Intrinsic Properties Shape the Firing Pattern of Ventral Horn Interneurons From the Spinal Cord of the Adult Turtle

2006 ◽  
Vol 96 (5) ◽  
pp. 2670-2677 ◽  
Author(s):  
Morten Smith ◽  
Jean-François Perrier
Keyword(s):  
Spinal Cord ◽  
Activity Patterns ◽  
Ventral Horn ◽  
Inward Rectification ◽  
Intrinsic Properties ◽  
Patch Clamp Technique ◽  
Firing Patterns ◽  
Pharmacological Tests ◽  
Low Threshold

Interneurons in the ventral horn of the spinal cord play a central role in motor control. In adult vertebrates, their intrinsic properties are poorly described because of the lack of in vitro preparations from the spinal cord of mature mammals. Taking advantage of the high resistance to anoxia in the adult turtle, we used a slice preparation from the spinal cord. We used the whole cell blind patch-clamp technique to record from ventral horn interneurons. We characterized their firing patterns in response to depolarizing current pulses and found that all the interneurons fired repetitively. They displayed bursting, adapting, delayed, accelerating, or oscillating firing patterns. By combining electrophysiological and pharmacological tests, we showed that interneurons expressed slow inward rectification, plateau potential, voltage-sensitive transient outward rectification, and low-threshold spikes. These results demonstrate a diversity of intrinsic properties that may enable a rich repertoire of activity patterns in the network of ventral horn interneurons.

scholarly journals Endogenous Firing Patterns of Murine Spiral Ganglion Neurons

1997 ◽  
Vol 77 (3) ◽  
pp. 1294-1305 ◽  
Author(s):  
Zun-Li Mo ◽  
Robin L. Davis
Keyword(s):  
Action Potential ◽  
Spiral Ganglion ◽  
Constant Current ◽  
Inward Rectification ◽  
Spiral Ganglion Neurons ◽  
Patch Clamp Technique ◽  
Firing Patterns ◽  
Spike Amplitude ◽  
Ganglion Neurons

Mo, Zun-Li and Robin L. Davis. Endogenous firing patterns of murine spiral ganglion neurons. J. Neurophysiol. 77: 1294–1305, 1997. Current-clamp recordings with the use of the whole cell configuration of the patch-clamp technique were made from postnatal mouse spiral ganglion neurons in vitro. Cultures contained neurons that displayed monopolar, bipolar, and pseudomonopolar morphologies. Additionally, a class of neurons having exceptionally large somata was observed. Frequency histograms of the maximum number of action potentials fired from 240-ms step depolarizations showed that neurons could be classified as either slowly adapting or rapidly adapting. Most neurons (85%) were in the rapidly adapting category (58 of 68 recordings). Measurements of elementary properties were used to define the endogenous firing characteristics of both neuron classes. Action potential number varied with step and holding potential, spike amplitude decayed during prolonged depolarizations, and spike frequency adaptation was observed in both rapidly and slowly adapting neurons. The apparent input resistance, spike amplitude decrement, and instantaneous firing frequency differed significantly between rapidly and slowly adapting neurons. Inward rectification was evaluated in response to hyperpolarizing constant current injections. Present in both electrophysiological classes, its magnitude was graded from neuron to neuron, reflecting differences in number, type, and/or voltage dependence of the underlying channels. These data suggest that spiral ganglion neurons possess intrinsic firing properties that regulate action potential number and timing, features that may be crucial to signal coding in the auditory periphery.

scholarly journals Windup of Nociceptive Flexion Reflex Depends on Synaptic and Intrinsic Properties of Dorsal Horn Neurons in Adult Rat

2019 ◽  
Author(s):  
Franck Aby ◽  
Rabia Bouali-Benazzouz ◽  
Marc Landry ◽  
Pascal Fossat
Keyword(s):  
Spinal Cord ◽  
Progressive Increase ◽  
Ventral Horn ◽  
Intrinsic Properties ◽  
Calcium Dependent ◽  
Adult Rat ◽  
Dorsal Horn Neurons ◽  
Nociceptive Flexion Reflex

