scholarly journals Reticulospinal Neurons Receive Direct Spinobulbar Inputs During Locomotor Activity in Lamprey

2004 ◽  
Vol 92 (3) ◽  
pp. 1384-1390 ◽  
Author(s):  
James F. Einum ◽  
James T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Locomotor Activity ◽  
Brain Stem ◽  
Oscillation Amplitude ◽  
Ringer Solution ◽  
Experimental Chamber ◽  
Potential Oscillations ◽  
Reticulospinal Neurons

Reticulospinal neurons of the lamprey brain stem receive rhythmic input from the spinal cord during locomotor activity. The goal of the present study was to determine whether such spinal input has a direct component to reticulospinal neurons or depends on brain stem interneurons. To answer this question, an in vitro lamprey brain stem-spinal cord preparation was used with a diffusion barrier placed caudal to the obex, separating the experimental chamber into two baths. Locomotor activity was induced in the spinal cord by perfusion of d-glutamate or N-methyl-dl-aspartate into the spinal cord bath. The brain stem bath was first perfused with normal Ringer solution followed by a high-Ca2+, -Mg2+ solution, which reduced polysynaptic transmission. The amplitudes of membrane potential oscillations of reticulospinal neurons in the posterior and middle rhombencephalic reticular nuclei (PRRN and MRRN, respectively) recorded with sharp intracellular microelectrodes did not significantly change from normal to high-divalent solution. This finding suggests a large part of the spinal input creating the oscillations is direct to the reticulospinal neurons. Application of strychnine to the high-Ca2+, -Mg2+ solution decreased membrane potential oscillation amplitude, and injection of Cl− reversed presumed inhibitory postsynaptic potentials, indicating a role for direct spinal inhibitory inputs. Although reduced, the persistence of oscillations in strychnine suggests that spinal excitatory inputs also contribute to the oscillations. Thus it was concluded that both excitatory and inhibitory spinal neurons provide direct rhythmic inputs to reticulospinal cells of the PRRN and MRRN during locomotor activity. These inputs provide reticulospinal cells with information regarding the activity of the spinal locomotor networks.

scholarly journals Membrane Potential Oscillations in Reticulospinal and Spinobulbar Neurons During Locomotor Activity

2005 ◽  
Vol 94 (1) ◽  
pp. 273-281 ◽  
Author(s):  
James F. Einum ◽  
James T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Locomotor Activity ◽  
Brain Stem ◽  
Excitatory Amino Acid ◽  
Rhythmic Activity ◽  
Ventral Root ◽  
Potential Oscillations ◽  
Bath Application ◽  
The Brain

Feedback from the spinal locomotor networks provides rhythmic modulation of the membrane potential of reticulospinal (RS) neurons during locomotor activity. To further understand the origins of this rhythmic activity, the timings of the oscillations in spinobulbar (SB) neurons of the spinal cord and in RS neurons of the posterior and middle rhombencephalic reticular nuclei were measured using intracellular microelectrode recordings in the isolated brain stem-spinal cord preparation of the lamprey. A diffusion barrier constructed just caudal to the obex allowed induction of locomotor activity in the spinal cord by bath application of an excitatory amino acid to the spinal bath. All of the ipsilaterally projecting SB neurons recorded had oscillatory membrane potentials with peak depolarizations in phase with the ipsilateral ventral root bursts, whereas the contralaterally projecting SB neurons were about evenly divided between those in phase with the ipsilateral ventral root bursts and those in phase with the contralateral bursts. In the brain stem under these conditions, 75% of RS neurons had peak depolarizations in phase with the ipsilateral ventral root bursts while the remainder had peak depolarizations during the contralateral bursts. Addition of a high-Ca2+, Mg2+ solution to the brain stem bath to reduce polysynaptic activity had little or no effect on oscillation timing in RS neurons, suggesting that direct inputs from SB neurons make a major contribution to RS neuron oscillations under these conditions. Under normal conditions when the brain is participating in the generation of locomotor activity, these spinal inputs will be integrated with other inputs to RS neurons.

