Dopaminergic Modulation of Spinal Neurons and Synaptic Potentials in the Lamprey Spinal Cord

1997 ◽  
Vol 77 (1) ◽  
pp. 289-298 ◽  
Author(s):  
Christopher P. Kemnitz
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Cycle Period ◽  
Spinal Neurons ◽  
Postsynaptic Potentials ◽  
Giant Interneurons ◽  
Bath Application ◽  
Dopaminergic Modulation ◽  
Dorsal Cells ◽  
Stimulation Of

Kemnitz, Christopher P. Dopamineric modulation of spinal neurons and synaptic potentials in the lamprey spinal cord. J. Neurophysiol. 77: 289–298, 1997. It has been shown previously that dopamine-immunoreactive cells and processes are present in the lamprey spinal cord and that dopamine modulates the cycle period of fictive swimming. The present study was undertaken to further characterize the effects of dopamine on the cellular properties of lamprey spinal neurons and on inhibitory and excitatory postsynaptic potentials to determine how dopaminergic modulation may affect the central pattern generator for locomotion. Dopamine reduced the late afterhyperpolarization (late AHP) following the action potential of motoneurons, and in three types of sensory neurons: dorsal cells, edge cells, and giant interneurons. The late AHP was not reduced in lateral interneurons or CC interneurons, both of which are part of the central motor pattern generating neural network. The reduction of the late AHP in motoneurons, edge cells, and giant interneurons resulted in an increase in firing frequency in response to depolarizing current injection. In the six cell classes examined, no changes were observed in the resting membrane potential, input resistance, rheobase, spike amplitude, or spike duration after application of dopamine. The durations of action potentials broadened by application of tetraethylammonium in motoneurons and of calcium action potentials in dorsal cells and giant interneurons were decreased after bath application of 10 μM dopamine. The durations of tetrodotoxin-resistant, N-methyl-d-aspartate-induced membrane potential oscillations in lamprey spinal motoneurons were increased after bath application of 1–100 μM dopamine, due perhaps to reduced calcium entry and thus reduced Ca2+-dependent K+ current responsible for the repolarization of the membrane potential during each oscillation. Polysynaptic inhibitory postsynaptic potentials (IPSPs) elicited in lamprey spinal motoneurons by stimulation of the contralateral half of the spinal cord were reduced by bath application of 10 μM dopamine. Polysynaptic excitatory postsynaptic potentials were not reduced by dopamine. Monosynaptic IPSPs in motoneurons elicited by stimulation of single contralateral inhibitory CC interneurons and single ipsilateral axons were reduced by bath application of dopamine (10 μM). Monosynaptic IPSPs in CC interneurons elicited by stimulation of ipsilateral lateral interneurons, however, showed no change after application of dopamine. The lack of dopaminergic effect on the late AHP of the locomotor network neurons, lateral interneurons and CC interneurons, and the selective reduction of IPSPs from CC interneurons suggest that synaptic modulation may play an important role in dopaminergic modulation of cycle period during fictive swimming in the lamprey.

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)

Tachykinin-mediated modulation of sensory neurons, interneurons, and synaptic transmission in the lamprey spinal cord

1996 ◽  
Vol 76 (6) ◽  
pp. 4031-4039 ◽  
Author(s):  
D. Parker ◽  
S. Grillner
Keyword(s):  
Spinal Cord ◽  
Substance P ◽  
Synaptic Transmission ◽  
Dorsal Root ◽  
Input Resistance ◽  
Dorsal Column ◽  
Giant Interneurons ◽  
Potassium Conductances ◽  
Dorsal Cells ◽  
Measurable Change

