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The Journal of Comparative Neurology Dec 2018Structural plasticity in motoneurons may be influenced by activation history and motoneuron-muscle fiber interactions. The goal of this study was to examine the...
Structural plasticity in motoneurons may be influenced by activation history and motoneuron-muscle fiber interactions. The goal of this study was to examine the morphological adaptations of phrenic motoneurons following imposed motoneuron inactivity while controlling for diaphragm muscle inactivity. Well-characterized rat models were used including unilateral C2 spinal hemisection (SH; ipsilateral phrenic motoneurons and diaphragm muscle are inactive) and tetrodotoxin phrenic nerve blockade (TTX; ipsilateral diaphragm muscle is paralyzed while phrenic motoneuron activity is preserved). We hypothesized that inactivity of phrenic motoneurons would result in a decrease in motoneuron size, consistent with a homeostatic increase in excitability. Phrenic motoneurons were retrogradely labeled by ipsilateral diaphragm muscle injection of fluorescent dextrans or cholera toxin subunit B. Following 2 weeks of diaphragm muscle paralysis, morphological parameters of labeled ipsilateral phrenic motoneurons were assessed quantitatively using fluorescence confocal microscopy. Compared to controls, phrenic motoneuron somal volumes and surface areas decreased with SH, but increased with TTX. Total phrenic motoneuron surface area was unchanged by SH, but increased with TTX. Dendritic surface area was estimated from primary dendrite diameter using a power equation obtained from three-dimensional reconstructed phrenic motoneurons. Estimated dendritic surface area was not significantly different between control and SH, but increased with TTX. Similarly, TTX significantly increased total phrenic motoneuron surface area. These results suggest that ipsilateral phrenic motoneuron morphological adaptations are consistent with a normalization of motoneuron excitability following prolonged alterations in motoneuron activity. Phrenic motoneuron structural plasticity is likely more dependent on motoneuron activity (or descending input) than muscle fiber activity.
Topics: Animals; Diaphragm; Disease Models, Animal; Motor Neurons; Neuronal Plasticity; Phrenic Nerve; Rats; Rats, Sprague-Dawley; Respiratory Paralysis
PubMed: 30411341
DOI: 10.1002/cne.24503 -
Postgraduate Medical Journal Jul 1977A case is reported of diaphragmatic flutter with an unusually long duration of symptoms. The patient described demonstrates many of the classical features of this...
A case is reported of diaphragmatic flutter with an unusually long duration of symptoms. The patient described demonstrates many of the classical features of this disorder.
Topics: Adolescent; Diaphragm; Electrocardiography; Female; Humans; Phonocardiography; Phrenic Nerve
PubMed: 882482
DOI: 10.1136/pgmj.53.621.399 -
The Journal of Physiology Oct 2002We aimed in this study to elucidate the discharge properties and neuronal mechanisms of the dissociation between hypoglossal and phrenic inspiratory activities in...
We aimed in this study to elucidate the discharge properties and neuronal mechanisms of the dissociation between hypoglossal and phrenic inspiratory activities in decerebrate rats, which had been subjected to neuromuscular blockade and artificially ventilated. The discharge of the hypoglossal nerve and the intracellular activity of hypoglossal motoneurones were monitored during respiration and fictive-swallowing evoked by electrical stimulation of the superior laryngeal nerve, and were compared with the activity of the phrenic nerve. The hypoglossal nerve activity was characterized by its onset preceding the phrenic nerve activity ('pre-I' activity). By manipulating artificial respiration, we could augment the 'pre-I' activity, and could elicit another type of hypoglossal activity decoupled from the phrenic-associated inspiratory bursts ('decoupled' activity). We further scrutinized the correlatives of 'pre-I' and 'decoupled' activities in individual hypoglossal motoneurones. Hypoglossal motoneurones consisted of inspiratory (n = 42), expiratory (n = 18) and non-respiratory (n = 1) neurones and were classified by their swallowing activity into depolarized, hyperpolarized, hyperpolarized-depolarized and unresponsive groups. All of the inspiratory neurones were depolarized in accordance with the 'pre-I' and 'decoupled' activities, and all of the expiratory neurones were hyperpolarized during these activities. Fictive swallowing, which was characterized by its frequent emergence just after the phrenic inspiratory activity, was also evoked just after the 'decoupled' hypoglossal activity, suggesting that this activity may have similar effects on swallowing as the 'overt' inspiratory activity. Such a coupling between 'decoupled' and swallowing activities was also revealed in each motoneurone. These findings suggest that the 'pre-I' and 'decoupled' activities may reflect some internal inspiratory activity of the respiratory centre and that hypoglossal motoneurones may be driven by a distinct group of premotor neurones that possibly play a role in the coordination of respiration and swallowing.
