Phrenic nerve activity and occlusion pressure changes during CO2 rebreathing in cats

Changes in phrenic nerve activity, quantified as a moving time average, PNG(t), were characterized during complete airway occlusion at functional residual capacity (FRC) and compared to simultaneously occurring changes in intratracheal pressure. In anesthetized cats breathing room air and during CO2 breathing, PNG(t) during occlusion was the same as that found during unobstructed breathing until it reached a value approximately corresponding to that at peak inspiration in the preceding unoccluded breath, the rate of change of PNG(t) usually remained the same but in a few cases (2 out of 11)increased. When intratracheal occlusion pressure was plotted as a function of PNG(t), both while breathing room air and during CO2 rebreathing, an approximately linear relationship was obtained. Thus, changes in intratracheasocclusion pressure obtained at FRC parallel changes in phrenic motor nerve activity. Quantification of electrical activity of respiratory nerves as a moving time average provides a means of characterizing changes in the average level of electrical activity during an inspiratory effort.

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Patterns of neural and muscular electrical activity in costal and crural portions of the diaphragm

Journal of Applied Physiology ◽

10.1152/jappl.1989.66.5.2092 ◽

1989 ◽

Vol 66 (5) ◽

pp. 2092-2100 ◽

Cited By ~ 14

Author(s):

L. M. Oyer ◽

S. L. Knuth ◽

D. K. Ward ◽

D. Bartlett

Keyword(s):

Electrical Activity ◽

Phrenic Nerve ◽

Respiratory Activity ◽

Respiratory Muscles ◽

Emg Activity ◽

Neural Responses ◽

Nerve Activity ◽

Phrenic Nerve Activity ◽

Central Respiratory Activity ◽

Spontaneously Breathing

To determine whether the central respiratory drives to costal and crural portions of the diaphragm differ from each other in response to chemical and mechanical feedbacks, activities of costal and crural branches of the phrenic nerve were recorded in decerebrate paralyzed cats, studied either with vagi intact and servo-ventilated in accordance with their phrenic nerve activity or vagotomized and ventilated conventionally. Costal and crural electromyograms (EMGs) were recorded in decerebrate spontaneously breathing cats. Hypercapnia and hypoxia resulted in significant increases in peak integrated costal, crural, and whole phrenic nerve activities when the vagi were either intact or cut. However, there were no consistent differences between costal and crural neural responses. Left crural EMG activity was increased significantly more than left costal EMG activity in response to hypercapnia and hypoxia. These results indicate that the central neural inputs to costal and crural portions of the diaphragm are similar in eupnea and in response to chemical and mechanical feedback in decerebrate paralyzed cats. The observed differences in EMG activities in spontaneously breathing animals must arise from modulation of central respiratory activity by mechanoreceptor feedback from respiratory muscles, likely the diaphragm itself.

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Microinjections of glycine into the pre-Bötzinger complex inhibit phrenic nerve activity in the rat

Brain Research ◽

10.1016/s0006-8993(02)02902-5 ◽

2002 ◽

Vol 947 (1) ◽

pp. 25-33 ◽

Cited By ~ 7

Author(s):

V.C Chitravanshi ◽

H.N Sapru

Keyword(s):

Phrenic Nerve ◽

Nerve Activity ◽

Phrenic Nerve Activity ◽

Bötzinger Complex

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Daily acute intermittent hypoxia enhances phrenic motor output and stimulus-evoked phrenic responses in rats

Journal of Neurophysiology ◽

10.1152/jn.00112.2021 ◽

2021 ◽

Author(s):

Raphael Rodrigues Perim ◽

Michael D. Sunshine ◽

Joseph F. Welch ◽

Juliet Santiago ◽

Ashley Holland ◽

...

Keyword(s):

