The effect of carbon dioxide on the membrane potential of medullary respiratory neurons

1974 ◽  
Vol 75 (2) ◽  
pp. 345-349 ◽  
Author(s):  
R.A. Mitchell ◽  
D.A. Herbert
Keyword(s):  
Carbon Dioxide ◽  
Membrane Potential ◽  
Respiratory Neurons ◽  
Medullary Respiratory Neurons

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.

Accommodative reactions of medullary respiratory neurons of the cat

1975 ◽  
Vol 38 (5) ◽  
pp. 1172-1180 ◽  
Author(s):  
D. W. Richter ◽  
F. Heyde
Keyword(s):  
Membrane Potential ◽  
Synaptic Input ◽  
Early Period ◽  
Rhythmic Activity ◽  
Respiratory Neurons ◽  
Current Frequency ◽  
Burst Discharge ◽  
Current Pulses ◽  
Medullary Respiratory Neurons ◽  
Frequency Relationship

In most of the bulbospinal respiratory neurons, threshold depolarization increased during the early period of their spontaneous burst discharge but decreased again at the end of a burst. In some vagal respiratory neurons, however, threshold depolarization increased steadily until the very end of their discharge period. These changes generally were accompanied by changes in the rate of depol1rization of the spikes, the amplitude of their overshoot, and their discharge frequency. For a given synaptic input, as indicated by the constancy of the interspike membrane potential trajectories, threshold depolarization of bulbospinal neurons remained constant or even decreased. Only in some vagal neurons was an increase in threshold deplarization observed under these conditions. With the exception of some vagal neurons, most of the respiratory neurons did not show a pronounced accommodative behavior when stimulated with linear rising currents. When stimulating with current pulses, all neurons discharged repetitively with only slight adaptation, which was already complete by the first few spike intervals. The current-frequency relationship was linear and revealed a primary and secondary range. The results support neither accommodation nor adaptation as important mechanisms in the genesis of the rhythmic activity of respiratory neurons.

Changes in antidromic latencies of medullary respiratory neurons in hypercapnia and hypoxia

1985 ◽  
Vol 59 (4) ◽  
pp. 1208-1213 ◽  
Author(s):  
A. L. Bianchi ◽  
W. M. St John
Keyword(s):  
Membrane Potential ◽  
Neuronal Activity ◽  
Membrane Potentials ◽  
Respiratory Neurons ◽  
Strongly Correlated ◽  
Antidromic Activation ◽  
Axonal Projections ◽  
Medullary Respiratory Neurons ◽  
Spontaneous Neuronal Activity ◽  
The Difference

We evaluated mechanisms underlying changes in discharge frequencies of medullary respiratory neurons. This evaluation was made by determining variations in antidromic latencies; these variations reflect changes in membrane potentials. In decerebrate, vagotomized, paralyzed, and ventilated cats, activities of the phrenic nerve and single respiratory neurons were monitored in hyperoxic normocapnia, hyperoxic hypercapnia, and/or normocapnic hypoxia. Axonal projections were defined as bulbospinal or laryngeal by antidromic activation. At normocapnic hyperoxia, antidromic latencies fell to minima during periods of spontaneous neuronal activity, with maxima occurring between neuronal bursts. In hypercapnia or hypoxia, these minima were not altered, whereas maximum latencies typically rose for neurons whose discharge frequencies increased. However, the increased frequencies most strongly correlated with increases in the difference between maximum and minimum latencies. No such correlation was evident for neurons whose discharge frequencies declined. We conclude that the overall change of membrane potential primarily defines neuronal discharge frequencies. Changes in membrane potentials induced by peripheral and central chemoreceptor afferents and by direct actions of hypercapnia and hypoxia are discussed.

scholarly journals Excitation of Medullary Respiratory Neurons in REM Sleep

SLEEP ◽  
2005 ◽  
Vol 28 (7) ◽  
pp. 801-807 ◽  
Author(s):  
John M. Orem ◽  
Andrew T. Lovering ◽  
Edward H. Vidruk
Keyword(s):  
Rem Sleep ◽  
Respiratory Neurons ◽  
Medullary Respiratory Neurons

Functional associations among simultaneously monitored lateral medullary respiratory neurons in the cat. II. Evidence for inhibitory actions of expiratory neurons

1987 ◽  
Vol 57 (4) ◽  
pp. 1101-1117 ◽  
Author(s):  
B. G. Lindsey ◽  
L. S. Segers ◽  
R. Shannon
Keyword(s):  
Discharge Rate ◽  
Respiratory Neurons ◽  
Short Time Scale ◽  
Axonal Projections ◽  
Medullary Respiratory Neurons ◽  
Antidromic Stimulation ◽  
Expiratory Neurons ◽  
Short Time ◽  
And Control ◽  
The Brain

Arrays of extracellular electrodes were used to monitor simultaneously several (2-8) respiratory neurons in the lateral medulla of anesthetized, paralyzed, bilaterally vagotomized, artificially ventilated cats. Efferent phrenic nerve activity was also recorded. The average discharge rate as a function of time in the respiratory cycle was determined for each neuron. Most cells were tested for spinal or vagal axonal projections using antidromic stimulation methods. Cross-correlational methods were used to analyze spike trains of 480 cell pairs. Each pair included at least one neuron most active during the expiratory phase. All simultaneously recorded neurons were located in the same side of the brain stem. Twenty-six percent (33/129) of the expiratory (E) neuron pairs exhibited short time scale correlations indicative of paucisynaptic interactions or shared inputs, whereas 8% (27/351) of the pairs consisting of an E neuron and an inspiratory (I) cell were similarly correlated. Evidence for several inhibitory actions of E neurons was found: 1) inhibition of I neurons by E neurons with both decrementing (DEC) and augmenting (AUG) firing patterns; 2) inhibition of E-DEC and E-AUG neurons by E-DEC cells; 3) inhibition of E-DEC and E-AUG neurons by E-AUG neurons; and 4) inhibition of E-DEC neurons by tonic I-E phase-spanning cells. Because several cells were recorded simultaneously, direct evidence for concurrent parallel and serial inhibitory processes was also obtained. The results suggest and support several hypotheses for mechanisms that may help to generate and control the pattern and coordination of respiratory motoneuron activities.

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