Topics: Animals; Decerebrate State; Deglutition; Electric Stimulation; Electrophysiology; Hypoglossal Nerve; Laryngeal Nerves; Male; Motor Neurons; Phrenic Nerve; Rats; Respiratory Physiological Phenomena
PubMed: 12356891
DOI: 10.1113/jphysiol.2002.022566 -
Kardiologia Polska Sep 2019Cryoablation is an effective and safe method of pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF). However, monitoring of phrenic nerve...
BACKGROUND
Cryoablation is an effective and safe method of pulmonary vein isolation (PVI) for the treatment of atrial fibrillation (AF). However, monitoring of phrenic nerve function during cryoballoon PVI remains an important issue.
AIMS
We aimed to compare 2 techniques of phrenic nerve stimulation (PNS) with the use of either a straight or a crosier‑shaped decapolar deflectable catheter.
METHODS
The study included 218 patients (mean [SD] age, 61.8 [10.9] years; 87 women) referred for cryoballoon PVI for AF. Patients were randomly assigned to PNS with either a straight or a crosier‑shaped catheter.
RESULTS
The groups did not differ in demographic characteristics or PVI effectiveness. The current threshold during PNS was lower in the group in which the crosier‑shaped catheter was applied (mean [SD], 6.7 [4.9] mA vs 4.8 [3.7] mA; P <0.01). In this group, the procedure time was shorter (mean [SD], 72.6 [22.8] min vs 64.4 [14.8] min; P <0.01), fewer repositioning maneuvers were required (31.8% vs 19.4%; P <0.05), and atrial capture during PNS was observed more frequently (11.5% vs 29.6%; P <0.01).
CONCLUSIONS
Straight and crosier‑shaped catheter techniques are equally effective in monitoring for phrenic nerve palsy. The crosier‑shaped catheter maintains its position better, thus leading to fewer dislocations and requiring fewer correction maneuvers, which might correlate with shorter procedure time. Moreover, this technique provides lower pacing thresholds. Both techniques may be safely used in patients with AF, and if stable phrenic nerve capture cannot be achieved, switching to another technique seems reasonable.
Topics: Aged; Atrial Fibrillation; Catheter Ablation; Female; Humans; Male; Middle Aged; Phrenic Nerve; Prospective Studies; Pulmonary Veins; Treatment Outcome
PubMed: 31354159
DOI: 10.33963/KP.14908 -
The Journal of Physiology Sep 2003All respiratory long-term facilitation (LTF) is induced by inspiratory-excitatory stimulation, suggesting that LTF needs inspiratory augmentation and is the result of a...
All respiratory long-term facilitation (LTF) is induced by inspiratory-excitatory stimulation, suggesting that LTF needs inspiratory augmentation and is the result of a Hebbian mechanism (coincident pre- and post-synaptic activity strengthens synapses). The present study examined the long-term effects of episodic inspiratory-inhibitory vagus nerve stimulation (VNS) on phrenic nerve activity. We hypothesized that episodic VNS would induce phrenic long-term depression. The results are compared with those obtained following serotonin receptor antagonism or episodic carotid sinus nerve stimulation (CSNS). Integrated phrenic neurograms were measured before, during and after three episodes of 5 min VNS (50 Hz, 0.1 ms), each separated by a 5 min interval, at a low (approximately 50 microA), medium (approximately 200 microA) or high (approximately 500 microA) stimulus intensity in anaesthetized, vagotomized, neuromuscularly blocked and artificially ventilated rats. Medium- and high-intensity VNS eliminated rhythmic phrenic activity during VNS, while low-intensity VNS only reduced phrenic burst frequency. At 60 min post-VNS, phrenic amplitude was higher than baseline (35 +/- 5% above baseline, mean +/- S.E.M., P < 0.05) in the high-intensity group but not in the low- (-4 +/- 4%) or medium-intensity groups (-10 +/- 15%), or in the high-intensity with methysergide group (4 mg kg(-1), i.p.) (-11 +/- 5%). These data, which are inconsistent with our hypothesis, indicate that phrenic-inhibitory VNS induces a serotonin-dependent phrenic LTF similar to that induced by phrenic-excitatory CSNS (33 +/- 7%) and may require activation of high-threshold afferent fibres. These data also suggest that the synapses on phrenic motoneurons do not use the Hebbian mechanism in this LTF, as these motoneurons were suppressed during VNS.
