scholarly journals Diaphragm neuromuscular transmission failure in aged rats

2019 ◽  
Vol 122 (1) ◽  
pp. 93-104 ◽  
Author(s):  
Matthew J. Fogarty ◽  
Maria A. Gonzalez Porras ◽  
Carlos B. Mantilla ◽  
Gary C. Sieck
Keyword(s):  
Nerve Stimulation ◽  
Phrenic Nerve ◽  
Neuromuscular Transmission ◽  
Motor Units ◽  
Diaphragm Muscle ◽  
Muscle Stimulation ◽  
Transmission Failure ◽  
Old Rats ◽  
Motor Neuron Loss ◽  
Fast Twitch

In aging Fischer 344 rats, phrenic motor neuron loss, neuromuscular junction abnormalities, and diaphragm muscle (DIAm) sarcopenia are present by 24 mo of age, with larger fast-twitch fatigue-intermediate (type FInt) and fast-twitch fatigable (type FF) motor units particularly vulnerable. We hypothesize that in old rats, DIAm neuromuscular transmission deficits are specific to type FInt and/or FF units. In phrenic nerve/DIAm preparations from rats at 6 and 24 mo of age, the phrenic nerve was supramaximally stimulated at 10, 40, or 75 Hz. Every 15 s, the DIAm was directly stimulated, and the difference in forces evoked by nerve and muscle stimulation was used to estimate neuromuscular transmission failure. Neuromuscular transmission failure in the DIAm was observed at each stimulation frequency. In the initial stimulus trains, the forces evoked by phrenic nerve stimulation at 40 and 75 Hz were significantly less than those evoked by direct muscle stimulation, and this difference was markedly greater in 24-mo-old rats. During repetitive nerve stimulation, neuromuscular transmission failure at 40 and 75 Hz worsened to a greater extent in 24-mo-old rats compared with younger animals. Because type IIx and/or IIb DIAm fibers (type FInt and/or FF motor units) display greater susceptibility to neuromuscular transmission failure at higher frequencies of stimulation, these data suggest that the age-related loss of larger phrenic motor neurons impacts nerve conduction to muscle at higher frequencies and may contribute to DIAm sarcopenia in old rats. NEW & NOTEWORTHY Diaphragm muscle (DIAm) sarcopenia, phrenic motor neuron loss, and perturbations of neuromuscular junctions (NMJs) are well described in aged rodents and selectively affect FInt and FF motor units. Less attention has been paid to the motor unit-specific aspects of nerve-muscle conduction. In old rats, increased neuromuscular transmission failure occurred at stimulation frequencies where FInt and FF motor units exhibit conduction failures, along with decreased apposition of pre- and postsynaptic domains of DIAm NMJs of these units.

scholarly journals Diaphragm Neuromuscular Transmission Failure in a Mouse Model of an Early-Onset Neuromotor Disorder

2020 ◽  
Author(s):  
Matthew J. Fogarty ◽  
Joline E. Brandenburg ◽  
Gary C. Sieck
Keyword(s):  
Motor Neurons ◽  
Nerve Stimulation ◽  
Phrenic Nerve ◽  
Early Onset ◽  
Neuromuscular Transmission ◽  
Postnatal Period ◽  
Diaphragm Muscle ◽  
Phrenic Nerve Stimulation ◽  
Transmission Failure ◽  
S Period

The spa transgenic mouse displays spasticity and hypertonia that develops during the early postnatal period, with motor impairments that are remarkably similar to symptoms of human cerebral palsy. Previously, we observed that spa mice have fewer phrenic motor neurons innervating the diaphragm muscle (DIAm). We hypothesize that spa mice exhibit increased susceptibility to neuromuscular transmission failure (NMTF) due to an expanded innervation ratio. We retrogradely-labeled phrenic motor neurons with rhodamine and imaged them in horizontal sections (70 µm) using confocal microscopy. Phrenic nerve-DIAm strip preparations from wildtype and spa mice were stretched to optimal length, and force was evoked by phrenic nerve stimulation at 10, 40 or 75 Hz in 330 ms duration trains repeated each s (33% duty cycle) across a 120 s period. To assess NMTF, force evoked by phrenic nerve stimulation was compared to force evoked by direct DIAm stimulation superimposed every 15 s. Total DIAm fiber number was estimated in hematoxylin and eosin stained strips. Compared to wildtype, spa mice had over two-fold greater NMTF during the first stimulus train that persisted throughout the 120 s period of repetitive activation. In both wildtype and spa mice, NMTF was stimulation-frequency dependent. There was no difference in neuromuscular junction morphology or the total number of DIAm fibers between wildtype and spa mice, however there was an increase innervation ratio (39%) in spa mice. We conclude that early-onset developmental neuromotor disorders impair the efficacy of DIAm neuromuscular transmission, likely to contribute to respiratory complications.

