Brain stem genesis of automatic ventilatory patterns independent of spinal mechanisms

1981 ◽  
Vol 51 (1) ◽  
pp. 204-210 ◽  
Author(s):  
W. M. St John ◽  
D. Bartlett ◽  
K. V. Knuth ◽  
J. C. Hwang
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Phrenic Nerve ◽  
Spinal Transection ◽  
O2 Partial Pressure ◽  
Before And After ◽  
Inspiratory Activity ◽  
Discharge Patterns ◽  
End Tidal ◽  
Cervical Level

Efferent activities on the phrenic and recurrent laryngeal (RLN) nerves were monitored during eupnea, apneusis, and gasping in decerebrate, paralyzed, and ventilated cats before and after spinal cord transection at the first cervical level. The vagi were sectioned caudal to the RLN being studied and at the midcervical level contralaterally. Before spinal transection, the onset of RLN inspiratory activity preceded that of the phrenic nerve during eupnea and apneusis; in gasping, phrenic activity began before the RLN. These results were the same in normocapnia, hypercapnia, and hypoxia. After spinal transection, no phasic phrenic activity was observed at normoxia or hyperoxia, whereas the RLN exhibited discharge patterns similar to those before transection. Upon end-tidal O2 partial pressure diminutions below 50 Torr, one or more "burst" of phrenic activity were recorded. These bursts were not synchronized with the phasic RLN discharge. It is concluded that automatic ventilatory activity may be generated by inherent brain stem mechanisms. These results further imply the processes underlying gasping neurogenesis may differ fundamentally from those of eupnea or apneusis.

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.

Neurogenesis, control, and functional significance of gasping

1990 ◽  
Vol 68 (4) ◽  
pp. 1305-1315 ◽  
Author(s):  
W. M. St John
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Neural Circuits ◽  
Pattern Generator ◽  
Backup System ◽  
Neuronal Mechanisms ◽  
Inspiratory Activity ◽  
Respiratory Rhythms ◽  
Similar Elements ◽  
Stem Segments

Gasps are frequently the first and last breaths of life. Gasping, which is generated by intrinsic medullary mechanisms, differs fundamentally from other automatic ventilatory patterns. A region of the lateral tegmental field of the medulla is critical for the neurogenesis of the gasp but has no role in eupnea. Neuronal mechanisms in separate brain stem regions may be responsible for the neurogenesis of different ventilatory patterns. This hypothesis is supported by the recording of independent respiratory rhythms simultaneously from isolated brain stem segments. Data from fetal and neonatal animals also support gasping and eupnea being generated by separate mechanisms. Gasping may represent the output of a simple but rugged pattern generator that functions as a backup system until the control system for eupnea is developed. Pacemaker elements are hypothesized as underlying the onset of inspiratory activity in gasping. Similar elements, in a different brain stem region, may be responsible for the onset of the eupneic inspiration with neural circuits involving the pons, the medulla, and the spinal cord serving to shape efferent respiratory-modulated neural discharges.

scholarly journals Midcervical neuronal discharge patterns during and following hypoxia

2015 ◽  
Vol 113 (7) ◽  
pp. 2091-2101 ◽  
Author(s):  
M. S. Sandhu ◽  
D. M. Baekey ◽  
N. G. Maling ◽  
J. C. Sanchez ◽  
P. J. Reier ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Phrenic Nerve ◽  
Discharge Rate ◽  
Nerve Activity ◽  
Adult Rats ◽  
Phrenic Nerve Activity ◽  
Monosynaptic Connection ◽  
Nerve Signal ◽  
Phrenic Motoneurons ◽  
Discharge Patterns

Anatomical evidence indicates that midcervical interneurons can be synaptically coupled with phrenic motoneurons. Accordingly, we hypothesized that interneurons in the C3–C4 spinal cord can display discharge patterns temporally linked with inspiratory phrenic motor output. Anesthetized adult rats were studied before, during, and after a 4-min bout of moderate hypoxia. Neuronal discharge in C3–C4 lamina I–IX was monitored using a multielectrode array while phrenic nerve activity was extracellularly recorded. For the majority of cells, spike-triggered averaging (STA) of ipsilateral inspiratory phrenic nerve activity based on neuronal discharge provided no evidence of discharge synchrony. However, a distinct STA phrenic peak with a 6.83 ± 1.1 ms lag was present for 5% of neurons, a result that indicates a monosynaptic connection with phrenic motoneurons. The majority (93%) of neurons changed discharge rate during hypoxia, and the diverse responses included both increased and decreased firing. Hypoxia did not change the incidence of STA peaks in the phrenic nerve signal. Following hypoxia, 40% of neurons continued to discharge at rates above prehypoxia values (i.e., short-term potentiation, STP), and cells with initially low discharge rates were more likely to show STP ( P < 0.001). We conclude that a population of nonphrenic C3–C4 neurons in the rat spinal cord is synaptically coupled to the phrenic motoneuron pool, and these cells can modulate inspiratory phrenic output. In addition, the C3–C4 propriospinal network shows a robust and complex pattern of activation both during and following an acute bout of hypoxia.