Windup, a progressive increase in spinal response to repetitive stimulations of nociceptive peripheral fibres, is a useful model to study central sensitization to pain. Windup is expressed by neurons in of both dorsal and ventral horn of the spinal cord. In juvenile rats, it has been demonstrated both in vivo and in vitro that windup depends on calcium-dependent intrinsic properties and their modulation by synaptic components. However, the involvement of these two components in the adult remain controversial. In the present study, by means of electromyographic and extracellular recordings, we show that windup in adult, in vivo, depends on a synaptic balance between excitatory NMDA receptors and inhibitory glycinergic receptors. We also demonstrate the involvement of L-type calcium channels in both the dorsal and ventral horn of the spinal cord. These results indicate that windup in adults is similar to juveniles rats and that windup properties are the same regardless spinal network, i.e. sensory or motor.

scholarly journals Windup of Nociceptive Flexion Reflex Depends on Synaptic and Intrinsic Properties of Dorsal Horn Neurons in Adult Rats

2019 ◽  
Vol 20 (24) ◽  
pp. 6146
Author(s):  
Franck Aby ◽  
Rabia Bouali-Benazzouz ◽  
Marc Landry ◽  
Pascal Fossat
Keyword(s):  
Spinal Cord ◽  
Progressive Increase ◽  
Ventral Horn ◽  
Intrinsic Properties ◽  
Adult Rats ◽  
Juvenile Rats ◽  
Calcium Dependent ◽  
Nociceptive Flexion Reflex

Windup, a progressive increase in spinal response to repetitive stimulations of nociceptive peripheral fibers, is a useful model to study central sensitization to pain. Windup is expressed by neurons in both the dorsal and ventral horn of the spinal cord. In juvenile rats, it has been demonstrated both in vivo and in vitro that windup depends on calcium-dependent intrinsic properties and their modulation by synaptic components. However, the involvement of these two components in the adults remains controversial. In the present study, by means of electromyographic and extracellular recordings, we show that windup in adults, in vivo, depends on a synaptic balance between excitatory N-methyl-D-aspartate (NMDA) receptors and inhibitory glycinergic receptors. We also demonstrate the involvement of L-type calcium channels in both the dorsal and ventral horn of the spinal cord. These results indicate that windup in adults is similar to juvenile rats and that windup properties are the same regardless of the spinal network, i.e., sensory or motor.

scholarly journals Presynaptic Angiotensin II AT1 Receptors Enhance Inhibitory and Excitatory Synaptic Neurotransmission to Motoneurons and Other Ventral Horn Neurons in Neonatal Rat Spinal Cord

2005 ◽  
Vol 94 (2) ◽  
pp. 1405-1412 ◽  
Author(s):  
Murat Oz ◽  
Keun-Hang Yang ◽  
Michael J. O'Donovan ◽  
Leo P. Renaud
Keyword(s):  
Spinal Cord ◽  
Angiotensin Ii ◽  
Ventral Horn ◽  
Synaptic Activity ◽  
Neonatal Rat ◽  
Ang Ii ◽  
Synaptic Neurotransmission ◽  
Excitatory Neurotransmission ◽  
Ventral Spinal Cord

In neonatal spinal cord, we previously reported that exogenous angiotensin II (ANG II) acts at postsynaptic AT1 receptors to depolarize neonatal rat spinal ventral horn neurons in vitro. This study evaluated an associated increase in synaptic activity. Patch clamp recordings revealed that 38/81 thoracolumbar (T7–L5) motoneurons responded to bath applied ANG II (0.3–1 μM; 30 s) with a prolonged (5–10 min) and reversible increase in spontaneous postsynaptic activity, selectively blockable with Losartan ( n = 5) but not PD123319 ( n = 5). ANG-II-induced events included both spontaneous inhibitory (IPSCs; n = 6) and excitatory postsynaptic currents (EPSCs; n = 5). While most ANG induced events were tetrodotoxin-sensitive, ANG induced a significant tetrodotoxin-resistant increase in frequency but not amplitude of miniature IPSCs ( n = 7/13 cells) and EPSCs ( n = 2/7 cells). In 35/77 unidentified neurons, ANG II also induced a tetrodotoxin-sensitive and prolonged increase in their spontaneous synaptic activity that featured both IPSCs ( n = 5) and EPSCs ( n = 4) when tested in the presence of selective amino acid receptor antagonists. When tested in the presence of tetrodotoxin, ANG II was noted to induce a significant increase in the frequency but not the amplitude of mIPSCs ( n = 9) and mEPSCs ( n = 8). ANG also increased spontaneous motor activity from isolated mouse lumbar ventral rootlets. Collectively, these observations support the existence of a wide pre- and postsynaptic distribution of ANG II AT1 receptors in neonatal ventral spinal cord that are capable of influencing both inhibitory and excitatory neurotransmission.

