Discharge patterns of phrenic motoneurons during fictive coughing and vomiting in decerebrate cats

1992 ◽  
Vol 73 (4) ◽  
pp. 1626-1636 ◽  
Author(s):  
S. Milano ◽  
L. Grelot ◽  
A. L. Bianchi ◽  
S. Iscoe
Keyword(s):  
Interspike Interval ◽  
Discharge Frequency ◽  
Motor Axons ◽  
Antidromic Activation ◽  
Phrenic Motoneurons ◽  
Active Motor ◽  
Recruitment Order ◽  
Discharge Patterns ◽  
Decerebrate Cats

In decerebrate, paralyzed, and ventilated cats, we recorded the activity of 100 spontaneously active phrenic motor axons during the increased phrenic discharges characteristic of fictive vomiting (FV) and coughing (FC). During control respiratory cycles, approximately one-half the neurons were recruited in the first decile of inspiration; recruitment continued throughout inspiration. During FV, the duration of phrenic discharge was halved; 20 of 26 motoneurons studied were recruited in the first decile of the burst. During FC, recruitment times did not change compared with control, although the duration of the phrenic burst doubled. Discharge frequencies increased and recruitment order of phrenic motoneurons was virtually unaffected during FC and FV. Limited recruitment of previously inactive neurons in the filaments from which we recorded was found during FV and FC. During FV, 1 previously inactive motoneuron was recruited in 16 filaments containing 25 spontaneously active motor axons. During FC, 3 new motoneurons were recruited in addition to the 64 already active in 35 filaments. Recruitment during FV and FC was absent even when recording from filaments known, on the basis of antidromic activation, to contain inactive motor axons. During FV, 10 of 26 motoneurons began their discharges with doublets (interspike interval < 10 ms); doublets occurred in only 4 of 67 motoneurons during FC. Already active phrenic motoneurons contributed to the intense phrenic activity associated with both respiratory (coughing) and nonrespiratory (vomiting) behavior by increases in discharge frequency, earlier recruitment, and doublets; the contribution of previously quiescent motoneurons remains uncertain.

Comparison of phrenic motoneuron responses to hypercapnia and isocapnic hypoxia

1979 ◽  
Vol 46 (6) ◽  
pp. 1096-1102 ◽  
Author(s):  
W. M. St John ◽  
D. Bartlett
Keyword(s):  
Unit Activity ◽  
Phrenic Nerve ◽  
Interspike Interval ◽  
Activity Patterns ◽  
Nerve Fibers ◽  
Respiratory Cycle ◽  
Efferent Activity ◽  
Phrenic Motoneurons ◽  
Phrenic Motoneuron ◽  
Decerebrate Cats

This study was undertaken to compare phrenic motoneuron responses to hypercapnia and isocapnic hypoxia. Efferent activity of single phrenic nerve fibers was recorded with that of the contralateral phrenic nerve in decerebrate cats which were vagotomized, paralyzed, and artificially ventilated. At normocapnia in hyperoxia, single phrenic fibers were distributed into approximately equal “early” and “late” populations according to their onset of activity relative to the period of the phrenic burst. Elevations of PACO2 or diminutions of PAO2 resulted in progressive increases in the number of spikes per respiratory cycle and decreases in the modal interspike interval for both early and late units. Moreover, either stimulus caused an onset of late unit activity at progressively earlier portions of inspiration. At equivalent levels of peak integrated phrenic discharge achieved at normocapnia or hypercapnia as compared to normoxia or hypoxia, there were no differences in activity patterns for either early or late units. It is concluded that hypoxia-induced alterations in the activity of single phrenic motoneurons are identical to those changes resulting from hypercapnia.