1. Tachykinin-like immunoreactivity is found in the dorsal roots, dorsal horn, and dorsal column of the lamprey. The effect of tachykinins on sensory processing was examined by recording intracellularly from primary sensory dorsal cells and second-order spinobulbar giant interneurons. Modulation of synaptic transmission was examined by making paired recordings from dorsal cells and giant interneurons, or by eliciting compound depolarizations in the giant interneurons by stimulating the dorsal root or dorsal column. 2. Bath application of tachykinins depolarized the dorsal cells. This effect was mimicked by stimulation of the dorsal root, suggesting that dorsal root afferents may be a source of endogenous tachykinin input to the spinal cord. The depolarization was reduced by removal of sodium or calcium from the Ringer, or when potassium conductances were blocked, and was not associated with a measurable change in input resistance. Dorsal root stimulation also caused a depolarization in the dorsal cells, and this effect and that of bath-applied substance P, was blocked by the tachykinin antagonist spantide. 3. The tachykinin substance P could reduce inward and outward rectification in the dorsal cells, the effect on outward rectification only being seen when potassium conductances were blocked by tetraethylammonium (TEA). 4. Substance P increased the excitability of the dorsal cells and giant interneurons, shown by the increased spiking in response to depolarizing current pulses. The increased excitability was blocked by the tachykinin antagonist spantide. 5. Substance P modulated the dorsal cell action potential, by increasing the spike duration and reducing the amplitude of the afterhyperpolarization. The spike amplitude was not consistently affected. 6. Stimulation of the dorsal column resulted in either depolarizing or hyperpolarizing potentials in the giant interneurons. The amplitude of the depolarization was increased by substance P, whereas the amplitude of the hyperpolarization was reduced. These effects occurred independently of a measurable change in postsynaptic input resistance, suggesting that the modulation occurred presynaptically. Paired recordings from dorsal cells and giant interneurons failed to reveal an effect of substance P on dorsal cell-evoked excitatory postsynaptic potentials (EPSPs), suggesting that the potentiation of the dorsal column-evoked depolarization was due to an effect on other axons in the dorsal column. Dorsal root-evoked potentials could also be increased in the presence of substance P, although this effect was less consistent than the effect on dorsal column stimulation. 7. These results suggest that tachykinins modulate sensory input to the lamprey spinal cord by increasing the excitability of primary afferents and second-order giant interneurons, and also by modulating synaptic transmission. Tachykinins may result in potentiation of local spinal reflexes and also modulation of descending reticulospinal inputs to the spinal locomotor network as a result of potentiation of spinobulbar inputs.

Activity of commissural interneurons in spinal cord of Xenopus embryos

1984 ◽  
Vol 51 (6) ◽  
pp. 1257-1267 ◽  
Author(s):  
S. R. Soffe ◽  
J. D. Clarke ◽  
A. Roberts
Keyword(s):  
Spinal Cord ◽  
Rhythmic Activity ◽  
Excitatory Input ◽  
Cycle Period ◽  
Fictive Locomotion ◽  
Anatomy And Physiology ◽  
Postsynaptic Potential ◽  
Natural Stimulation ◽  
Xenopus Laevis Embryos ◽  
Stimulation Of

Horseradish peroxidase- (HRP) filled microelectrodes have been used to examine the anatomy and physiology of "commissural interneurons," a morphologically defined class of spinal cord interneuron in Xenopus laevis embryos. Commissural interneurons have unipolar cell bodies in the dorsal half of the spinal cord. Their dendrites lie in the mid to ventral parts of the lateral tracts and their axons cross the cord ventrally, T branch, and ascend and descend on the opposite side of the cord. Recordings were made from animals immobilized in tubocurarine and responding to natural stimulation with three patterns of fictive motor activity. During episodes of fictive swimming, commissural interneurons are phasically excited to fire 1 spike/cycle in phase with motor discharge on the same side and receive a midcycle inhibitory postsynaptic potential (IPSP) in phase with motor discharge on the opposite side. Rhythmic activity is superimposed on a background depolarization. During periods of synchrony, phasic excitatory input doubles in frequency so that cells fire with half the swimming cycle period. The background depolarization is generally stronger than during swimming. During periods of fictive struggling, evoked by electrical stimulation of the skin, commissural interneurons fire a burst of spikes per cycle, cells being relatively hyperpolarized when motoneurons on the opposite side are active. In response to ipsilateral skin stimulation, some cells receive an IPSP at a latency of 12-20 ms. This precedes the onset of fictive locomotion. We discuss how anatomy and activity of commissural interneurons is suitable for a reciprocal inhibitory role.