Topics: Animals; Blood Pressure; Carbon Dioxide; Electric Stimulation; Long-Term Potentiation; Male; Motor Neurons; Neural Inhibition; Oxygen; Phrenic Nerve; Rats; Rats, Sprague-Dawley; Vagus Nerve
PubMed: 12872010
DOI: 10.1113/jphysiol.2003.048157 -
Journal of Cachexia, Sarcopenia and... Feb 2019Cancer cachexia is an insidious process characterized by muscle atrophy with associated motor deficits, including diaphragm weakness and respiratory insufficiency....
BACKGROUND
Cancer cachexia is an insidious process characterized by muscle atrophy with associated motor deficits, including diaphragm weakness and respiratory insufficiency. Although neuropathology contributes to muscle wasting and motor deficits in many clinical disorders, neural involvement in cachexia-linked respiratory insufficiency has not been explored.
METHODS
We first used whole-body plethysmography to assess ventilatory responses to hypoxic and hypercapnic chemoreflex activation in mice inoculated with the C26 colon adenocarcinoma cell line. Mice were exposed to a sequence of inspired gas mixtures consisting of (i) air, (ii) hypoxia (11% O ) with normocapnia, (iii) hypercapnia (7% CO ) with normoxia, and (iv) combined hypercapnia with hypoxia (i.e. maximal chemoreflex response). We also tested the respiratory neural network directly by recording inspiratory burst output from ligated phrenic nerves, thereby bypassing influences from changes in diaphragm muscle strength, respiratory mechanics, or compensation through recruitment of accessory motor pools.
RESULTS
Cachectic mice demonstrated a significant attenuation of the hypoxic tidal volume (0.26mL±0.01mL vs 0.30mL±0.01mL; p<0.05), breathing frequency (317±10bpm vs 344±6bpm; p<0.05) and phrenic nerve (29.5±2.6% vs 78.8±11.8%; p<0.05) responses. On the other hand, the much larger hypercapnic tidal volume (0.46±0.01mL vs 0.46±0.01mL; p>0.05), breathing frequency (392±5bpm vs 408±5bpm; p>0.05) and phrenic nerve (93.1±8.8% vs 111.1±13.2%; p>0.05) responses were not affected. Further, the concurrent hypercapnia/hypoxia tidal volume (0.45±0.01mL vs 0.45±0.01mL; p>0.05), breathing frequency (395±7bpm vs 400±3bpm; p>0.05), and phrenic nerve (106.8±7.1% vs 147.5±38.8%; p>0.05) responses were not different between C26 cachectic and control mice.
CONCLUSIONS
Breathing deficits associated with cancer cachexia are specific to the hypoxic ventilatory response and, thus, reflect disruptions in the hypoxic chemoafferent neural network. Diagnostic techniques that detect decompensation and therapeutic approaches that support the failing hypoxic respiratory response may benefit patients at risk for cancer cachectic-associated respiratory failure.
Topics: Animals; Cachexia; Cell Line, Tumor; Hypercapnia; Hypoxia; Male; Mice; Neoplasms; Phrenic Nerve; Plethysmography; Respiration
PubMed: 30362273
DOI: 10.1002/jcsm.12348 -
Acta Medica (Hradec Kralove) 2016In the current cadaveric study an unusual sizeable accessory phrenic nerve (APN) was encountered emerging from the trunk of the supraclavicular nerves and forming a...
In the current cadaveric study an unusual sizeable accessory phrenic nerve (APN) was encountered emerging from the trunk of the supraclavicular nerves and forming a triangular loop that was anastomosing with the phrenic nerve. That neural loop surrounded the superficial cervical artery which displayed a spiral course. The form of a triangular loop of APN involving the aforementioned artery and originating from the supraclavicular nerve to the best of our knowledge has not been documented previously in the literature. The variable morphological features of the APN along with its clinical applications are briefly discussed.
Topics: Aged; Arteries; Cervical Vertebrae; Humans; Male; Neck; Phrenic Nerve
PubMed: 27526310
DOI: 10.14712/18059694.2016.55 -
Brazilian Journal of Medical and... Jun 2011Ventilatory differences between rat strains and genders have been described but the morphology of the phrenic nerve has not been investigated in spontaneously... (Comparative Study)
Comparative Study
Ventilatory differences between rat strains and genders have been described but the morphology of the phrenic nerve has not been investigated in spontaneously hypertensive (SHR) and normotensive Wistar-Kyoto (WKY) rats. A descriptive and morphometric study of the phrenic nerves of male (N = 8) and female (N = 9) SHR, and male (N = 5) and female (N = 6) WKY is presented. After arterial pressure and heart rate recordings, the phrenic nerves of 20-week-old animals were prepared for epoxy resin embedding and light microscopy. Morphometric analysis performed with the aid of computer software that took into consideration the fascicle area and diameter, as well as myelinated fiber profile and Schwann cell nucleus number per area. Phrenic nerves were generally larger in males than in females on both strains but larger in WKY compared to SHR for both genders. Myelinated fiber numbers (male SHR = 228 ± 13; female SHR = 258 ± 4; male WKY = 382 ± 23; female WKY = 442 ± 11 for proximal right segments) and density (N/mm²; male SHR = 7048 ± 537; female SHR = 10355 ± 359; male WKY = 9457 ± 1437; female WKY = 14351 ± 1448) for proximal right segments) were significantly larger in females of both groups and remarkably larger in WKY than SHR for both genders. Strain and gender differences in phrenic nerve myelinated fiber number are described for the first time in this experimental model of hypertension, indicating the need for thorough functional studies of this nerve in male and female SHR.