Identification of excitatory interneurons contributing to generation of locomotion in lamprey: structure, pharmacology, and function

1989 ◽  
Vol 62 (1) ◽  
pp. 59-69 ◽  
Author(s):  
J. T. Buchanan ◽  
S. Grillner ◽  
S. Cullheim ◽  
M. Risling
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Excitatory Amino Acid ◽  
Postsynaptic Membrane ◽  
Fictive Locomotion ◽  
Potential Oscillations ◽  
And Function ◽  
Spherical Vesicles ◽  
Membrane Potential Oscillations

1. In the in vitro preparation of the lamprey spinal cord, paired intracellular recordings of membrane potential were used to identify interneurons producing excitatory postsynaptic potentials (EPSPs) on myotomal motoneurons. 2. Seventy-nine interneurons (8.4% of all neuron-motoneuron pairs tested) elicited unitary EPSPs that followed one-for-one at short, constant latencies and were therefore considered monosynaptic according to conventional criteria. Evidence was obtained for selectivity and divergence of excitatory interneuron (EIN) outputs and for convergence of EIN input to motoneurons. 3. The neurotransmitter released by EINs may be an excitatory amino acid such as glutamate, because the EPSPs were depressed by antagonists of excitatory amino acids. 4. Intracellular dye injection revealed that EINs have small cell bodies (average 11 x 27 microns), transversely oriented dendrites, and thin (less than 3 microns) slowly conducting axons (0.7 m/s) that project caudally and ipsilaterally. One EIN exhibited a system of thin multi-branching axon collaterals with periodic swellings. Ultrastructurally, these swellings contained clear spherical vesicles, and they apposed postsynaptic membrane specializations. 5. During fictive locomotion, the membrane-potential oscillations of EINs were greater in amplitude than, but similar in shape and timing to, those of their postsynaptic motoneurons. EINs fired action potentials during fictive locomotion and contributed to the depolarization of motoneurons. 6. These interneurons are proposed to be a source of excitation to motoneurons and interneurons in the lamprey spinal cord, participating in motor activity including locomotion.

Activities of spinal neurons during brain stem-dependent fictive swimming in lamprey

1995 ◽  
Vol 73 (1) ◽  
pp. 80-87 ◽  
Author(s):  
J. T. Buchanan ◽  
S. Kasicki
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Brain Stem ◽  
Cell Types ◽  
Inhibitory Neurons ◽  
Spinal Neurons ◽  
Potential Oscillations ◽  
Electrical Shocks ◽  
Dorsal Cells ◽  
Membrane Potential Oscillations

1. We made intracellular microelectrode recordings of membrane potential from spinal neurons during fictive swimming elicited by brief electrical shocks to the spinal cord in a brain stem-spinal cord preparation of the adult silver lamprey (Ichthyomyzon unicuspis). 2. We characterized membrane potential activities recorded during brain stem-dependent fictive swimming in five spinal cell types: myotomal motoneurons, lateral interneurons (inhibitory neurons with ipsilateral descending axons), CC interneurons (neurons with contralateral and caudal projecting axons), edge cells (intraspinal stretch receptors), and dorsal cells (primary mechanosensory neurons with cell bodies in the spinal cord). The membrane potential activities were compared with data from previous reports recorded during fictive swimming in the isolated spinal cord with fictive swimming induced by superfusion with D-glutamate. 3. Compared with the same cell types recorded during D-glutamate-induced fictive swimming in brain stem-dependent fictive swimming, the motoneurons and CC interneurons had significantly larger trough-to-peak amplitudes of membrane potential oscillations, whereas lateral interneurons were not significantly different in amplitude. The timings of the membrane potential oscillations and of cell spiking were not significantly different in the two preparations, with the exception that motoneurons in brain stem-dependent fictive swimming were significantly earlier by approximately 10% of a cycle. Edge cells had only weak or no oscillatory activities, and dorsal cells had no detectable input during brain stem-dependent fictive swimming. These findings are similar to those in D-glutamate-induced fictive swimming.(ABSTRACT TRUNCATED AT 250 WORDS)

