Unique spectral peak in phrenic nerve activity characterizes gasps in decerebrate cats

The respiratory pattern of gasping has been characterized on the phrenic nerve as rapidonset, rapid-rise, large-amplitude bursts of neural activity. Furthermore, medullary sites critical for the neurogenesis of gasping have been identified and are not the sites of identified respiratory neurons, such as the dorsal and ventral respiratory groups. I classified envelopes of phrenic nerve activity as eupneic breaths, or gasps based on the time-domain features of duration, shape, and amplitude. Gasps were elicited by hypoxia and low blood pressure in 9 of 12 decerebrate cats. Inspiratory times were 1.15 +/- 0.43 (SD) for eupneic breaths and 0.55 +/- 0.18s for gasps. The high-frequency peaks in the power spectra of phrenic nerve activity were at 80 +/- 13 Hz for eupneic breaths and at 120 +/- 21 Hz for gasps. Three of the 12 cats developed a breathing pattern that began as a normal breath and terminated in a gasp. Power spectra of the normal portion had eupneic spectral peaks (75 +/- 24 Hz); power spectra of the gasp portion had the high peaks at 110 +/- 23 Hz, a value 1.5 times higher than that for the normal peaks. Although this analysis of peripheral nerve activity cannot distinguish between two central pattern generators at two distinct anatomical sites or one pattern generator operating in two distinct modes, the fact that gasps were much shorter in duration and had markedly higher spectral peaks than control breaths supports the idea that the central pattern generator for gasping is not the central pattern generator for eupnea.

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Sympathetic rhythms during hyperventilation-induced apnea

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1985.249.4.r424 ◽

1985 ◽

Vol 249 (4) ◽

pp. R424-R431 ◽

Cited By ~ 1

Author(s):

C. A. Connelly ◽

R. D. Wurster

Keyword(s):

Phrenic Nerve ◽

Sympathetic Nerve ◽

Sympathetic Activity ◽

Sympathetic Nerves ◽

Nerve Activity ◽

Phrenic Nerve Activity ◽

Bilateral Carotid Occlusion ◽

Bilateral Carotid ◽

Spectral Peaks ◽

Respiratory Modulation

The effect of hyperventilation-induced apnea on the respiratory rhythmicity of sympathetic nerve activity was determined using spectral analysis of sympathetic nerve frequencies. Left phrenic, external intercostal, and inferior cardiac sympathetic nerves were recorded in alpha-chloralose-anesthetized, vagotomized, paralyzed, artificially ventilated cats. The respiratory modulation of sympathetic activity during normoventilation was indicated by spectral peaks of sympathetic activity coinciding with respiratory frequencies determined from the phrenic nerve activity of each cat. The spectral peaks of respiratory-related sympathetic activity disappeared during hyperventilation-induced apnea and then reappeared with the return of phrenic nerve activity when normoventilation was resumed. Although sympathetic activity lost its respiratory modulation during hyperventilation, baroreceptor-mediated bilateral carotid occlusion responses and electrocardiogram (R wave)-triggered computer summation of cardiac related sympathetic activity were unaffected. Hence central respiratory inputs on sympathetic pathways in the central nervous system best explain the origin of respiratory-related sympathetic rhythms. Independent sympathetic rhythms of apparent nonrespiratory origin may be due to artificial ventilator influences, baroreflex-autonomic oscillation loops, or Mayer waves.

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Naloxone enhances respiratory output in cats

Journal of Applied Physiology ◽

10.1152/jappl.1979.47.5.1105 ◽

1979 ◽

Vol 47 (5) ◽

pp. 1105-1111 ◽

Cited By ~ 63

Author(s):

E. E. Lawson ◽

T. G. Waldrop ◽

F. L. Eldridge

Keyword(s):

Phrenic Nerve ◽

Opiate Receptors ◽

Physiological Role ◽

Opiate Antagonist ◽

Nerve Activity ◽

Phrenic Nerve Activity ◽

End Tidal ◽

Decerebrate Cats ◽

End Tidal Co2

To investigate the physiological role of opiate receptors and opiatelike neurotransmitters, which are present in brain-stem respiratory centers, we administered naloxone to 10 cats by intravenous injection. These animals were vagotomized, paralyzed, and servo-ventilated to maintain constant end-tidal CO2; in addition, their carotid sinus nerves were sectioned bilaterally. Respiratory output was assessed by integration of phrenic nerve activity. Control saline infusions had no effect on respiratory output. However, administration of naloxone (0.4 mg/kg) caused phrenic minute output to increase significantly in each of five anesthetized cerebrate cats (control 7,272 +/- 1,615 U/min; 30 min postnaloxone 12,920 +/- 3,857 U/min; P less than 0.05) and five unanesthetized decerebrate cats (control 10,368 +/- 1,222 U/min; naloxone 14,648 +/- 3,225 U/min; P less than 0.05). In addition to the effect on phrenic minute output, naloxone infusion resulted in an increase of the inspiratory rate of rise of phrenic nerve activity in each cat. There was no change in the ratio of inspiratory duration to total respiratory period (TI/Ttot). Because naloxone is a specific opiate antagonist, we suggest that endogenous opiatelike neurotransmitters (endorphins) may modulate central inspiratory drive.