Membrane potential changes of phrenic motoneurons during fictive vomiting, coughing, and swallowing in the decerebrate cat

1992 ◽  
Vol 68 (6) ◽  
pp. 2110-2119 ◽  
Author(s):  
L. Grelot ◽  
S. Milano ◽  
F. Portillo ◽  
A. D. Miller ◽  
A. L. Bianchi
Keyword(s):  
Membrane Potential ◽  
Motor Nerve ◽  
Vagal Afferents ◽  
Antidromic Activation ◽  
Decerebrate Cat ◽  
Phrenic Motoneurons ◽  
Synaptic Noise ◽  
Motor Nerves ◽  
Phrenic Motoneuron ◽  
Discharge Patterns

1. The patterns of membrane potential changes of phrenic motoneurons were compared during fictive vomiting, fictive coughing, and fictive swallowing in decerebrate, paralyzed cats. These fictive behaviors were identified by motor nerve discharge patterns similar to those recorded from the muscles of nonparalyzed animals. Phrenic motoneurons (n = 54) were identified by antidromic activation from the thoracic phrenic nerve. Intracellular recordings were obtained from 27 motoneurons during fictive vomiting, 40 during fictive coughing, and 27 during fictive swallowing. Sixteen motoneurons were recorded during both fictive coughing and fictive swallowing, eight during both fictive coughing and fictive vomiting, and two during both fictive vomiting and fictive swallowing. Seven motoneurons were studied during all three behaviors. 2. Fictive vomiting, typically evoked by electrical stimulation of abdominal vagal afferents, was characterized by a series of bursts of coactivation of phrenic and abdominal motor nerves, culminating in an expulsion phase in which abdominal discharge was prolonged both with respect to phrenic discharge and to abdominal discharge during the preceding retching phase. During fictive vomiting, phrenic motoneurons depolarized abruptly, and the amplitude of depolarization was significantly greater than during control inspirations. They then repolarized slowly throughout the phrenic burst, rapidly repolarizing at the end of each phrenic burst during retching and reaching a level similar to that observed during expiration. During the expulsion phase, the pattern was initially the same. However, after the cessation of phrenic discharge, the membrane potential repolarized slowly until the end of the abdominal burst, exhibiting greater synaptic noise than during expiration. One phrenic motoneuron, presumably innervating the periesophageal region of the diaphragm, received a strong hyperpolarization just before the onset of the emetic episode and fired for shorter periods during fictive vomiting than did other phrenic motoneurons.(ABSTRACT TRUNCATED AT 250 WORDS)

Intrinsic features contributing to spike train patterning in proprioceptive cuneate neurons

1987 ◽  
Vol 57 (4) ◽  
pp. 962-976 ◽  
Author(s):  
D. J. Surmeier ◽  
A. L. Towe
Keyword(s):  
Computer Simulation ◽  
Spike Train ◽  
Spike Trains ◽  
Antidromic Activation ◽  
Synaptic Potentials ◽  
Class A ◽  
Class B ◽  
Class C ◽  
Discharge Patterns ◽  
Periodic Inputs

The intrinsic processes contributing to the three discharge patterns of proprioceptive cuneate neurons described by Surmeier and Towe were studied experimentally and with computer simulation. Examination of the alterations in excitability produced by antidromic activation suggested that a prolonged inhibition was a concomitant of discharge in proprioceptive cuneate neurons. Computer simulation was performed to test the possible roles of inhibitory hyperpolarizing processes in governing the observed discharge patterns. These simulations used two constant threshold models. The simplest model linearly integrated synaptic potentials until the spike threshold was reached. After the discharge, synaptic potentials that preceded the spike were ignored (i.e., the model was "reset"). The second model was similar to the first except that following a spike two hyperpolarizing processes were activated and preceding events continued to play a role in membrane potential. Simulation of class A spike trains that possessed positive correlations between nearby intervals was successful only with a resetting model. This suggested that class A neurons have fast, no-memory postspike conductance changes, which effectively shunt synaptic charge. Simulation of class B spike trains was possible with the nonresetting model. At least two periodic inputs, which evoked brief, relatively large EPSPs, were required. In addition, a prominent, fast, spike-dependent hyperpolarization and a small-amplitude, slow hyperpolarization were required. Simulation of class C spike trains was also possible with the nonresetting model. Several periodic inputs were required; one input had to evoke a slow suprathreshold EPSP. In contrast to class B simulations, class C spike train simulation required that a large-amplitude, slow hyperpolarization, as well as a brief hyperpolarization, following spike initiation. The results of class B and C simulations suggested that these two groups differed primarily in the amplitude of a slow, hyperpolarizing, postspike conductance. Some role may also be played by the time course of the driving EPSPs.