Development of ionic conductances in neurons of neurons of the inferior olive in the rat: an in vitro study

1988 ◽  
Vol 234 (1275) ◽  
pp. 199-218 ◽  
Keyword(s):  
Membrane Potential ◽  
Inferior Olive ◽  
Early Period ◽  
In Vitro Study ◽  
Inward Rectification ◽  
High Threshold ◽  
Ca Channel ◽  
Ionic Conductances ◽  
Low Threshold

Neurons of the inferior olive of the rat were studied at different stages of their postnatal (PN) development by using the current clamp technique in slices maintained in vitro . Antidromic and synaptic activation of inferior olivary neurons could be achieved in preparations as young as PN day 2. Neurons at this age already exhibited a variety of ionic conductances which included fast sodium-dependent spikes, high-threshold and low-threshold calcium spikes, potassium-dependent currents, Ca-dependent after-hyperpolarizing potentials (AHPS), and both instan­taneous and time-dependent inward rectification at hyperpolarized levels of membrane potential. The two types of Ca-dependent responses recorded in olivary neurons during the first postnatal week were graded with the magnitude of the depolarization imposed on the cells. Further­more, the high-threshold Ca spikes were only clearly observed during this early period when K conductances were depressed by the injection of caesium into the cells or by bath application of 4-aminopyridine. In contrast, the high-threshold Ca spikes could be obtained without sup­pression of K currents and were all-or-none in character in some neurons after PN day 8 and in all neurons after PN day 11. The observations suggest that the balance between K and Ca currents changes throughout maturation and is largely in favour of the K current until about the end of the first PN week. At all ages studied, the low-threshold Ca spikes were much less sensitive to the Ca channel blocker cadmium than were the high-threshold Ca spikes. Finally, spontaneous, regular oscillations of the membrane potential were observed for the first time at PN day 16 and were only commonly observed after PN day 19, suggesting a late develop­ment of electrotonic coupling between olivary neurons.

scholarly journals Glycinergic Miniature Synaptic Currents and Receptor Cluster Sizes Differ Between Spinal Cord Interneurons

1999 ◽  
Vol 82 (1) ◽  
pp. 312-319 ◽  
Author(s):  
Sharon Oleskevich ◽  
Francisco J. Alvarez ◽  
Bruce Walmsley
Keyword(s):  
Spinal Cord ◽  
Glycine Receptor ◽  
Structural Features ◽  
Ventral Horn ◽  
Electrophysiological Recording ◽  
Rat Spinal Cord ◽  
Whole Cell Patch Clamp ◽  
Structural And Functional Properties ◽  
Receptor Clusters

The structural features of a synaptic connection between central neurons play an important role in determining the strength of the connection. In the present study, we have examined the relationship between the structural and functional properties of glycinergic synapses in the rat spinal cord. We have analyzed the structure of glycinergic receptor clusters on rat ventral horn interneurons using antibodies against the glycine receptor clustering protein, gephyrin. We have examined the properties of quantal glycinergic currents generated at these synapses using whole cell patch-clamp recordings of miniature postsynaptic inhibitory currents (mIPSCs) in rat spinal cord slices in vitro. Our immunolabeling results demonstrate that there is a considerable variability in the size of glycine receptor clusters within individual neurons. Furthermore there are large differences in the mean cluster size between neurons. These observations are paralleled closely by recordings of glycinergic mIPSCs. The mIPSC amplitude varies significantly within and between neurons. Results obtained using combined immunolabeling and electrophysiological recording on the same neurons show that cells with small glycine receptor clusters concurrently exhibit small mIPSCs. Our results suggest that the differences in the size of glycinergic receptor clusters may constitute an important factor contributing to the observed differences in mIPSC amplitude among spinal cord interneurons.