Effect of hypoxia on neuromuscular transmission in the developing diaphragm

1994 ◽  
Vol 76 (2) ◽  
pp. 708-713 ◽  
Author(s):  
A. R. Bazzy
Keyword(s):  
Nerve Stimulation ◽  
Phrenic Nerve ◽  
Neuromuscular Transmission ◽  
Ringer Solution ◽  
Diaphragm Muscle ◽  
Control Force ◽  
Force Response ◽  
Direct Stimulation ◽  
Frequency Of Stimulation ◽  
Predominant Effect

To study the effects of hypoxia on neuromuscular transmission in the developing diaphragm, phrenic nerve-hemidiaphragm preparations were obtained from newborn (4–9 days) and older (22–30 days) rats. Diaphragms were stimulated directly or indirectly (via the nerve) for 1 s at frequencies of 10–80 Hz. Force generated in response to stimulation was measured during perfusion of oxygenated Ringer solution (control) and Ringer solution bubbled with 95% N2–5% CO2 (hypoxia). After 45 min of hypoxia, the force response of the older diaphragms to direct stimulation had decreased to approximately 50% of control at > or = 40 Hz; however, when stimulation occurred via the nerve at these frequencies only 15–20% of control force was generated. In the newborn diaphragms, the force decrement after similar or longer periods of hypoxia (< or = 90 min) was 30– 40% irrespective of the route or frequency of stimulation. After 15 min of reoxygenation, the force response to both muscle and nerve stimulation recovered completely in the older diaphragms but only partially in the newborn diaphragms (range 77% of control at 50 Hz to 95% of control at 10 Hz). These data suggest that in the newborn diaphragm 1) neuromuscular transmission is more resistant to the effects of hypoxia than the older diaphragm and 2) the predominant effect of hypoxia is peripheral in the diaphragm muscle fibers, whereas in the older diaphragm the effect is before or at the neuromuscular junction.

Developmental changes in neuromuscular transmission in the rat diaphragm

1991 ◽  
Vol 71 (1) ◽  
pp. 280-286 ◽  
Author(s):  
J. D. Feldman ◽  
A. R. Bazzy ◽  
T. R. Cummins ◽  
G. G. Haddad
Keyword(s):  
Phrenic Nerve ◽  
Neuromuscular Transmission ◽  
Peak Force ◽  
Neonatal Rat ◽  
Maximum Force ◽  
Muscle Stimulation ◽  
Rat Diaphragm ◽  
Stimulus Train ◽  
Old Rats

Neuromuscular transmission was studied in diaphragms from rats of three ages, 4–7 days old, 11–12 days old, and adults with the use of an in vitro phrenic nerve-hemidiaphragm preparation. Each hemidiaphragm was stimulated via either muscle or nerve with 1-s stimulus trains at frequencies from 10 to 100 Hz. The patterns of force development obtained in response to the two routes of stimulation were compared for each group. Diaphragms from adults developed maximum force in response to stimulation of approximately 40 Hz with no significant decrease in force at higher frequencies. Within each stimulus train, once peak force was achieved, it was maintained for the remainder of the stimulus and responses to nerve and muscle stimulation were almost identical. In contrast, diaphragms from 4- to 7-day-old rats developed maximum force at approximately 20 Hz; stimulation at greater than or equal to 60 Hz induced significantly less peak force. This decrease in peak force at higher frequencies was significantly larger for nerve than for muscle stimulation. In addition, during each nerve stimulus train diaphragms from 4- to 7-day-old rats were unable to maintain peak force, which decreased at frequencies greater than 20 Hz. The decrease in force reached approximately 50% of peak at stimulation frequencies greater than or equal to 60 Hz. Diaphragms from 11- to 12-day-old rats showed intermediate responses. Based on the responses to phrenic nerve stimulation, we conclude that the neonatal rat diaphragm shows marked neuromuscular transmission failure that is not seen in the adult.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Exogenous testosterone treatment decreases diaphragm neuromuscular transmission failure in male rats

