Differential effects of muscimol upon the firing frequency of large and small amplitude antidromic dorsal root action potentials in rat spinal cord in vitro

2002 ◽  
Vol 330 (2) ◽  
pp. 139-142 ◽  
Author(s):  
J. Bagust ◽  
W.D. Willis
Keyword(s):  
Spinal Cord ◽  
Action Potentials ◽  
Dorsal Root ◽  
Small Amplitude ◽  
Firing Frequency ◽  
Rat Spinal Cord ◽  
Differential Effects

The locomotor central pattern generator of the rat spinal cord in vitro is optimally activated by noisy dorsal root waveforms

2011 ◽  
Vol 106 (2) ◽  
pp. 872-884 ◽  
Author(s):  
Giuliano Taccola
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Central Pattern Generator ◽  
Dorsal Root ◽  
Spinal Injury ◽  
Cauda Equina ◽  
Pattern Generator ◽  
Rat Spinal Cord ◽  
Pharmacological Agents

The spinal cord contains an intrinsic locomotor program driven by a central pattern generator that rhythmically activates flexor and extensor limb motor pools. Although long-lasting locomotor activity can be generated pharmacologically, trains of afferent stimuli trigger only few locomotor cycles. The present study investigated whether a new electrical stimulation protocol (termed FL istim) could elicit long-lasting fictive locomotion (FL) in the rat spinal cord in vitro. Thus, after first inducing FL by bath application of N-methyl-d-aspartate and serotonin, the recorded waveform obtained from a lumbar ventral root was digitized and then applied to either a lumbar dorsal root or the cauda equina following washout of pharmacological agents. Two FL istim cycles were the threshold input to evoke an episode of FL from ventral roots. Longer cycles (up to 1 min) induced sustained FL (up to 1 min) with stereotyped periodicity (2.2 ± 0.5 s), despite changing frequency (2–4 s) or cycle amplitude of FL istim. Gradual filtering out of the noise from FL istim trace concomitantly decreased the efficiency of FL so that stimulation with equivalent pure sinusoids produced asynchronous, irregular discharges only that could not be converted to FL by adding spontaneous basal activity. This study is the first demonstration that epochs of rhythmic locomotor-like oscillations applied to a dorsal root represent an efficient stimulus to evoke FL as long as they contain the electrophysiological noise produced within FL cycles. These observations suggest novel strategies to improve the efficiency of electrical stimulation delivered by clinical devices for neurorehabilitation after spinal injury.

Spatiotemporal Patterns of Dorsal Root–Evoked Network Activity in the Neonatal Rat Spinal Cord: Optical and Intracellular Recordings

2005 ◽  
Vol 94 (3) ◽  
pp. 1952-1961 ◽  
Author(s):  
Lea Ziskind-Conhaim ◽  
Stephen Redman
Keyword(s):  
Spinal Cord ◽  
Action Potentials ◽  
Dorsal Root ◽  
Spatiotemporal Patterns ◽  
Neonatal Rat ◽  
Network Activity ◽  
Rat Spinal Cord ◽  
Optical Signals ◽  
Postsynaptic Potentials ◽  
Neuronal Ensembles

Spatiotemporal patterns of dorsal root–evoked potentials were studied in transverse slices of the rat spinal cord by monitoring optical signals from a voltage-sensitive dye with multiple-photodiode optic camera. Typically, dorsal root stimulation generated two basic waveforms of voltage images: dual-component images consisting of fast, spike-like signal followed by a slow signal in the dorsal horn, and small, slow signals in the ventral horn. To qualitatively relate the optical signals to membrane potentials, whole cell recordings were combined with measurements of light absorption in the area around the soma. The slow optical signals correlated closely with subthreshold postsynaptic potentials in all regions of the cord. The spike-like component was not associated with postsynaptic action potentials, suggesting that the fast signal was generated by presynaptic action potentials. Firing in a single neuron could not be detected optically, implying that local voltage images originated from synchronously activated neuronal ensembles. Blocking glutamatergic synaptic transmission inhibited excitatory postsynaptic potentials (EPSPs) and significantly reduced the slow optical signals, indicating that they were mediated by glutamatergic synapses. Suppressing glycine-mediated inhibition increased the amplitude of both optical signals and EPSPs, while blocking GABAA receptor–mediated synapses, increased the amplitude and time course of EPSPs and prolonged the duration of voltage images in larger areas of the slice. The close correlation between evoked EPSPs and their respective local voltage images shows the advantage of the high temporal resolution optical system in measuring both the spatiotemporal dynamics of segmental network excitation and integrated potentials of neuronal ensembles at identified sites.

Neuronal Bursting Induced by NK3 Receptor Activation in the Neonatal Rat Spinal Cord In Vitro

2001 ◽  
Vol 86 (6) ◽  
pp. 2939-2950 ◽  
Author(s):  
Cristina Marchetti ◽  
Andrea Nistri
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Dorsal Root ◽  
Extracellular Recording ◽  
Rhythmic Activity ◽  
Input Resistance ◽  
Receptor Activation ◽  
Neonatal Rat ◽  
Rat Spinal Cord

