scholarly journals Contribution of Ca 2+ ‐dependent conductances to membrane potential fluctuations of medullary respiratory neurons of newborn rats in vitro

2003 ◽  
Vol 552 (3) ◽  
pp. 727-741 ◽  
Author(s):  
Hiroshi Onimaru ◽  
Klaus Ballanyi ◽  
Ikuo Homma
Keyword(s):  
Membrane Potential ◽  
Respiratory Neurons ◽  
Newborn Rats ◽  
Potential Fluctuations ◽  
Medullary Respiratory Neurons ◽  
Membrane Potential Fluctuations

Inputs to intercostal motoneurons from ventrolateral medullary respiratory neurons in the cat

1987 ◽  
Vol 57 (6) ◽  
pp. 1837-1853 ◽  
Author(s):  
E. G. Merrill ◽  
J. Lipski
Keyword(s):  
Membrane Potential ◽  
Respiratory Neurons ◽  
Respiratory Drive ◽  
Thoracic Spinal Cord ◽  
Medullary Respiratory Neurons ◽  
Thoracic Spinal ◽  
Synaptic Noise ◽  
Series Of Experiments ◽  
Intercostal Nerves ◽  
Descending Projections

The investigation examined the synaptic input from medullary respiratory neurons in the nucleus retroambigualis (NRA) to external (EIM) and internal (IIM) intercostal motoneurons. Antidromic mapping revealed that 112/117 (96%) tested NRA units had axons descending into thoracic spinal cord with extensive arborizations at many thoracic segments, mainly contralaterally. The conduction velocities ranged from 10 to 105 m X s-1. The descending projections did not appear to be somatotopically arranged. Cross-correlation of the spike trains of NRA inspiratory units with the discharge of external intercostal nerves (performed usually with 4 contralateral nerves) showed significant narrow peaks only in 5 out of 40 averages. Of the 25 trigger units tested for the thoracic projection in this series of experiments, 24 were antidromically activated. Intracellular recordings were made from 52 IIMs [mean membrane potential 65.3 mV, central respiratory drive potentials (CRDPs) greater than 1 mV present in 23/52] and 53 EIM (mean membrane potential 54.3 mV, CRDPs in 31/53). During the depolarizing phase of the CRDPs, synaptic noise with frequent and apparently unitary EPSPs with amplitudes in excess of 1 mV was observed. Spike-triggered averages of synaptic noise were computed for 153 pairings between 137 NRA neurons and 105 contralateral intercostal motoneurons. Only four PSPs were revealed: two monosynaptic EPSPs between expiratory NRA units and IIMs and two probably disynaptic EPSPs between inspiratory NRA units and EIMs. When advancing the microelectrode down to the motoneuron pools, frequent recordings were made from interneurons with spontaneous respiratory discharge (inspiratory or expiratory) located dorsal and medial to the motor nuclei. The interneurons could be excited following stimulation of segmental afferents. It is concluded that monosynaptic connections between respiratory NRA neurons and intercostal motoneurons are rare (connectivity no more than approximately 4%). Segmental interneurons, interposed between the majority of descending respiratory axons and intercostal motoneurons, are likely to produce large unitary EPSPs and, thus, short-term synchronization in the discharge of intercostal motoneurons as observed by others.

Spontaneous Subthreshold Membrane Potential Fluctuations and Action Potential Variability of Rat Corticostriatal and Striatal Neurons In Vivo

1997 ◽  
Vol 77 (4) ◽  
pp. 1697-1715 ◽  
Author(s):  
Edward A. Stern ◽  
Anthony E. Kincaid ◽  
Charles J. Wilson
Keyword(s):  
Membrane Potential ◽  
Synaptic Input ◽  
High Frequency ◽  
Action Potentials ◽  
State Transitions ◽  
Striatal Neurons ◽  
Interspike Intervals ◽  
Potential Fluctuations ◽  
Membrane Potential Fluctuations