Time course of locomotor recovery and functional regeneration in spinal cord-transected lamprey: in vitro preparations

1994 ◽  
Vol 72 (2) ◽  
pp. 847-860 ◽  
Author(s):  
A. D. McClellan
Keyword(s):  
Spinal Cord ◽  
Locomotor Activity ◽  
Brain Stem ◽  
Time Course ◽  
Behavioral Recovery ◽  
Locomotor Function ◽  
Relay Systems ◽  
Functional Regeneration ◽  
Descending Projections

1. Previous studies indicate that after transection of the rostral spinal cord, larval lamprey begin to recover locomotor behavior 2 wk posttransection and recovery is complete at approximately 8 wk. To examine the mechanisms underlying behavioral recovery after spinal cord transection, in the present study the time course and extent of recovery of locomotor function was examined in in vitro brain/spinal cord preparations. With these preparations the contributions of functional regeneration of descending brain stem projections to recovery of spinal locomotor function can be examined in the absence of mechanosensory inputs and descending propriospinal relay systems. 2. In in vitro preparations from normal lamprey, stimulation in brain stem locomotor regions resulted in direct descending activation of locomotor networks in the rostral, middle, and caudal spinal cord. 3. At 4 wk posttransection, in vitro locomotor activity was usually confined to the rostral spinal cord a few millimeters below the transection site. At 8 wk posttransection locomotor activity was present in both the rostral and middle spinal cord, and spinal locomotor networks at these levels could be directly activated by restored descending projections from the brain stem. 4. At 16–32 wk posttransection locomotor activity similar to that seen in normal animals was present along the spinal cord. Additional manipulations suggest that at 32 wk posttransection descending axons from brain stem command/initiation neurons had grown for relatively long distances and could directly activate the locomotor networks in the caudal spinal cord. At each recovery time examined the ranges of locomotor parameters (cycle time, burst proportion, and intersegmental phase lag) overlapped with those in normal animals. 5. In vitro locomotor activity in spinal cord-transected animals could be recorded at progressively more caudal levels below the transection site during the course of recovery. However, locomotor activity in in vitro preparations occurred for shorter distances below the lesion than in whole animals at comparable recovery times. 6. Our recent double-labeling experiments suggest that behavioral recovery in spinal cord-transected lamprey is largely due to true regeneration of preexisting descending axons rather than development of new descending projections. Thus, these results in conjunction with our behavioral, in vitro, and anatomic data suggest that functional regeneration of descending axons from the brain, as well as other mechanisms such as descending propriospinal relay systems and mechanosensory inputs, account for the gradual restoration of locomotor function in spinal cord-transected lamprey.

scholarly journals Fictive Rhythmic Motor Patterns Induced by NMDA in an In Vitro Brain Stem–Spinal Cord Preparation From an Adult Urodele

1999 ◽  
Vol 82 (2) ◽  
pp. 1074-1077 ◽  
Author(s):  
Isabelle Delvolvé ◽  
Pascal Branchereau ◽  
Réjean Dubuc ◽  
Jean-Marie Cabelguen
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Rhythm Generation ◽  
Motor Patterns ◽  
Rhythmic Motor ◽  
Bath Application ◽  
The Neural Networks ◽  
Ventral Roots ◽  
Pleurodeles Waltl

An in vitro brain stem–spinal cord preparation from an adult urodele ( Pleurodeles waltl) was developed in which two fictive rhythmic motor patterns were evoked by bath application of N-methyl-d-aspartate (NMDA; 2.5–10 μM) with d-serine (10 μM). Both motor patterns displayed left-right alternation. The first pattern was characterized by cycle periods ranging between 2.4 and 9.0 s (4.9 ± 1.2 s, mean ± SD) and a rostrocaudal propagation of the activity in consecutive ventral roots. The second pattern displayed longer cycle periods (8.1–28.3 s; 14.2 ± 3.6 s) with a caudorostral propagation. The two patterns were inducible after a spinal transection at the first segment. Preliminary experiments on small pieces of spinal cord further suggested that the ability for rhythm generation is distributed along the spinal cord of this preparation. This study shows that the in vitro brain stem–spinal cord preparation from Pleurodeles waltl may be a useful model to study the mechanisms underlying the different axial motor patterns and the flexibility of the neural networks involved.