Intracellular recording from lumbar motoneurons and extracellular recording from ventral roots of the neonatal rat isolated spinal cord were used to study the mechanisms responsible for the excitation mediated by NK3 tachykinin receptors. The selective NK3 agonists senktide or [MePhe7]neurokinin B induced a slow depolarization with superimposed oscillations (mean period ± SD was 2.8 ± 0.8 s) that, in the majority of cases, showed left-right alternation at segmental level and were synchronous between L2 and L5 of the same side. During agonist wash out (5–20 min) a delayed form of hyperexcitability emerged consisting of bursts lasting 8 ± 2 s (average interburst interval 55 ± 21 s) with superimposed oscillations usually with homosegmental alternation and heterosegmental synchronicity. Such bursting was accompanied by depression of GABAergic dorsal root potentials evoked by dorsal root stimulation and of the recurrent inhibitory postsynaptic potential recorded from motoneurons. Despite bursting, motoneuron membrane potential returned to baseline while input resistance was increased. Bursts were a network-dependent phenomenon triggered by previous NK3 receptor activation because bursting was suppressed by glutamate receptor antagonists and was insensitive to motoneuron membrane potential or subsequent application of an NK3 receptor antagonist. NK3 receptors operated synergistically with N-methyl-d-aspartate (NMDA) and 5-hydroxytryptamine (5-HT) to trigger fully alternating locomotor-like rhythms while NK3 receptor antagonism disrupted the same rhythm. In summary, in the neonatal rat spinal cord NK3 receptors could trigger rhythmic activity predominantly with alternation at segmental level but with synchronous coupling between ipsilateral motor pools. NK3receptor activation could also facilitate fictive locomotor patterns induced by NMDA and 5-HT.

scholarly journals Neonatal Mice Spinal Cord Interneurons Sending Axons in Dorsal Roots

2020 ◽  
Author(s):  
Laura Paulina Osuna-Carrasco ◽  
Sergio Horacio Duenas-Jimenez ◽  
Carmen Toro-Castillo ◽  
Braniff De la Torre ◽  
Irene Aguilar-Garcia ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Action Potentials ◽  
Dorsal Root ◽  
Staining Technique ◽  
Spinal Cord Dorsal Horn ◽  
Monosynaptic Reflex ◽  
Primary Afferent Depolarization ◽  
Dorsal Roots ◽  
Dorsal Root Reflex

Abstract Background: Spinal cord interneurons send their axons in the dorsal root. Their antidromic fire could modulate peripheral receptors. Thus, it could control pain, other sensorial modality, or muscle spindle activity. In this study, we assessed a staining technique to analyze whether interneurons send axons in the neonate mouse’s dorsal roots. We conducted experiments in 10 Swiss-Webster mice, which ranged in age from 2 to 13 postnatal days. We dissected the spinal cord and studied it in vitro. Results: We observed interneurons in the spinal cord dorsal horn sending axons through dorsal roots. A mix of fluorochromes applied in dorsal roots marked these interneurons. They have a different morphology than motoneurons. Primary afferent depolarization in afferent terminals produces antidromic action potentials (dorsal root reflex; DRR). These reflexes appeared by stimulation of adjacent dorsal roots. We found that in the presence of bicuculline, DRR recorded in the L4 dorsal root evoked by L5 dorsal root stimulation was reduced. Simultaneously, the monosynaptic reflex (MR) in the L5 ventral root was not affected; nevertheless, a long-lasting after discharge appeared. The addition of 2-amino-5 phosphonovalric acid (AP5), an antagonist of NMDA receptors, abolished the MR without changing the after discharge. Action potentials persisted in dorsal roots even in low Ca2+ concentration. Conclusions: Thus, firing interneurons could send their axons by dorsal roots. Antidromic potentials may be characteristics of the neonatal mouse, probably disappearing in adulthood.

Depression of Windup of Spinal Neurons in the Neonatal Rat Spinal Cord In Vitro by an NK3 Tachykinin Receptor Antagonist

2001 ◽  
Vol 85 (4) ◽  
pp. 1502-1511 ◽  
Author(s):  
Mario Barbieri ◽  
Andrea Nistri
Keyword(s):  
Spinal Cord ◽  
Synaptic Transmission ◽  
Receptor Antagonist ◽  
Dorsal Root ◽  
Direct Action ◽  
Extracellular Recording ◽  
Neonatal Rat ◽  
Rat Spinal Cord ◽  
Tachykinin Receptor

The effects of the NK3 tachykinin receptor antagonist SR 142801 on synaptic transmission and spike windup induced by trains of stimuli applied to a dorsal root were investigated with intra- and extracellular recording from the neonatal rat spinal cord in vitro. SR 142801 (10 μM) reduced the depolarization (recorded from lumbar ventral roots) induced by senktide (an NK3 agonist) more strongly than the one evoked by substance P methyl ester (SPMeO; an NK1 agonist). Nevertheless, after a long (>2 h) application time, SR 142801 largely depressed the response to SPMeO as well. When NK1 or NK3 receptors were blocked by >50% in the presence of SR 142801, there was also a significant reduction in the cumulative depolarization induced by repeated stimuli to a single dorsal root. This blocking action by SR 142801 was also observed in the presence of the N-methyl-d-aspartate (NMDA) receptor antagonist d-aminophosphonovalerate (APV) and the calcium channel blocker nifedipine. Intracellular data from lumbar motoneurons showed that the spike windup was the first and most sensitive target for the SR 142801 blocking effect. Increasing stimulus strength to dorsal root fibers could partly surmount such a block. SR 142801 per se had no direct action on fast synaptic transmission, membrane potential, or input resistance. These findings indicate that SR 142801 could lead to an early, large reduction in the windup of action potential discharge by motoneurons, suggesting its ability to suppress the reflex component of central sensitization evoked by repeated dorsal root stimuli.

Sign in / Sign up

Export Citation Format

Share Document