scholarly journals Modules in the brain stem and spinal cord underlying motor behaviors

2011 ◽  
Vol 106 (3) ◽  
pp. 1363-1378 ◽  
Author(s):  
Jinsook Roh ◽  
Vincent C. K. Cheung ◽  
Emilio Bizzi
Keyword(s):  
Spinal Cord ◽  
Brain Stem ◽  
Muscle Synergies ◽  
Motor Behaviors ◽  
Leg Muscles ◽  
Before And After ◽  
The Central Nervous System ◽  
Almost All ◽  
Open Question ◽  
The Brain

Previous studies using intact and spinalized animals have suggested that coordinated movements can be generated by appropriate combinations of muscle synergies controlled by the central nervous system (CNS). However, which CNS regions are responsible for expressing muscle synergies remains an open question. We address whether the brain stem and spinal cord are involved in expressing muscle synergies used for executing a range of natural movements. We analyzed the electromyographic (EMG) data recorded from frog leg muscles before and after transection at different levels of the neuraxis—rostral midbrain (brain stem preparations), rostral medulla (medullary preparations), and the spinal-medullary junction (spinal preparations). Brain stem frogs could jump, swim, kick, and step, while medullary frogs could perform only a partial repertoire of movements. In spinal frogs, cutaneous reflexes could be elicited. Systematic EMG analysis found two different synergy types: 1) synergies shared between pre- and posttransection states and 2) synergies specific to individual states. Almost all synergies found in natural movements persisted after transection at rostral midbrain or medulla but not at the spinal-medullary junction for swim and step. Some pretransection- and posttransection-specific synergies for a certain behavior appeared as shared synergies for other motor behaviors of the same animal. These results suggest that the medulla and spinal cord are sufficient for the expression of most muscle synergies in frog behaviors. Overall, this study provides further evidence supporting the idea that motor behaviors may be constructed by muscle synergies organized within the brain stem and spinal cord and activated by descending commands from supraspinal areas.

Phrenic motoneuron discharge during sustained inspiratory resistive loading

1996 ◽  
Vol 81 (5) ◽  
pp. 2260-2266 ◽  
Author(s):  
Steve Iscoe
Keyword(s):  
Phrenic Nerve ◽  
Transdiaphragmatic Pressure ◽  
Phrenic Motoneurons ◽  
Resistive Loading ◽  
Instantaneous Discharge ◽  
Unidentified Source ◽  
Phrenic Motoneuron ◽  
Discharge Patterns ◽  
End Tidal ◽  
Spontaneously Breathing

Iscoe, Steve. Phrenic motoneuron discharge during sustained inspiratory resistive loading. J. Appl. Physiol. 81(5): 2260–2266, 1996.—I determined whether prolonged inspiratory resistive loading (IRL) affects phrenic motoneuron discharge, independent of changes in chemical drive. In seven decerebrate spontaneously breathing cats, the discharge patterns of eight phrenic motoneurons from filaments of one phrenic nerve were monitored, along with the global activity of the contralateral phrenic nerve, transdiaphragmatic pressure, and fractional end-tidal CO2 levels. Discharge patterns during hyperoxic CO2 rebreathing and breathing against an IRL (2,500–4,000 cmH2O ⋅ l−1 ⋅ s) were compared. During IRL, transdiaphragmatic pressure increased and then either plateaued or decreased. At the highest fractional end-tidal CO2 common to both runs, instantaneous discharge frequencies in six motoneurons were greater during sustained IRL than during rebreathing, when compared at the same time after the onset of inspiration. These increased discharge frequencies suggest the presence of a load-induced nonchemical drive to phrenic motoneurons from unidentified source(s).

scholarly journals Synchronous and asynchronous electrically evoked motor activities during wind-up stimulation are differentially modulated following an acute spinal transection

2012 ◽  
Vol 108 (12) ◽  
pp. 3322-3332 ◽  
Author(s):  
Alain Frigon ◽  
Marie-France Hurteau ◽  
Michael D. Johnson ◽  
C. J. Heckman ◽  
Alessandro Telonio ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Neuronal Excitability ◽  
Compound Action Potential ◽  
Spinal Transection ◽  
Reflex Responses ◽  
Neuronal Mechanisms ◽  
Before And After ◽  
Motor Activities ◽  
Electrical Pulses ◽  
Adult Cats

