Cervical sympathetic and phrenic nerve responses to progressive brain hypoxia

Wasicko, M. J.; Melton, J. E.; Neubauer, Judith A.; Krawciw, N.; Edelman, Norman H.

doi:10.1152/jappl.1990.68.1.53

Cited by 30 publications

(22 citation statements)

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“…In the neonate, the decline in respiration is more pronounced and occurs more rapidly. Reduction of arterial oxygen content by 50% to 60% produces apnea in anesthetized, peripherally chemodenervated animals 40 . Further reduction of oxygen results in gasping movements that likely represent a hyperexcitable state prior to nerve cell membrane instability.…”

Section: Discussionmentioning

confidence: 99%

Correlation of Laryngeal Chemoreflex Severity With Laryngeal Muscle Response

Goding

1998

The Laryngoscope

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Objectives: To examine the relationship between the severity of the laryngeal chemoreflex (LCR) and the pattern of laryngeal muscle activity during an LCR‐induced apnea. Methods: The laryngeal mucosa of 20 piglets aged 17 to 20 days was stimulated under both hypoxic and normoxic conditions. Respiration, blood pressure, and activity of the thyroarytenoid (TA) and posterior cricoarytenoid (PCA) muscles were monitored during the LCR‐induced apnea. Results: Hypoxemia resulted in a shorter average apnea duration but a greater degree of hypotension. All piglets recovered spontaneously following normoxic LCR stimulation. Hypoxic stimulation resulted in two divergent apneic responses: transient with a spontaneous recovery (17 piglets) or profound requiring resuscitation (three piglets). An increase in TA muscle activity and a decrease in PCA muscle activity was the most common response to LCR stimulation. The response of the TA and PCA muscles was maintained in piglets destined for spontaneous recovery. Decreasing TA activity and increasing PCA activity correlated with the development of a profound response. Conclusions: The piglet demonstrates two distinct responses to hypoxic laryngeal chemostimulation that correlate with the activity of the intrinsic laryngeal muscles. Failure to maintain the activity of the TA and PCA muscles during a profound response is associated with the development of severe cardiovascular instability. This study suggests that the critical event involving the LCR is the development of complications secondary to hypoxia.

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Section: Discussionmentioning

confidence: 99%

Correlation of Laryngeal Chemoreflex Severity With Laryngeal Muscle Response

Goding

1998

The Laryngoscope

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“…However, work done by us and others also suggests that, in addition to the peripheral chemoreceptors, there are central hypoxia-sensitive cardiorespiratory sites that may also be important for the cardiorespiratory adaptations to chronic hypoxia (30,33,44). Two of these brain regions are within the rostral ventrolateral medulla (RVLM), the C1 sympathoexcitatory region, and the pre-Bötzinger complex (pre-BötC).…”

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confidence: 99%

Heme oxygenase-1-dependent central cardiorespiratory adaptations to chronic hypoxia in mice

Sunderram

Semmlow

Thakker‐Varia

et al. 2009

American Journal of Physiology-Regulatory, Integrative and Comp

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Adaptations to chronic hypoxia (CH) could reflect cellular changes within the cardiorespiratory regions of the rostral ventrolateral medulla (RVLM), the C1 region, and the pre-Bötzinger complex (pre-BötC). Previous studies have shown that the hypoxic chemosensitivity of these regions are heme oxygenase (HO) dependent and that CH induces HO-1. To determine the time course of HO-1 induction within these regions and explore its relevance to the respiratory and sympathetic responses during CH, the expression of HO-1 mRNA and protein in the RVLM and measures of respiration, sigh frequency, and sympathetic activity (spectral analysis of heart rate) were examined during 10 days of CH. Respiratory and sympathetic responses to acute hypoxia were obtained in chronically instrumented awake wild-type (WT) and HO-1 null mice. After 4 days of CH, there was a significant induction of HO-1 within the C1 region and pre-BötC. WT mice acclimated to CH by increasing peak diaphragm EMG after 10 days of CH but had no change in the respiratory response to acute hypoxia. There were no significant differences between WT and HO-1 null mice. In WT mice, hypoxic sigh frequency and hypoxic sensitivity of sympathetic activity initially declined before returning toward baseline after 5 days of CH, correlating with the induction of HO-1. In contrast, HO-1 null mice had a persistent decline in hypoxic sigh frequency and hypoxic sensitivity of sympathetic activity. We conclude that induction of HO-1 in these RVLM cardiorespiratory regions may be important for the hypoxic sensitivity of sighs and sympathetic activity during CH.

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“…However, the populations of neurons that are involved in such regulation have been shown to have different responses to central hypoxia, leading to increases or decreases in respiratory or sympathetic output (51).…”

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confidence: 99%

Hypoxic excitation in neurons cultured from the rostral ventrolateral medulla of the neonatal rat

Mazza¹,

Edelman

Neubauer³

2000

Journal of Applied Physiology

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Neurons within cardiorespiratory regions of the rostral ventrolateral medulla (RVLM) have been shown to be excited by local hypoxia. To determine the electrophysiological properties of these excitatory responses to hypoxia, we developed a primary dissociated cell culture system to examine the intrinsic response of RVLM neurons to hypoxia. Neonatal rat neurons plated on medullary astrocyte monolayers were studied using the whole cell perforated patch-clamp technique. Sodium cyanide (NaCN, 0.5-10 mM) was used, and membrane potential (V(m)), firing frequency, and input resistance were examined. In 11 of 19 neurons, NaCN produced a V(m) depolarization, an increase in firing frequency, and a decrease in input resistance, suggesting the opening of a cation channel. The hypoxic depolarization had a linear dose response and was dependent on baseline V(m), with a greater response at more hyperpolarized V(m). In 8 of 19 neurons, NaCN produced a V(m) hyperpolarization, decrease in firing frequency, and variable changes in input resistance. The V(m) hyperpolarization exhibited an all-or-none dose response and was independent of baseline V(m). These differential responses to NaCN were retained after synaptic blockade with low Ca(2+)-high Mg(2+) or TTX. Thus hypoxic excitation 1) is maintained in cell culture, 2) is an intrinsic response, and 3) is likely due to the increase in a cation current. These hypoxia-excited neurons are likely candidates to function as central oxygen sensors.

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Cervical sympathetic and phrenic nerve responses to progressive brain hypoxia

Cited by 30 publications

References 0 publications

Correlation of Laryngeal Chemoreflex Severity With Laryngeal Muscle Response

Correlation of Laryngeal Chemoreflex Severity With Laryngeal Muscle Response

Heme oxygenase-1-dependent central cardiorespiratory adaptations to chronic hypoxia in mice

Hypoxic excitation in neurons cultured from the rostral ventrolateral medulla of the neonatal rat

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