Neurochemical excitation of propriospinal neurons facilitates locomotor command signal transmission in the lesioned spinal cord

2011 ◽  
Vol 105 (6) ◽  
pp. 2818-2829 ◽  
Author(s):  
Eugene Zaporozhets ◽  
Kristine C. Cowley ◽  
Brian J. Schmidt
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Signal Transmission ◽  
Cholinergic Receptor ◽  
Neonatal Rat ◽  
Receptor Antagonists ◽  
Ion Removal ◽  
Propriospinal Neurons ◽  
Command Signal

Previous studies of the in vitro neonatal rat brain stem-spinal cord showed that propriospinal relays contribute to descending transmission of a supraspinal command signal that is capable of activating locomotion. Using the same preparation, the present series examines whether enhanced excitation of thoracic propriospinal neurons facilitates propagation of the locomotor command signal in the lesioned spinal cord. First, we identified neurotransmitters contributing to normal endogenous propriospinal transmission of the locomotor command signal by testing the effect of receptor antagonists applied to cervicothoracic segments during brain stem-induced locomotor-like activity. Spinal cords were either intact or contained staggered bilateral hemisections located at right T1/T2 and left T10/T11 junctions designed to abolish direct long-projecting bulbospinal axons. Serotonergic, noradrenergic, dopaminergic, and glutamatergic, but not cholinergic, receptor antagonists blocked locomotor-like activity. Approximately 73% of preparations with staggered bilateral hemisections failed to generate locomotor-like activity in response to electrical stimulation of the brain stem alone; such preparations were used to test the effect of neuroactive substances applied to thoracic segments (bath barriers placed at T3 and T9) during brain stem stimulation. The percentage of preparations developing locomotor-like activity was as follows: 5-HT (43%), 5-HT/ N-methyl-d-aspartate (NMDA; 33%), quipazine (42%), 8-hydroxy-2-(di- n-propylamino)tetralin (20%), methoxamine (45%), and elevated bath K+ concentration (29%). Combined norepinephrine and dopamine increased the success rate (67%) compared with the use of either agent alone (4 and 7%, respectively). NMDA, Mg2+ ion removal, clonidine, and acetylcholine were ineffective. The results provide proof of principle that artificial excitation of thoracic propriospinal neurons can improve supraspinal control over hindlimb locomotor networks in the lesioned spinal cord.

Rhythmic sympathetic nerve discharges in an in vitro neonatal rat brain stem-spinal cord preparation

1999 ◽  
Vol 87 (3) ◽  
pp. 1066-1074 ◽  
Author(s):  
Chun-Kuei Su
Keyword(s):  
Spinal Cord ◽  
Ascorbic Acid ◽  
Brain Stem ◽  
Sympathetic Nerve ◽  
Power Spectral Analysis ◽  
Neural Mechanisms ◽  
Neonatal Rat ◽  
Root Activity ◽  
Superior Cerebellar Artery

To understand the origination of sympathetic nerve discharge (SND), I developed an in vitro brain stem-spinal cord preparation from neonatal rats. Ascorbic acid (3 mM) was added into the bath solution to increase the viability of preparations. At 24°C, rhythmic SND (recorded from the splanchnic nerve) was consistently observed, but it became quiescent at <16°C. Respiratory-related SND (rSND) was discernible and was well correlated with C4 root activity. Power spectral analysis of SND revealed a dominant 2-Hz oscillation. In most preparations (86%), such oscillation was persistent, whereas it only slightly reduced its magnitude after isolation from the brain stem. The removal of neural structures rostral to the superior cerebellar artery (equivalent to the level of facial nuclei) reduced rSND, increased tonic SND, but did not affect the temporal coupling between SND and C4 root activity. Our data suggest a prominent contribution of SND from the neural mechanisms confined within the neonatal rat spinal cord. This ascorbic acid-enhanced in vitro preparation is a very useful model to study neural mechanisms underlying sympathorespiratory integration.

