Interactions between respiratory oscillators in adult rats

Breathing in mammals is hypothesized to result from the interaction of two distinct oscillators: the preBötzinger Complex (preBötC) driving inspiration and the lateral parafacial region (pFL) driving active expiration. To understand the interactions between these oscillators, we independently altered their excitability in spontaneously breathing vagotomized urethane-anesthetized adult rats. Hyperpolarizing preBötC neurons decreased inspiratory activity and initiated active expiration, ultimately progressing to apnea, i.e., cessation of both inspiration and active expiration. Depolarizing pFL neurons produced active expiration at rest, but not when inspiratory activity was suppressed by hyperpolarizing preBötC neurons. We conclude that in anesthetized adult rats active expiration is driven by the pFL but requires an additional form of network excitation, i.e., ongoing rhythmic preBötC activity sufficient to drive inspiratory motor output or increased chemosensory drive. The organization of this coupled oscillator system, which is essential for life, may have implications for other neural networks that contain multiple rhythm/pattern generators.

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Actions of specific adenosine receptor A1 and A2 agonists and antagonists in recovery of phrenic motor output following upper cervical spinal cord injury in adult rats

Clinical and Experimental Pharmacology and Physiology ◽

10.1046/j.1440-1681.2002.03750.x ◽

2002 ◽

Vol 29 (10) ◽

pp. 915-923 ◽

Cited By ~ 29

Author(s):

KD Nantwi ◽

HG Goshgarian

Keyword(s):

Spinal Cord ◽

Spinal Cord Injury ◽

Adenosine Receptor ◽

Cervical Spinal Cord ◽

Cervical Spinal Cord Injury ◽

Motor Output ◽

Adult Rats ◽

Cord Injury ◽

Upper Cervical ◽

Adenosine Receptor A1

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Preliminary Evaluation of Artificial Neural Networks as Test Pattern Generators for BIST

2021 36th International Technical Conference on Circuits/Systems, Computers and Communications (ITC-CSCC) ◽

10.1109/itc-cscc52171.2021.9501263 ◽

2021 ◽

Author(s):

Tsutomu Inamoto ◽

Kazuki Ohtomo ◽

Yoshinobu Higami

Keyword(s):

Neural Networks ◽

Artificial Neural Networks ◽

Test Pattern ◽

Preliminary Evaluation ◽

Artificial Neural ◽

Pattern Generators

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Effects of expiratory resistive loading on the sensation of dyspnea

Journal of Applied Physiology ◽

10.1152/jappl.1990.69.1.91 ◽

1990 ◽

Vol 69 (1) ◽

pp. 91-95 ◽

Cited By ~ 16

Author(s):

T. Chonan ◽

M. D. Altose ◽

N. S. Cherniack

Keyword(s):

Control Level ◽

Normal Subjects ◽

Motor Output ◽

Loading Level ◽

Control Frequency ◽

Linear Resistance ◽

Level Ii ◽

Inspiratory Motor ◽

Residual Capacity ◽

Level I

To determine whether an increase in expiratory motor output accentuates the sensation of dyspnea (difficulty in breathing), the following experiments were undertaken. Ten normal subjects, in a series of 2-min trials, breathed freely (level I) or maintained a target tidal volume equal to (level II) or twice the control (level III) at a breathing frequency of 15/min (similar to the control frequency) with an inspiratory load, an expiratory load, and without loads under hyperoxic normocapnia. In tests at levels II and III, end-expiratory lung volume was maintained at functional residual capacity. A linear resistance of 25 cmH2O.1(-1).s was used for both inspiratory and expiratory loading; peak mouth pressure (Pm) was measured, and the intensity of dyspnea (psi) was assessed with a visual analog scale. The sensation of dyspnea increased significantly with the magnitude of expiratory Pm during expiratory loading (level II: Pm = 9.4 +/- 1.5 (SE) cmH2O, psi = 1.26 +/- 0.35; level III: Pm = 20.3 +/- 2.8 cmH2O, psi = 2.22 +/- 0.48) and with inspiratory Pm during inspiratory loading (level II: Pm = 9.7 +/- 1.2 cmH2O, psi = 1.35 +/- 0.38; level III: Pm = 23.9 +/- 3.0 cmH2O, psi = 2.69 +/- 0.60). However, at each level of breathing, neither the intensity of dyspnea nor the magnitude of peak Pm during loading was different between inspiratory and expiratory loading. The augmentation of dyspnea during expiratory loading was not explained simply by increases in inspiratory activity. The results indicate that heightened expiratory as well as inspiratory motor output causes comparable increases in the sensation of difficulty in breathing.