2001 ◽  
Vol 90 (3) ◽  
pp. 850-856 ◽  
Author(s):  
Cesar E. Blanco ◽  
Wen-Zhi Zhan ◽  
Yun-Hua Fang ◽  
Gary C. Sieck
Keyword(s):  
Nerve Stimulation ◽  
Neuromuscular Transmission ◽  
Fiber Type ◽  
Male Rats ◽  
Control Group ◽  
Muscle Stimulation ◽  
Type I ◽  
Glycogen Depletion ◽  
Testosterone Treatment ◽  
Transmission Failure

The effect of chronic exogenous testosterone (T) treatment on neuromuscular transmission in the diaphragm (Dia) muscle of adult male rats was determined. The contribution of neuromuscular transmission failure (NTF) to Dia fatigue was evaluated by superimposing intermittent direct muscle stimulation on repetitive nerve stimulation of isometric contraction in vitro. T treatment significantly reduced the contribution of NTF to Dia fatigue by ∼20% ( P < 0.001). Fiber type-specific effects on NTF were determined by measuring Dia fiber glycogen levels subsequent to repetitive nerve or muscle stimulation. T treatment had no effect on glycogen depletion in Dia type I and IIa fibers regardless of stimulation route. In the control group, type IIx fibers demonstrated significantly less glycogen depletion after nerve stimulation compared with direct muscle stimulation ( P < 0.05), suggesting the presence of NTF. In contrast, T treatment increased glycogen depletion of type IIx fibers during nerve stimulation to levels similar to those after direct muscle stimulation. These data indicate that testosterone treatment substantially improves neuromuscular transmission in the Dia.

Differential susceptibility of diaphragm muscle fibers to neuromuscular transmission failure

1993 ◽  
Vol 75 (1) ◽  
pp. 341-348 ◽  
Author(s):  
B. D. Johnson ◽  
G. C. Sieck
Keyword(s):  
Muscle Fiber ◽  
Nerve Stimulation ◽  
Neuromuscular Transmission ◽  
Rank Order ◽  
Diaphragm Muscle ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Glycogen Depletion ◽  
Stimulation Rate ◽  
Transmission Failure

The pattern of glycogen utilization was used to determine whether various muscle fiber types in the rat diaphragm are differentially susceptible to neuromuscular transmission failure. Muscle segments from the midcostal region were repetitively stimulated directly or via the phrenic nerve at 10 or 75 Hz. Muscle fiber types were classified histochemically as type I, IIa, or IIb. The amount of muscle fiber glycogen depletion with direct stimulation depended on stimulation rate (75 Hz > 10 Hz) and fiber type (IIb > IIa > I). However, with nerve stimulation, muscle fiber glycogen depletion did not display the same dependency on stimulation rate (10 Hz > 75 Hz), although with stimulation at 10 Hz, the same rank order of fiber depletion was observed (IIb > IIa > I). This rank order of depletion was reversed (I > IIa > IIb) during repetitive stimulation of the nerve at 75 Hz. By intermittently stimulating the muscle directly during continuous nerve stimulation, we determined that neuromuscular transmission failure contributed significantly to the force decline after 2 min of stimulation at 75 Hz but relatively little to the force decline after 2 min of stimulation at 10 Hz. A significantly greater fraction of the force decline could be attributed to neuromuscular transmission failure with repetitive bouts of stimulation at 10 Hz. We conclude that neuromuscular transmission failure causes a significant portion of the force decline after 8 min of stimulation at 10 and 75 Hz, that all diaphragm fiber types are susceptible to neuromuscular transmission failure, but that type IIb fibers are particularly susceptible at higher frequencies of stimulation.

scholarly journals Diaphragm curvature modulates the relationship between muscle shortening and volume displacement