Motor Neurons ◽

Phrenic Nerve ◽

Intermittent Hypoxia ◽

Neural Control ◽

Respiratory Cycle ◽

Evoked Responses ◽

Nerve Activity ◽

Synaptic Inputs ◽

Phrenic Nerve Activity ◽

The Impact

Plasticity is a hallmark of the respiratory neural control system. Phrenic long-term facilitation (pLTF) is one form of respiratory plasticity characterized by persistent increases in phrenic nerve activity following acute intermittent hypoxia (AIH). Although there is evidence that key steps in the cellular pathway giving rise to pLTF are localized within phrenic motor neurons (PMNs), the impact of AIH on the strength of breathing-related synaptic inputs to PMNs remains unclear. Further, the functional impact of AIH is enhanced by repeated/daily exposure to AIH (dAIH). Here, we explored the effects of AIH vs. 2 weeks of dAIH preconditioning on spontaneous and evoked responses recorded in anesthetized, paralyzed (with pancuronium bromide) and mechanically ventilated rats. Evoked phrenic potentials were elicited by respiratory cycle-triggered lateral funiculus stimulation at C2 delivered prior to- and 60 min post-AIH (or an equivalent time in controls). Charge-balanced biphasic pulses (100 µs/phase) of progressively increasing intensity (100 to 700 µA) were delivered during the inspiratory and expiratory phases of the respiratory cycle. Although robust pLTF (~60% from baseline) was observed after a single exposure to moderate AIH (3 x 5 min; 5 min intervals), there was no effect on evoked phrenic responses, contrary to our initial hypothesis. However, in rats preconditioned with dAIH, baseline phrenic nerve activity and evoked responses were increased, suggesting that repeated exposure to AIH enhances functional synaptic strength when assessed using this technique. The impact of daily AIH preconditioning on synaptic inputs to PMNs raises interesting questions that require further exploration.

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The neuromuscular basis of rhythmic struggling movements in embryos of Xenopus laevis

Journal of Experimental Biology ◽

10.1242/jeb.99.1.197 ◽

1982 ◽

Vol 99 (1) ◽

pp. 197-205 ◽

Cited By ~ 2

Author(s):

J. A. Kahn ◽

A. Roberts

Keyword(s):

Xenopus Laevis ◽

Electrical Activity ◽

Central Pattern Generator ◽

Large Amplitude ◽

Motor Nerve ◽

Sensory Stimulation ◽

Pattern Generator ◽

Rhythmic Movements ◽

Nerve Activity ◽

Xenopus Embryos

Xenopus embryos struggle when restrained. Struggling involves rhythmic movements of large amplitude, in which waves of bending propagate from the tail to the head. Underlying this, electrical activity in myotomal muscles occurs in rhythmic bursts that alternate on either side of a segment. Bursts in ipsilateral segments occur in a caudo-rostral sequence. Curarized embryos can generate motor nerve activity in a struggling pattern in the absence of rhythmic sensory stimulation; the pattern is therefore produced by a central pattern generator.

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Evaluation of a New Valveless all Purpose Ventilator: Effect of Ventilating Frequency PEEP, PACO2 and PAO2 on Phrenic Nerve Activity

Perspectives in High Frequency Ventilation - Developments in Critical Care Medicine and Anesthesiology ◽

10.1007/978-94-009-6711-3_15 ◽

1983 ◽

pp. 140-145 ◽

Cited By ~ 2

Author(s):

M. K. Chakrabarti ◽

J. G. Whitwam

Keyword(s):

Phrenic Nerve ◽

Nerve Activity ◽

Phrenic Nerve Activity

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Effects of hypercapnia and hypoxia on phrenic nerve activity and respiratory timing

Journal of Applied Physiology ◽

10.1152/jappl.1981.51.3.732 ◽

1981 ◽

Vol 51 (3) ◽

pp. 732-738 ◽

Cited By ~ 18

Author(s):

J. F. Ledlie ◽

S. G. Kelsen ◽

N. S. Cherniack ◽

A. P. Fishman

Keyword(s):

Phrenic Nerve ◽

Carotid Sinus ◽

Peak Height ◽

Inspiratory Time ◽

Nerve Activity ◽

Phrenic Nerve Activity ◽

Chemical Stimuli ◽

Proprioceptive Inputs ◽

Spontaneously Breathing ◽

Respiratory Responses

In the spontaneously breathing animal, respiratory responses to chemical stimuli are influenced by phasic proprioceptive inputs from the thorax. We have compared the effects of hypercapnia and hypoxia on the level and timing of phrenic nerve activity while these phasic afferent signals were absent. Progressive hyperoxic hypercapnia and isocapnic hypoxia were produced in anesthetized paralyzed dogs by allowing 3–5 min of apnea to follow mechanical ventilation with 100% O2 or 35% O2 in N2, respectively; during hypoxia, isocapnia was maintained by intravenous infusion of tris(hydroxymethyl)aminomethane buffer. The peak height (P) of nerve bursts, inspiratory time (TI), and expiratory time (TE) were measured from the phrenic neurogram. With the vagi intact or severed, hypoxia decreased TI, whereas hypercapnia did not; both stimuli decreased TE. At the same minute phrenic activity (P x frequency), P, TI, and TE were all less during hypoxia than during hypercapnia. The decreases in TI and TE with hypoxia were significantly less after carotid sinus denervation. The results indicate that the patterns of phrenic nerve activity in response to hypoxia and hypercapnia are different: hypoxia has a greater effect on respiratory timing, whereas hypercapnia has a greater effect on peak phrenic nerve activity. The effect of hypoxia on respiratory timing is largely mediated by the peripheral chemoreceptors.

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