Dorsal Spinocerebellar Tract Neurons Are Not Subjected to Postsynaptic Inhibition During Carbachol-Induced Motor Inhibition

1997 ◽  
Vol 78 (1) ◽  
pp. 137-144 ◽  
Author(s):  
Ming-Chu Xi ◽  
Jack Yamuy ◽  
Rong-Huan Liu ◽  
Francisco R. Morales ◽  
Michael H. Chase
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Synaptic Activity ◽  
Motor Inhibition ◽  
Postsynaptic Inhibition ◽  
Postsynaptic Potentials ◽  
Group I ◽  
The Mean ◽  
Spinocerebellar Tract ◽  
Clarke's Column

Xi, Ming-Chu, Jack Yamuy, Rong-Huan Liu, Francisco R. Morales, and Michael H. Chase. Dorsal spinocerebellar tract neurons are not subjected to postsynaptic inhibition during carbachol-induced motor inhibition. J. Neurophysiol. 78: 137–144, 1997. Dorsal spinocerebellar tract (DSCT) neurons in Clarke's column in the lumbar spinal cord of cats anesthetized with α-chloralose were recorded intracellularly. The membrane potential activity and electrophysiological properties of these neurons were examined before and during the state of active-sleep-like motor inhibition induced by the injection of carbachol into the nucleus pontis oralis. The synaptic activity of DSCT neurons during carbachol-induced motor inhibition did not change compared with that during control conditions. In particular, there was an absence of inhibitory postsynaptic potentials (IPSPs) in high-gain recordings from DSCT neurons and the resting membrane potential of DSCT neurons was not significantly hyperpolarized during carbachol-induced motor inhibition. The mean amplitude of both monosynaptic excitatory postsynaptic potentials and disynaptic IPSPs evoked in DSCT neurons following stimulation of group I muscle afferents after the injection of carbachol was similar to that evoked before the injection of carbachol. There were no significant changes in the mean input resistance and membrane time constant of DSCT neurons during carbachol-induced motor inhibition. We conclude that, in contrast to lumbar motoneurons, DSCT neurons in Clarke's column are not postsynaptically inhibited during carbachol-induced motor inhibition. Therefore the population of spinal cord Ib interneurons that inhibit both DSCT neurons and lumbar motoneurons is not likely to be the interneurons that are responsible for the postsynaptic inhibition of motoneurons that occurs during carbachol-induced motor inhibition. The present findings also indicate that transmission through the DSCT is not modulated by postsynaptic inhibition at the level of DSCT neurons during carbachol-induced motor inhibition.

scholarly journals Intracellular QX-314 Causes Depression of Membrane Potential Oscillations in Lamprey Spinal Neurons During Fictive Locomotion

2002 ◽  
Vol 87 (6) ◽  
pp. 2676-2683 ◽  
Author(s):  
Guo-Yuan Hu ◽  
Zoltán Biró ◽  
Russell H. Hill ◽  
Sten Grillner
Keyword(s):  
Spinal Cord ◽  
Membrane Potential ◽  
Dendritic Tree ◽  
Cell Voltage ◽  
Fictive Locomotion ◽  
Spinal Neurons ◽  
Potential Oscillations ◽  
Short Pulses ◽  
Voltage Dependent ◽  
Membrane Potential Oscillations