2011 ◽  
Vol 301 (1) ◽  
pp. R76-R82 ◽  
Author(s):  
Brad J. Greybeck ◽  
Matthew Wettergreen ◽  
Rolf D. Hubmayr ◽  
Aladin M. Boriek
Keyword(s):  
Nerve Stimulation ◽  
Phrenic Nerve ◽  
Spontaneous Breathing ◽  
Three Dimensional ◽  
Diaphragm Muscle ◽  
Phrenic Nerve Stimulation ◽  
Lung Volumes ◽  
Muscle Shortening ◽  
Residual Capacity ◽  
The Relationship

During physiological spontaneous breathing maneuvers, the diaphragm displaces volume while maintaining curvature. However, with maximal diaphragm activation, curvature decreases sharply. We tested the hypotheses that the relationship between diaphragm muscle shortening and volume displacement (VD) is nonlinear and that curvature is a determinant of such a relationship. Radiopaque markers were surgically placed on three neighboring muscle fibers in the midcostal region of the diaphragm in six dogs. The three-dimensional locations were determined using biplanar fluoroscopy and diaphragm VD, curvature, and muscle shortening were computed in the prone and supine postures during spontaneous breathing (SB), spontaneous inspiration efforts after airway occlusion at lung volumes ranging from functional residual capacity (FRC) to total lung capacity, and during bilateral maximal phrenic nerve stimulation at those same lung volumes. In supine dogs, diaphragm VD was approximately two- to three-fold greater during maximal phrenic nerve stimulation than during SB. The contribution of muscle shortening to VD nonlinearly increases with level of diaphragm activation independent of posture. During submaximal diaphragm activation, the contribution is essentially linear due to constancy of diaphragm curvature in both the prone and supine posture. However, the sudden loss of curvature during maximal bilateral phrenic nerve stimulation at muscle shortening values greater than 40% (ΔL/LFRC) causes a nonlinear increase in the contribution of muscle shortening to diaphragm VD, which is concomitant with a nonlinear change in diaphragm curvature. We conclude that the nonlinear relationship between diaphragm muscle shortening and its VD is, in part, due to a loss of its curvature at extreme muscle shortening.

Diaphragmatic failure during loaded breathing: role of neuromuscular transmission

1993 ◽  
Vol 74 (4) ◽  
pp. 1679-1683 ◽  
Author(s):  
A. R. Bazzy ◽  
D. F. Donnelly
Keyword(s):  
Phrenic Nerve ◽  
Neuromuscular Transmission ◽  
Diaphragm Muscle ◽  
Plateau Phase ◽  
Nerve Activity ◽  
Transdiaphragmatic Pressure ◽  
M Wave ◽  
Arterial Pco2 ◽  
Loaded Breathing

To determine whether central or peripheral mechanisms are responsible for diaphragmatic failure during loaded breathing, phrenic nerve activity (iENG), diaphragm muscle electromyogram (iEMG), and transdiaphragmatic pressure (Pdi) were measured in unanesthetized chronically instrumented sheep during inspiratory flow-resistive (IFR) loaded breathing. After placement of the IFR load, Pdi increased initially and remained relatively stable for 10–30 min [Pdi = 69.9 +/- 6.3 (SE) cmH2O, n = 6]; arterial PCO2 also increased from baseline (35.8 +/- 0.9 Torr) to 55.1 +/- 4.7 Torr. During IFR loading, iEMG and iENG also increased from baseline, but during the plateau phase of Pdi, iENG continued to increase at the same time while iEMG was stable, and the M wave, evoked by phrenic nerve stimulation, decreased during this period. After the plateau phase, Pdi decreased and arterial PCO2 increased, at which point the study was terminated (at 82.1 +/- 20.6 min). The observation that iENG increased while Pdi and iEMG were stable demonstrates a reduced efficiency of neuromuscular transmission and suggests that the neuromuscular junction is an important site of diaphragmatic failure in unanesthetized sheep during IFR loaded breathing.