In this study, we used a novel technique to study reflex wind-up when the spinal cord is intact and following an acute spinal transection. Specifically, we evaluated reflex responses evoked by a series of 10 electrical pulses to the tibial or superficial peroneal nerves in 9 decerebrate adult cats, before and after an acute spinal transection. Electromyograms were recorded in four hindlimb muscles (lateral gastrocnemius, tibialis anterior, semitendinosus, and sartorius) to evaluate reflex amplitude, duration, and the temporal summation of reflex responses, so-called wind-up. We identified two distinct reflex responses evoked by electrical stimulation of the tibial or superficial peroneal nerves on the basis of their pattern of change following acute spinal transection, a short-latency (∼10 ms) compound action potential (CAP) that was followed by a burst of sustained activity (SA). Wind-up of CAP and SA amplitudes was clearly present when the spinal cord was intact but was drastically reduced after acute spinalization in some muscles. Moreover, CAP and SA reflex responses were differentially modified by the acute spinalization. When the effects of acute spinal transection were significant, CAP responses were increased after acute spinalization, whereas SA responses were reduced, suggesting that the two signals are regulated by different neuronal mechanisms. The present results provide the first assessment of reflex wind-up before and after an acute spinal transection in the same animals and indicate that different reflex components must be considered separately when evaluating changes in neuronal excitability following SCI.

Cervical sympathetic and phrenic nerve responses to progressive brain hypoxia

1990 ◽  
Vol 68 (1) ◽  
pp. 53-58 ◽  
Author(s):  
M. J. Wasicko ◽  
J. E. Melton ◽  
J. A. Neubauer ◽  
N. Krawciw ◽  
N. H. Edelman
Keyword(s):  
Blood Pressure ◽  
Phrenic Nerve ◽  
Progressive Reduction ◽  
Nerve Activity ◽  
Brain Hypoxia ◽  
Activity Peak ◽  
Inspiratory Activity ◽  
Cervical Sympathetic ◽  
End Tidal ◽  
End Tidal Co2

To determine if depression of central respiratory output during progressive brain hypoxia (PBH) can be generalized to other brain stem outputs, we examined the effect of PBH on the tonic (tSCS) and inspiratory-synchronous (iSCS) components of preganglionic superior cervical sympathetic (SCS) nerve activity. Peak phrenic and SCS activity were measured in nine anesthetized, paralyzed, peripherally chemodenervated, vagotomized cats. PBH was produced by inhalation of 0.5% CO in 40% O2 while blood pressure and end-tidal CO2 were maintained constant. A progressive reduction in arterial O2 content from 14.3 +/- 0.6 to 4.5 +/- 0.3 vol% caused a 79 +/- 7% depression of peak phrenic activity and an 84 +/- 10% reduction of iSCS activity, but tSCS activity increased 42 +/- 21%. During CO2 rebreathing, iSCS activity increased in parallel with peak phrenic activity while tSCS activity was unchanged. The slopes of the CO2 responses of both phrenic (6.3 +/- 1.2%max/mmHg) and iSCS (4.6 +/- 0.8%max/mmHg) activity were unaffected by PBH. In four of nine hypocapnic and three of nine hypoxic studies, inspiratory activity in the SCS nerve was observed even after completely silencing the phrenic neurogram.(ABSTRACT TRUNCATED AT 250 WORDS)

Evidence that C1 and C2 propriospinal neurons mediate the inhibitory effects of viscerosomatic spinal afferent input on primate spinothalamic tract neurons

1992 ◽  
Vol 67 (4) ◽  
pp. 852-860 ◽  
Author(s):  
S. F. Hobbs ◽  
U. T. Oh ◽  
M. J. Chandler ◽  
Q. G. Fu ◽  
D. C. Bolser ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Cell Activity ◽  
Inhibitory Effect ◽  
Afferent Input ◽  
Spinothalamic Tract ◽  
Spinal Transection ◽  
Thoracic Spinal Cord ◽  
Thoracic Spinal ◽  
Before And After ◽  
Propriospinal Neurons

1. Lumbosacral spinothalamic tract (STT) neurons can be inhibited by noxious pinch of the contralateral hindlimb or either forelimb and by electrical stimulation of cardiopulmonary sympathetic, splanchnic, and hypogastric afferents. A previous study found that spinal transections between C2 and C4 sometimes abolished the inhibitory effect of spinal afferent input and sometimes left it intact. This suggested that propriospinal neurons in the C1 and C2 segments might mediate this effect. To test whether neurons in the C1 and C2 segments were involved in producing this inhibitory effect, the magnitude of the reduction in neural activity was measured in the same STT neuron before and after spinal transection at C1 or between C3 and C7. 2. All neurons were antidromically activated from the contralateral thalamus and thoracic spinal cord. For us to accept a neuron for analysis, the characteristics of the somatic input and the latency and shape of the antidromatic spike produced by spinal cord stimulation had to be the same before and after the spinal transection. Also, spinal transection often causes a marked increase in spontaneous cell activity, which may affect the magnitude of an inhibitory response. To avoid this confounding problem, a cell was accepted for analysis only if it showed marked inhibition of high cell activity evoked by somatic pinch before spinal transection. For analysis 13 STT neurons met these criteria: 6 neurons were in monkeys with C1 transections, and 7 neurons were in animals with transections between C3 and C7.(ABSTRACT TRUNCATED AT 250 WORDS)

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