Topics: Animals; Female; Male; Myelin Sheath; Nerve Fibers, Myelinated; Phrenic Nerve; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Sex Factors; Species Specificity
PubMed: 21537611
DOI: 10.1590/s0100-879x2011007500053 -
The Tohoku Journal of Experimental... Dec 1988We investigated changes in activities of phrenic nerve (PN) and the recurrent laryngeal nerve (RLN) during progressive hypoxia produced by administration of a mixture of...
We investigated changes in activities of phrenic nerve (PN) and the recurrent laryngeal nerve (RLN) during progressive hypoxia produced by administration of a mixture of 5% O2 in N2 and a mixture of 5% O2 in N2O in 8 vagotomized, paralyzed, and artificially ventilated cats anesthetized with halothane. During progressive hypoxia produced by administration of 5% O2 in N2, both PN and RLN activities initially increased and then decreased at approximately the same rate. The relationship between PN and RLN activities during the respiratory stimulation and the relationship between PN and RLN activities during the depression due to hypoxia were both linear and were represented by the same linear regression line. The responses of PN and RLN activities to progressive hypoxia produced by administration of 5% O2 in N2O were basically similar to those observed during administration of 5% O2 in N2 although a concomitant increase in depth of anesthesia with N2O enhanced the occurrence of hypoxic respiratory depression. These results suggest that the respiratory modulation of recurrent laryngeal motoneuron activity is closely related to that of phrenic motoneuron activity and that both motoneurons share similar control mechanisms. Neither severe hypoxia nor addition of N2O to a halothane-anesthetized cat seems to affect the close linear relationship between PN and RLN activities.
Topics: Animals; Cats; Hypoxia; Laryngeal Nerves; Phrenic Nerve; Recurrent Laryngeal Nerve; Respiration; Vagotomy
PubMed: 3269054
DOI: 10.1620/tjem.156.suppl_57 -
Respiratory Medicine Mar 2013Inspiratory muscle fatigue (IMF) may contribute to the development of exercise limitation and respiratory failure. Identifying fatigue of the inspiratory muscles... (Review)
Review
Inspiratory muscle fatigue (IMF) may contribute to the development of exercise limitation and respiratory failure. Identifying fatigue of the inspiratory muscles requires a rigorous and integrative methodological approach. However, there is no consensus about an optimal protocol to induce and assess the fatigability of the inspiratory muscles. A systematic review was performed to identify, evaluate, and summarize the literature related to the assessment of induced IMF in healthy individuals. The aim was to identify factors that are related consistently to IMF, as well as to suggest possible assessment methods. MEDLINE and EMBASE were searched for relevant articles until February 2012. Only studies with a quantitative description of assessment and outcome were included. The search yielded 460 citations and a total of 77 studies were included. Inspiratory muscle fatigue was produced acutely by inspiratory resistive loading (IRL), whole body exercise (WBE), hyperpnea, or WBE combined with IRL, and under normocapnic, hypoxic or hypercapnic conditions. To detect IMF, most studies (64%) used phrenic nerve stimulation, 44% used a maximal voluntary inspiratory maneuver and the remainder used electromyography. The heterogeneity of the published reports precluded a quantitative analysis. Inspiratory resistive loadings at intensities of 60-80% of maximum, and cycling at 85% of maximum were found to produce IMF most consistently. Hypoxic or hypercapnic conditions, and WBE combined with IRL, exacerbated IMF. The specific outcome measures employed to detect IMF, the magnitude of their change, as well as their functional significance, are ultimately dependent upon the research question being addressed.
Topics: Diaphragm; Electric Stimulation; Exercise Test; Humans; Muscle Fatigue; Phrenic Nerve; Respiratory Muscles
PubMed: 23273596
DOI: 10.1016/j.rmed.2012.11.019