Relative contribution of neurotransmission failure to diaphragm fatigue

1990 ◽  
Vol 68 (1) ◽  
pp. 174-180 ◽  
Author(s):  
J. H. Kuei ◽  
R. Shadmehr ◽  
G. C. Sieck
Keyword(s):  
Nerve Stimulation ◽  
Phrenic Nerve ◽  
Neural Stimulation ◽  
Muscle Stimulation ◽  
Phrenic Nerve Stimulation ◽  
Relative Contribution ◽  
The Difference ◽  
Second Procedure ◽  
Phrenic Stimulation ◽  
Diaphragm Fatigue

Two procedures were used to estimate the relative contribution of neurotransmission failure (NF) to fatigue of the rat diaphragm at different rates of phrenic nerve stimulation. In one, direct muscle stimulation was intermittently superimposed on neural stimulation of the diaphragm, and the relative contribution of NF was estimated by the difference in generated tension. In a second procedure, diaphragm fatigue was induced by using either direct muscle stimulation (with complete blockade of the neuromuscular junction by d-tubocurare) or phrenic nerve stimulation. The relative contribution of NF to diaphragm fatigue was then estimated by comparing the force loss during these two modes of stimulation. With both procedures, it was observed that 1) the relative contribution of NF to diaphragm fatigue was less than 45% at each frequency of phrenic nerve stimulation; 2) the relative contribution of NF to diaphragm fatigue increased at higher rates of phrenic stimulation, reaching a maximum at 75 pulses/s; and 3) the relative contribution of NF to diaphragm fatigue reached a plateau after 2 min of repetitive stimulation.

Phrenic nerve-diaphragm preparations in relation to temperature and hibernation

1961 ◽  
Vol 200 (3) ◽  
pp. 565-571 ◽  
Author(s):  
Frank E. South
Keyword(s):  
Mechanical Properties ◽  
Neuromuscular Blockade ◽  
Phrenic Nerve ◽  
Neuromuscular Transmission ◽  
Incubation Temperature ◽  
Diaphragm Muscle ◽  
Muscle Tissues ◽  
Contraction And Relaxation ◽  
Incubation Temperatures ◽  
And Control

Electrical and mechanical properties, as correlates of incubation temperature, of phrenic nerve-diaphragm preparations obtained from hibernating and control hamsters and from rats were examined. Six incubation temperatures, ranging from 5° to 38°C, were used. Nerves of rats evidenced much steeper temperature functions than did either hamster group, with respect to irritability, spike voltage and conduction velocity such that they were inexcitable at 5°C. The hibernating and control hamster groups behaved quite similarly to each other in these respects. Neuromuscular blockade occurred at 10°C in the rat preparations and at 5°C of the control hamster preparations but in no case did it occur among those of hibernating animals. Similar or analogous differences were apparent in diaphragm muscle tissues insofar as irritability, tension production and rates of contraction and relaxation are concerned. These observations were taken to demonstrate the existence of phylogenetic adaptations correlated with the ability of hamsters to hibernate as well as the probable necessity for a prehibernal acclimatization of such mechanisms as neuromuscular transmission on the part of these animals.

scholarly journals Chronic hypoxia modulates diaphragm function in the developing rat

2001 ◽  
Vol 90 (6) ◽  
pp. 2325-2329 ◽  
Author(s):  
L. J. Kass ◽  
A. R. Bazzy
Keyword(s):  
Relaxation Time ◽  
Nerve Stimulation ◽  
Neuromuscular Transmission ◽  
Chronic Hypoxia ◽  
Specific Force ◽  
Contraction Time ◽  
Old Rats ◽  
Delayed Maturation ◽  
And Control ◽  
Developing Rat

We studied the effect of chronic hypoxia on contractile properties and neuromuscular transmission in the developing rat diaphragm. We hypothesized that chronic hypoxia delays maturation of neuromuscular transmission. Phrenic nerve hemidiaphragm preparations were harvested from 3- to 26-day-old rats and littermates raised in 9.5% oxygen. Specific force, contraction time, and one-half relaxation time were measured. Each diaphragm was stimulated directly or via its nerve with 1-s trains at 10–100 Hz. Contraction time and one-half relaxation time decreased with advancing age in both groups, with a greater rate of decrease in hypoxic diaphragms. Specific force was lower for hypoxic diaphragms compared with controls. Diaphragms from the 3- to 10-day-old control and hypoxic groups generated less force in response to stimulation at frequencies >40 Hz but did so to a greater degree with nerve stimulation. Nerve stimulation of diaphragms from 11- to 18-day-old hypoxic rats showed a greater decrease in force with increasing frequency compared with age-matched controls. Diaphragms from 19- to 26-day-old rats showed no difference between the hypoxic and control groups. We conclude that chronic hypoxia leads to diaphragms that generate lower specific force as well as to a delayed maturation of mechanisms involved in neuromuscular transmission.

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