In vitro microelectrode study of the electrical properties of smooth muscle in equine ileum

2001 ◽  
Vol 149 (23) ◽  
pp. 707-711 ◽  
Author(s):  
N. P. H. Hudson ◽  
I. G. Mayhew ◽  
G. T. Pearson
Keyword(s):  
Smooth Muscle ◽  
Membrane Potential ◽  
Smooth Muscle Cells ◽  
Longitudinal Muscle ◽  
Muscle Cells ◽  
Muscle Layer ◽  
Potential Oscillations ◽  
Longitudinal Muscle Layer ◽  
Membrane Potential Oscillations

Intracellular microelectrode recordings were made from smooth muscle cells in cross-sectional preparations of equine ileum, superfused in vitro. Membrane potential oscillations and spike potentials were recorded in all preparations, but recordings were made more readily from cells in the longitudinal muscle layer than from cells in the circular layer. The mean (se) resting membrane potential (RMP) of smooth muscle cells in the longitudinal muscle layer was -51.9 (1.2) mV, and the membrane potential oscillations in this layer had a mean amplitude of 4.8 (0.4) mV, a frequency of 9.0 (0.1) cycles per minute and a duration of 5.8 (0.2) seconds. The membrane potential oscillations were preserved in the presence of tetrodotoxin. A waxing and waning pattern of membrane potential oscillation activity was observed. Nifedipine abolished the spiking contractile activity of the smooth muscle, did not abolish the membrane potential oscillations but did alter their temporal characteristics.

Micturition reflexes in the in vitro neonatal rat brain stem-spinal cord-bladder preparation

1994 ◽  
Vol 266 (3) ◽  
pp. R658-R667 ◽  
Author(s):  
K. Sugaya ◽  
W. C. De Groat
Keyword(s):  
Spinal Cord ◽  
Electrical Stimulation ◽  
Brain Stem ◽  
Rat Brain ◽  
Bladder Wall ◽  
Spinal Reflex ◽  
Neonatal Rat ◽  
Evoked Contractions ◽  
Stimulation Of

An in vitro neonatal (1-7 day) rat brain stem-spinal cord-bladder (BSB) preparation was used to examine the central control of micturition. Isovolumetric bladder contractions occurred spontaneously or were induced by electrical stimulation of the ventrolateral brain stem, spinal cord, bladder wall (ES-BW), or by perineal tactile stimulation (PS). Transection of the spinal cord at the L1 segment increased the amplitude of ES-BW- and PS-evoked contractions, and subsequent removal of the spinal cord further increased spontaneous and ES-BW-evoked contractions but abolished PS-evoked contractions. Hexamethonium (1 mM), a ganglionic blocking agent, mimicked the effect of cord extirpation. Tetrodotoxin (1 microM) blocked ES-BW- and PS-evoked contractions but enhanced spontaneous contractions. Bicuculline methiodide (10-50 microM), a gamma-aminobutyric acid A receptor antagonist, increased the amplitude of spontaneous, ES-BW- and PS-evoked contractions. These results indicate that PS-evoked contractions are mediated by spinal reflex pathways, whereas spontaneous and ES-BW-evoked contractions that are elicited by peripheral mechanisms are subject to a tonic inhibition dependent on an efferent outflow from the spinal cord. PS-evoked micturition is also subject to inhibitory modulation arising from sites rostral to the lumbosacral spinal cord. Although electrical stimulation of bulbospinal excitatory pathways can initiate bladder contractions in the neonatal rat, these pathways do not appear to have an important role in controlling micturition during the first postnatal week.

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