Spinal neurons undergo large cyclic membrane potential oscillations during fictive locomotion in lamprey. It was investigated whether these oscillations were due only to synaptically driven excitatory and inhibitory potentials or if voltage-dependent inward conductances also contribute to the depolarizing phase by using N-(2,6-dimethylphenyl carbamoylmethyl)triethylammonium bromide (QX-314) administered intracellularly during fictive locomotion. QX-314 intracellularly blocks inactivating and persistent Na+ channels, and in some neurons, effects on certain other types of channels have been reported. To detail the effects of QX-314 on Na+ and Ca2+ channels, we used dissociated lamprey neurons recorded under whole cell voltage clamp. At low intracellular concentrations of QX-314 (0.2 mM), inactivating Na+ channels were blocked and no effects were exerted on Ca2+ channels (also at 0.5 mM). At 10 mM QX-314, there was, however a marked reduction of I Ca. In the isolated spinal cord of the lamprey, fictive locomotion was induced by superfusing the spinal cord with Ringer's solution containing N-methyl-d-aspartate (NMDA), while recording the locomotor activity from the ventral roots. Simultaneously, identified spinal neurons were recorded intracellularly, while infusing QX-314 from the microelectrode. Patch electrodes cannot be used in the intact spinal cord, and therefore “sharp” electrodes were used. The amplitude of the oscillations was consistently reduced by 20–25% in motoneurons ( P < 0.05) and unidentified spinal neurons ( P < 0.005). The onset of the effect started a few minutes after impalement and reached a stable level within 30 min. These effects thus show that QX-314 causes a reduction in the amplitude of membrane potential oscillations during fictive locomotion. We also investigated whether QX-314 could affect glutamate currents by applying short pulses of glutamate from an extracellular pipette. No changes were observed. We also found no evidence for a persistent Na+ current in dissociated neurons, but these cells have a much-reduced dendritic tree. The results indicate that there is an inward conductance, which is sensitive to QX-314, during membrane potential oscillations that “boosts” the synaptic drive during fictive locomotion. Taken together, the results suggest that inactivating Na+ channels contribute to this inward conductance although persistent Na+channels, if present on dendrites, could possibly also contribute to shaping the membrane potential oscillations.

scholarly journals Spinobulbar Neurons in Lamprey: Cellular Properties and Synaptic Interactions

2006 ◽  
Vol 96 (4) ◽  
pp. 2042-2055 ◽  
Author(s):  
James F. Einum ◽  
James T. Buchanan
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Feedback Inhibition ◽  
Inhibitory Synapses ◽  
Medium Size ◽  
Spinal Neurons ◽  
Lower Vertebrate ◽  
Dorsal Cells ◽  
The Brain

An in vitro preparation of the nervous system of the lamprey, a lower vertebrate, was used to characterize the properties of spinal neurons with axons projecting to the brain stem [i.e., spinobulbar (SB) neurons)]. To identify SB neurons, extracellular electrodes on each side of the spinal cord near the obex recorded the axonal spikes of neurons impaled with sharp intracellular microelectrodes in the rostral spinal cord. The ascending spinal neurons ( n = 144) included those with ipsilateral (iSB) (63/144), contralateral (cSB) (77/144), or bilateral (bSB) (4/144) axonal projections to the brain stem. Intracellular injection of biocytin revealed that the SB neurons had small- to medium-size somata and most had dendrites confined to the ipsilateral side of the cord, although about half of the cSB neurons also had contralateral dendrites. Most SB neurons had multiple axonal branches including descending axons. Electrophysiologically, the SB neurons were similar to other lamprey spinal neurons, firing spikes throughout long depolarizing pulses with some spike-frequency adaptation. Paired intracellular recordings between SB and reticulospinal (RS) neurons revealed that SB neurons made either excitatory or inhibitory synapses on RS neurons and the SB neurons received excitatory input from RS neurons. Mutual excitation and feedback inhibition between pairs of RS and SB neurons were observed. The SB neurons also received excitatory inputs from primary mechanosensory neurons (dorsal cells), and these same SB neurons were rhythmically active during fictive swimming, indicating that SB neurons convey both sensory and locomotor network information to the brain stem.

