evoked excitatory postsynaptic potentials (EPSPs). Substance P also reduced the variance of postsynpatic potentials (PSPs) from crossing inhibitory and excitatory interneurons, but it increased the variance of inhibitory postsynpatic potentials (IPSPs) from ipsilateral inhibitory interneurons. The effects on the variance of different PSPs could occur with or without changes in the PSP amplitude. The reduction in the variance of excitatory interneuron-evoked EPSPs was protein kinase A, calcium, and N-methyl-d-aspartate (NMDA) dependent. The NMDA dependence suggested that substance P was acting postsynaptically. This was supported by the reduced variability of postsynaptic responses to glutamate by substance P. However, ultrastructural analyses suggested that there may also be a presynaptic component to the modulation, because substance P reduced the variability of synaptic vesicle diameters in putative glutamatergic terminals. These results suggest that cellular and synaptic variability can be targeted for modulation, making it an additional source of spinal cord plasticity.

scholarly journals Effective reinnervation of the quadriceps femoris by spinal ventral root cross-anastomosis in rats

2012 ◽  
Vol 27 (5) ◽  
pp. 330-337 ◽  
Author(s):  
Chao Song ◽  
Gui-bin Zhong ◽  
Zu-de Liu ◽  
Wei Li ◽  
Peng-wen Ni ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Quadriceps Femoris ◽  
Retrograde Tracing ◽  
Ventral Root ◽  
Significant Difference ◽  
Before And After ◽  
Electrophysiological Examination ◽  
The Right ◽  
Spinal Cord Hemisection ◽  
Stimulation Of

PURPOSE: To study the effective recovery of the quadriceps femoris by spinal ventral root cross-anastomosis in rats. METHODS: End-to-end anastomosis was performed between the left L1 and L3 ventral roots using autogenous nerve graft ,and the right L1 and L3 roots were left intact. In control animals, the left L3 ventral root was cut and shortened, and anastomosis was not performed. Six months postoperatively, the movement of low extremities was detected by electrophysiological examination, hindlimb locomotion and basso, beattie and bresnahan (BBB) scoring at one, three, seven, 14, 21 and 28 days after SCI. Fluorescence retrograde tracing with TRUE BLUE (TB) and HE staining were performed to observe the nerve regeneration. RESULTS: Six months after surgery, the anastomotic nerve was smooth and not atrophic. The amplitudes of action potential were 7.63±1.86 mV and 6.0±1.92 mV respectively before and after the spinal cord hemisection. The contraction of left quadriceps femoris was induced by a single stimulation of the anastomotic nerve. The locomotion of left hindlimb was partially restored after spinal cord hemisection while creeping and climbing. In addition, there was significant difference in the BBB score at one, three and seven days after SCI. TB retrograde tracing and neurophysiologic observation indicated efficient reinnervation of the quadriceps femoris. CONCLUSION: The cross-anastomosis between spinal ventral root can partially reconstruct the function of quadriceps femoris following SCI and may have clinical implication for the treatment of human SCI.

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