scholarly journals Phrenic Motoneuron Discharge Patterns During Hypoxia-Induced Short-Term Potentiation in Rats

2009 ◽  
Vol 102 (4) ◽  
pp. 2184-2193 ◽  
Author(s):  
Kun-Ze Lee ◽  
Paul J. Reier ◽  
David D. Fuller
Keyword(s):  
Phrenic Nerve ◽  
Cell Types ◽  
Progressive Increase ◽  
Short Term ◽  
Phrenic Motoneurons ◽  
Term Potentiation ◽  
Discharge Duration ◽  
Phrenic Motoneuron ◽  
Discharge Patterns ◽  
Increased Activity

Hypoxia-induced short-term potentiation (STP) of respiratory motor output is manifested by a progressive increase in activity after the acute hypoxic response and a gradual decrease in activity on termination of hypoxia. We hypothesized that STP would be differentially expressed between physiologically defined phrenic motoneurons (PhrMNs). Phrenic nerve “single fiber” recordings were used to characterize PhrMN discharge in anesthetized, vagotomized and ventilated rats. PhrMNs were classified as early (Early-I) or late inspiratory (Late-I) according to burst onset relative to the contralateral phrenic neurogram during normocapnic baseline conditions. During hypoxia (FIO2 = 0.12–0.14, 3 min), both Early-I and Late-I PhrMNs abruptly increased discharge frequency. Both cell types also showed a progressive increase in frequency over the remainder of hypoxia. However, Early-I PhrMNs showed reduced overall discharge duration and total spikes/breath during hypoxia, whereas Late-I PhrMNs maintained constant discharge duration and therefore increased the number of spikes/breath. A population of previously inactive (i.e., silent) PhrMNs was recruited 48 ± 8 s after hypoxia onset. These PhrMNs had a Late-I onset, and the majority (8/9) ceased bursting promptly on termination of hypoxia. In contrast, both Early-I and Late-I PhrMNs showed post-hypoxia STP as reflected by greater discharge frequencies and spikes/breath during the post-hypoxic period ( P < 0.01 vs. baseline). We conclude that the expression of phrenic STP during hypoxia reflects increased activity in previously active Early-I and Late-I PhrMNs and recruitment of silent PhrMNs. post-hypoxia STP primarily reflects persistent increases in the discharge of PhrMNs, which were active before hypoxia.

Recruitment order and dendritic morphology of rat phrenic motoneurons

1996 ◽  
Vol 366 (2) ◽  
pp. 231-243 ◽  
Author(s):  
Hidehisa Torikai ◽  
Fumiaki Hayashi ◽  
Koichi Tanaka ◽  
Tanemichi Chiba ◽  
Yasuichiro Fukuda ◽  
...  
Keyword(s):  
Dendritic Morphology ◽  
Phrenic Motoneurons ◽  
Recruitment Order

Influence of pulmonary inflations on discharge patterns of phrenic motoneurons

1987 ◽  
Vol 63 (4) ◽  
pp. 1421-1427 ◽  
Author(s):  
J. C. Hwang ◽  
W. M. St John ◽  
D. Bartlett
Keyword(s):  
Phrenic Nerve ◽  
Phrenic Motoneurons ◽  
Tracheal Pressure ◽  
Discharge Patterns ◽  
End Tidal ◽  
Late Stages