The development of voltege-dependent ionic conductances In murine spinal cord neurones in culture

1988 ◽  
Vol 66 (10) ◽  
pp. 1328-1336 ◽  
Author(s):  
C. Krieger ◽  
T. A. Sears
Keyword(s):  
Spinal Cord ◽  
Sodium Current ◽  
Potassium Conductance ◽  
Calcium Currents ◽  
Delayed Rectifier ◽  
Patch Clamp Technique ◽  
Calcium Dependent ◽  
Ionic Conductances ◽  
Voltage Dependent

The development of voltage-dependent ionic conductances of foetal mouse spinal cord neurones was examined using the whole-cell patch-clamp technique on neurones cultured from embryos aged 10–12 days (E10–E12) which were studied between the first day in vitro (V1) to V10. A delayed rectifier potassium conductance (IK) and a leak conductance were observed in neurones of E10.V1, E11, V1, and E12, V1 as well as in neurones cultured for longer periods. A rapidly activating and inactivating potassium conductance (IA) was seen in neurones from E11, V2 and E12, V1 and at longer times in vitro. A tetrodotoxin (TTX) sensitive sodium-dependent inward current was observed in neurones of E11 and E12 from V1 onwards. Calcium-dependent conductances were not detectable in these neurones unless the external calcium concentration was raised 10- to 20-foid and potassium conductances were blocked. Under these conditions calcium currents could be observed as early as E11, V3 and E12, V2 and at subsequent times in vitro. The pattern of development of voltage-dependent ionic conductances in murine spinal neurones is such that initially leak and potassium currents are present followed by sodium current and subsequently calcium current.

scholarly journals Autoactivity of A5 neurons: role of subthreshold oscillations and persistent Na+current

1997 ◽  
Vol 273 (5) ◽  
pp. H2280-H2289 ◽  
Author(s):  
Donghai Huangfu ◽  
Patrice G. Guyenet
Keyword(s):  
Membrane Potential ◽  
Discharge Rate ◽  
Input Resistance ◽  
Frequency Component ◽  
Inward Rectification ◽  
Intrinsic Properties ◽  
Potential Oscillations ◽  
Subthreshold Oscillations

A5 noradrenergic neurons play a key role in autonomic regulation, nociception, and respiration. The purpose of the present experiments was to characterize some of the intrinsic properties of A5 cells in vitro. Whole cell recordings were obtained from 85 spinally projecting neurons of the ventrolateral pons of neonate rats. Immunohistochemistry showed that 60% of the ventrolateral pontine cells were noradrenergic. Eighty percent of A5 neurons were spontaneously active (0.1–5.5 spikes/s). Their discharge rate was unchanged by a mixture of synaptic blockers that eliminated postsynaptic potentials (PSPs). The nonnoradrenergic cells could not be distinguished from A5 cells on the basis of discharge rate, action potential duration, inward rectification, input resistance, or accommodation. A5 cells displayed subthreshold irregular oscillations of the membrane potential (main frequency component 0.5–2 Hz). These oscillations were unchanged in the presence of low external Ca2+-high Mg2+ and were very reduced by hyperpolarizing the cells below −65 mV. The oscillations were partially attenuated by 1 μM tetrodotoxin (TTX) and were eliminated by reducing external Na+ (27 mM). Stepping the membrane potential from −65 to −50 mV for 200 ms revealed the presence of a transient and a persistent inward current that were both blocked by 0.1 μM TTX or by extracellular Na+ reduction. In conclusion, most A5 neurons are spontaneously active in vitro. They display irregular subthreshold membrane potential oscillations generated by voltage-activated conductances that include a persistent TTX-sensitive Na+ current. Most of the activity of A5 cells appears due to intrinsic properties rather than to synaptic inputs.

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