Stern, Edward A., Anthony E. Kincaid, and Charles J. Wilson. Spontaneous subthreshold membrane potential fluctuations and action potential variability of rat corticostriatal and striatal neurons in vivo. J. Neurophysiol. 77: 1697–1715, 1997. We measured the timing of spontaneous membrane potential fluctuations and action potentials of medial and lateral agranular corticostriatal and striatal neurons with the use of in vivo intracellular recordings in urethan-anesthetized rats. All neurons showed spontaneous subthreshold membrane potential shifts from 7 to 32 mV in amplitude, fluctuating between a hyperpolarized down state and depolarized up state. Action potentials arose only during the up state. The membrane potential state transitions showed a weak periodicity with a peak frequency near 1 Hz. The peak of the frequency spectra was broad in all neurons, indicating that the membrane potential fluctuations were not dominated by a single periodic function. At frequencies >1 Hz, the log of magnitude decreased linearly with the log of frequency in all neurons. No serial dependence was found for up and down state durations, or for the time between successive up or down state transitions, showing that the up and down state transitions are not due to superimposition of noisy inputs onto a single frequency. Monte Carlo simulations of stochastic synaptic inputs to a uniform finite cylinder showed that the Fourier spectra obtained for corticostriatal and striatal neurons are inconsistent with a Poisson-like synaptic input, demonstrating that the up state is not due to an increase in the strength of an unpatterned synaptic input. Frequency components arising from state transitions were separated from those arising from the smaller membrane potential fluctuations within each state. A larger proportion of the total signal was represented by the fluctuations within states, especially in the up state, than was predicted by the simulations. The individual state spectra did not correspond to those of random synaptic inputs, but reproduced the spectra of the up and down state transitions. This suggests that the process causing the state transitions and the process responsible for synaptic input may be the same. A high-frequency periodic component in the up states was found in the majority of the corticostriatal cells in the sample. The average size of the component was not different between neurons injected with QX-314 and control neurons. The high-frequency component was not seen in any of our sample of striatal cells. Corticostriatal and striatal neurons' coefficients of variation of interspike intervals ranged from 1.0 to 1.9. When interspike intervals including a down state were subtracted from the calculation, the coefficient of variation ranged from 0.4 to 1.1, indicating that a substantial proportion of spike interval variance was due to the subthreshold membrane potential fluctuations.

Membrane potential fluctuations produced by glutamate in nerve cells of the squid

1975 ◽  
Vol 191 (1105) ◽  
pp. 561-565 ◽  
Keyword(s):  
Membrane Potential ◽  
Neuromuscular Junctions ◽  
Noise Analysis ◽  
Postsynaptic Membrane ◽  
Nerve Cells ◽  
Voltage Fluctuations ◽  
Potential Fluctuations ◽  
Synaptic Inputs ◽  
Small Voltage ◽  
Membrane Potential Fluctuations

Glutamate-induced potential changes have been recorded with intracellular electrodes in nerve cells of the squid. The responses are accompanied by small voltage fluctuations which resemble postsynaptic ‘membrane noise’ observed at neuromuscular junctions. Certain limitations are discussed in extending the noise analysis to neurons with multiple synaptic inputs.

Action of barium and potassium ions on membrane potential fluctuations of rat papillary cardiomyocytes

1987 ◽  
Vol 103 (3) ◽  
pp. 283-286
Author(s):  
S. I. Zakharov ◽  
K. Yu. Bogdanov ◽  
A. V. Zaitsev ◽  
L. V. Rozenshtraukh
Keyword(s):  
Membrane Potential ◽  
Potassium Ions ◽  
Potential Fluctuations ◽  
Membrane Potential Fluctuations

Different Effects of Gabaergic Anticonvulsants on 4-Aminopyridine-Induced Spontaneous Gabaergic Hyperpolarizations of Hippocampal Pyramidal Cells—Implication for their Potency in Migraine Therapy

Cephalalgia ◽  
2000 ◽  
Vol 20 (6) ◽  
pp. 533-537 ◽  
Author(s):  
T Leniger ◽  
M Wiemann ◽  
D Bingmann ◽  
A Hufnagel ◽  
U Bonnet
Keyword(s):  
Clinical Studies ◽  
Pyramidal Cells ◽  
Intracellular Recordings ◽  
Migraine Therapy ◽  
Potential Fluctuations ◽  
Acting Agent ◽  
Fast Acting ◽  
Membrane Potential Fluctuations ◽  
Hippocampal Pyramidal Cells

Clinical studies indicate anti-migraneous efficacy of the probably GABAergic anti-convulsants valproate and gabapentin. For the GABAergic anticonvulsants vigabatrin and tiagabine, studies about antimigraneous efficacy are missing. The aim of this study was to test the GABAergic potency of these drugs in vitro before further clinical studies. Intracellular recordings were obtained from hippocampal pyramidal cells. Spontaneous GABAergic hyperpolarizations (SGH) elicited by 75 μ m 4-aminopyridine were used to test the effect of these drugs on GABA-dependent potentials. Tiagabine (0.1 m m) prolonged the duration of SGH. Furthermore, monophasic SGH turned over into triphasic typical GABAergic membrane potential fluctuations within 20 min. In contrast, valproate, gabapentin, and vigabatrin failed to affect SGH up to 60 min of application. The reason for the fast action of tiagabine on SGH may be caused by a faster increase of synaptic GABA levels compared with other drugs. As migraine therapy benefits from an augmentation of GABA activity, we recommend clinical studies of tiagabine as a fast-acting agent in migraine attacks.

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