The purpose of this study was to assess the influence of pulmonary inflations on activities of single phrenic motoneurons. Studies were performed in decerebrate and paralyzed cats; activities of phrenic nerve and single phrenic motoneurons were recorded. Animals were ventilated with a servo-respirator which produced alterations in tracheal pressure in parallel with changes in integrated activity of the phrenic nerve. At end-tidal fractional concentrations of CO2 of 0.05, phrenic motoneurons were distributed into “early” and “late” populations, depending on time of onset of activity. During the late stages of neural inspiration, differences in levels of integrated activity of the phrenic nerve became evident between cycles with and without lung inflations. At a time approximating 90% of the inspiratory duration during inflations, integrated phrenic activity was higher for cycles with inflation. Concomitantly, with lung inflations, the discharge frequencies of early phrenic motoneurons were lower, and late motoneurons began to discharge sooner than when inflations were withheld. Similar results were obtained in hypercapnia. We conclude that reflexes activated by pulmonary inflations may produce augmentation, as well as inhibition of phrenic motoneuronal activities. Factors responsible for eliciting these reflex augmentations and inhibitions are discussed.

Characterization of respiratory-modulated activities of hypoglossal motoneurons

1983 ◽  
Vol 55 (3) ◽  
pp. 793-798 ◽  
Author(s):  
J. C. Hwang ◽  
D. Bartlett ◽  
W. M. St John
Keyword(s):  
Phrenic Nerve ◽  
Hypoglossal Nerve ◽  
Great Majority ◽  
Nerve Fibers ◽  
Hypoglossal Motoneurons ◽  
Phrenic Motoneurons ◽  
High Drive ◽  
Discharge Patterns ◽  
Neuronal Groups

In decerebrate, vagotomized, paralyzed, and ventilated cats, activities of the phrenic nerve and single hypoglossal nerve fibers were monitored. The great majority of hypoglossal neuronal activities were inspiratory (I), discharging during a period approximating that of phrenic. Many were not active at normocapnia but were recruited in hypercapnia or hypoxia. Once recruited, discharge frequencies, which rose quickly to near maximal levels in early to midinspiration, significantly increased with further augmentations of drive. Also, the onset of activities became progressively earlier, compared with phrenic discharge, in hypercapnia or hypoxia. Smaller numbers of hypoglossal fiber activities, having inspiratory-expiratory (I-E), expiratory (E), expiratory-inspiratory (E-I), or tonic discharge patterns, were also recorded. Activities of E, I-E, and those I fibers that became I-E in high drive may underlie the early burst of expiratory activity of the hypoglossal nerve. It is concluded that the firing and recruitment patterns of hypoglossal neurons differ from those of phrenic motoneurons. However, responses to chemoreceptor stimuli are similar among the two neuronal groups.

Pulmonary stretch receptor discharge patterns in eupnea, hypercapnia, and hypoxia

1982 ◽  
Vol 53 (2) ◽  
pp. 346-354 ◽  
Author(s):  
S. Iscoe
Keyword(s):  
Tidal Volume ◽  
Linear Equations ◽  
Discharge Frequency ◽  
Stretch Receptors ◽  
Pulmonary Stretch Receptors ◽  
Residual Capacity ◽  
Instantaneous Discharge ◽  
Discharge Patterns ◽  
Spontaneously Breathing ◽  
Pulmonary Stretch Receptor

The discharge properties of pulmonary stretch receptors (PSR) were studied in spontaneously breathing, pentobarbital sodium-anesthetized cats. During eupneic breathing, 105 of 116 PSR (both tonically and phasically active) were recruited in the first third of inspiration; none were recruited in the last third. Linear equations adequately expressed the relation between instantaneous discharge frequency and inspired volume in eupnea. During CO2 rebreathing, both tidal volume and peak PSR discharge frequency were inversely related to inspiratory duration. At fixed volumes less than 40 ml above functional residual capacity, instantaneous PSR discharge frequency either did not change or decreased with increases in flow. Above 40 ml, increases in discharge frequency accompanied increases in flow (0.033 spikes/s per ml/s). During progressive hypocapnic hypoxia, discharge frequency increased, on average, at all volumes with increases in flow (0.206 spikes/s per ml/s). During both conditions, as with eupnea, increases in frequency were linearly related to increments in tidal volume. Therefore, tidal volume alone can be used to estimate PSR feedback to the respiratory centers, provided that its instantaneous value is appropriately scaled to account for the different effects of CO2 and hypocapnic hypoxia on PSR discharge.

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