Influence of input from the Forewing Stretch Receptors on Motoneurones in Flying Locusts

1990 ◽  
Vol 151 (1) ◽  
pp. 317-340 ◽  
Author(s):  
K. G. PEARSON ◽  
J. M. RAMIREZ
Keyword(s):  
Membrane Potential ◽  
Excitatory Input ◽  
Cycle Period ◽  
Strongly Correlated ◽  
Intracellular Recordings ◽  
Wingbeat Frequency ◽  
Potential Oscillations ◽  
Stretch Receptors ◽  
Membrane Potential Oscillations ◽  
Stimulation Of

1. Previous studies on the forewing stretch receptors (FSRs) of locusts have suggested that feedback from these receptors during flight contributes to the excitation of depressor motoneurones and reduces the duration of depolarizations in elevator motoneurones. We have investigated these proposals by measuring the timing of FSR activity relative to depressor activity and by examining the effects of stimulating the FSRs on the membrane potential oscillations in flight motoneurones. 2. Activity in the FSRs was recorded in tethered intact animals flying in a windstream and in preparations that allowed intracellular recordings from motoneurones during flight activity. The timing of FSR activity was similar in both preparations. In most animals we observed that at normal wingbeat frequencies (about 20 Hz) the activity in the FSRs commenced after the onset of activity in the wing depressor muscles. As wingbeat frequency declined there was a progressive advance of FSR activity relative to depressor activity. Most of the spikes in each burst of FSR activity occurred during the time that the membrane potential in depressor motoneurones was repolarizing. 3. Electrical stimulation of the FSRs timed to follow the onset of depressor activity slowed the rate of repolarization, decreased the peak hyperpolarization and increased the rate of the following depolarization in depressor motoneurones. In elevator motoneurones, the same pattern of FSR stimulation produced an additional excitatory input during the depolarization phase and, at low wingbeat frequencies, reduced the duration of the peak depolarizations. The reduction in the duration of the peak depolarization in elevator motoneurones was not strongly correlated to the reduction in cycle period. 4. We propose that the primary reason why input from the FSRs increases wingbeat frequency is because this input reduces the degree of hyperpolarization in depressor neurones and thus promotes an earlier onset of the next depolarization in these neurones.

Spinal Fos labeling and penile erection elicited by stimulation of dorsal nerve of the rat penis

1997 ◽  
Vol 272 (5) ◽  
pp. R1425-R1431 ◽  
Author(s):  
O. Rampin ◽  
S. Gougis ◽  
F. Giuliano ◽  
J. P. Rousseau
Keyword(s):  
Spinal Cord ◽  
Inhibitory Control ◽  
Penile Erection ◽  
Sensory Information ◽  
Immunocytochemical Staining ◽  
Spinal Neurons ◽  
Afferent Limb ◽  
Sacral Parasympathetic Nucleus ◽  
Dorsal Nerve ◽  
Stimulation Of

Penile afferents present in the dorsal nerve of the penis (DNP) convey sensory information from the penis to the spinal cord and represent the afferent limb of reflexive erections. Immunocytochemical staining of Fos was used to identify spinal neurons that receive excitatory inputs from the DNP in anesthetized rats. Intracavernous pressure (ICP) was recorded as an index of erection. Dissection as well as stimulation of the DNP elicited a comparable increase in Fos staining. Labeling was present in the dorsal horn, the dorsal gray commissure, and the sacral parasympathetic nucleus, supporting the hypothesis of direct or indirect afferent projection from the penis and penile sheath in these areas. No change in ICP was observed in these rats. Stimulation of the DNP elicited both increased Fos labeling and ICP after spinalization, demonstrating the presence of a supraspinal inhibitory control exerted on the polysynaptic intraspinal circuitry responsible for reflexive penile erection.

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.

Sign in / Sign up

Export Citation Format

Share Document