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Entrainment pattern between sympathetic and phrenic nerve activities in the Sprague-Dawley rat: hypoxia-evoked sympathetic activity during expiration

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.00485.2003 ◽

2004 ◽

Vol 286 (6) ◽

pp. R1121-R1128 ◽

Cited By ~ 48

Author(s):

Thomas E. Dick ◽

Y.-H. Hsieh ◽

Shaun Morrison ◽

Sharon K. Coles ◽

Nanduri Prabhakar

Keyword(s):

Phrenic Nerve ◽

Sympathetic Activity ◽

Respiratory Pattern ◽

Sprague Dawley ◽

Short Term ◽

Nerve Activity ◽

Term Potentiation ◽

Motor Activities ◽

Respiratory Modulation ◽

Activity Dependent

Sympathetic and respiratory motor activities are entrained centrally. We hypothesize that this coupling may partially underlie changes in sympathetic activity evoked by hypoxia due to activity-dependent changes in the respiratory pattern. Specifically, we tested the hypothesis that sympathetic nerve activity (SNA) expresses a short-term potentiation in activity after hypoxia similar to that expressed in phrenic nerve activity (PNA). Adult male, Sprague-Dawley (Zivic Miller) rats ( n = 19) were anesthetized (Equithesin), vagotomized, paralyzed, ventilated, and pneumothoracotomized. We recorded PNA and splanchnic SNA (sSNA) and generated cycle-triggered averages (CTAs) of rectified and integrated sSNA before, during, and after exposures to hypoxia (8% O2 and 92% N2 for 45 s). Inspiration (I) and expiration (E) were divided in half, and the average and area of integrated sSNA were calculated and compared at the following time points: before hypoxia, at the peak breathing frequency during hypoxia, immediately before the end of hypoxia, immediately after hypoxia, and 60 s after hypoxia. In our animal model, sSNA bursts consistently followed the I-E phase transition. With hypoxia, sSNA increased in both halves of E, but preferentially in the second rather than the first half of E, and decreased in I. After hypoxia, sSNA decreased abruptly, but the coefficient of variation in respiratory modulation of sSNA was significantly less than that at baseline. The hypoxic-evoked changes in sympathetic activity and respiratory pattern resulted in sSNA in the first half of E being correlated negatively to that in the second half of E ( r = −0.65, P < 0.05) and positively to Te ( r = 0.40, P < 0.05). Short-term potentiation in sSNA appeared not as an increase in the magnitude of activity but as an increased consistency of its respiratory modulation. By 60 s after hypoxia, the variability in the entrainment pattern had returned to baseline. The preferential recruitment of late expiratory sSNA during hypoxia results from either activation by expiratory-modulated neurons or by non-modulated neurons whose excitatory drive is not gated during late E.

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Behavior-Dependent Activities of a Central Pattern Generator in Freely Behaving Lymnaea stagnalis

Journal of Neurophysiology ◽

10.1152/jn.1997.78.6.3415 ◽

1997 ◽

Vol 78 (6) ◽

pp. 3415-3427 ◽

Cited By ~ 7

Author(s):

Rene F. Jansen ◽

Anton W. Pieneman ◽

Andries ter Maat

Keyword(s):

Electrical Activity ◽

Central Pattern Generator ◽

Lymnaea Stagnalis ◽

Central Pattern Generators ◽

Pattern Generator ◽

Egg Laying ◽

Buccal Ganglion ◽

Level Of Activity ◽

Freely Behaving ◽

Pattern Generators

Jansen, Rene F., Anton W. Pieneman, and Andries ter Maat. Behavior-dependent activities of a central pattern generator in freely behaving Lymnaea stagnalis. J. Neurophysiol. 78: 3415–3427, 1997. Cyclic or repeated movements are thought to be driven by networks of neurons (central pattern generators) that are dynamic in their connectivity. During two unrelated behaviors (feeding and egg laying), we investigated the behavioral output of the buccal pattern generator as well as the electrical activity of a pair of identified interneurons that have been shown to be involved in setting the level of activity of this pattern generator (PG). Analysis of the quantile plots of the parameters that describe the behavior (movements of the buccal mass) reveals that during egg laying, the behavioral output of the PG is different compared with that during feeding. Comparison of the average durations of the different parts of the buccal movements showed that during egg laying, the duration of one specific part of buccal movement is increased. Correlated with these changes in the behavioral output of the PG were changes in the firing rate of the cerebral giant neurons (CGC), a pair of interneurons that have been shown to modulate the activity of the PG by means of multiple synaptic contacts with neurons in the buccal ganglion. Interval- and autocorrelation histograms of the behavioral output and CGC spiking show that both the PG output and the spiking properties of the CGCs are different when comparing egg-laying animals with feeding animals. Analysis of the timing relations between the CGCs and the behavioral output of the PG showed that both during feeding and egg laying, the electrical activity of the CGCs is largely in phase with the PG output, although small changes occur. We discuss how these results lead to specific predictions about the kinds of changes that are likely to occur when the animal switches the PG from feeding to egg laying and how the hormones that cause egg laying are likely to be involved.

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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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