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Control of ventilation in adult rats hypoxic in the neonatal period

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.1990.259.4.r836 ◽

1990 ◽

Vol 259 (4) ◽

pp. R836-R841 ◽

Cited By ~ 24

Author(s):

S. Okubo ◽

J. P. Mortola

Keyword(s):

Neonatal Period ◽

Ventilatory Response ◽

Acute Hypoxia ◽

Lower Sensitivity ◽

Adult Rats ◽

Genetic Characteristics ◽

Ventilatory Responses ◽

Central Inhibition ◽

Inspiratory Activity ◽

High Altitude Natives

Three groups of 50-day-old (i.e., postpuberty) rats have been studied: controls, rats exposed to 6 days of hypoxia [inspired fraction of O2 (FIo2) = 10% O2] when newborn (Nb-Hypox), and rats exposed to the same level and duration of hypoxia after weaning (Ad-Hypox). Ventilation during normoxic breathing was higher in Nb-Hypox than in controls or Ad-Hypox. The ventilatory response to acute hypoxia (10 min of 10% O2) was about one-half in Nb-Hypox than in the other two groups. Additional measurements performed on Nb-Hypox and controls showed minimal or no differences between the two groups in the ventilatory responses to hyperoxia and hypercapnia, heart rate and blood pressure at various FIO2, and blood biochemistry. Analysis of the Hering-Breuer reflexes, during barbiturate anesthesia, suggested a decreased central inhibition on inspiratory activity in Nb-Hypox, which with a lower sensitivity to inputs from the peripheral chemoreceptors may contribute to the normoxic hyperventilation and the blunted response to acute hypoxia. The ventilatory patterns of Nb-Hypox rats bear numerous similarities with those of high-altitude natives and could suggest that the highlander's ventilatory responses are not genetic characteristics but relate to chronic hypoxia early in life.

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Intra- and intersegmental influences among central pattern generating networks in the walking system of the stick insect

Journal of Neurophysiology ◽

10.1152/jn.00321.2017 ◽

2017 ◽

Vol 118 (4) ◽

pp. 2296-2310 ◽

Cited By ~ 22

Author(s):

Charalampos Mantziaris ◽

Till Bockemühl ◽

Philip Holmes ◽

Anke Borgmann ◽

Silvia Daun ◽

...

Keyword(s):

Neural Networks ◽

Sensory Feedback ◽

Muscarinic Acetylcholine Receptor ◽

Central Pattern Generators ◽

Sensory Information ◽

Direct Interaction ◽

Stick Insect ◽

Weakly Coupled ◽

The Neural Networks ◽

Pattern Generators

To efficiently move around, animals need to coordinate their limbs. Proper, context-dependent coupling among the neural networks underlying leg movement is necessary for generating intersegmental coordination. In the slow-walking stick insect, local sensory information is very important for shaping coordination. However, central coupling mechanisms among segmental central pattern generators (CPGs) may also contribute to this. Here, we analyzed the interactions between contralateral networks that drive the depressor trochanteris muscle of the legs in both isolated and interconnected deafferented thoracic ganglia of the stick insect on application of pilocarpine, a muscarinic acetylcholine receptor agonist. Our results show that depressor CPG activity is only weakly coupled between all segments. Intrasegmental phase relationships differ between the three isolated ganglia, and they are modified and stabilized when ganglia are interconnected. However, the coordination patterns that emerge do not resemble those observed during walking. Our findings are in line with recent studies and highlight the influence of sensory input on coordination in slowly walking insects. Finally, as a direct interaction between depressor CPG networks and contralateral motoneurons could not be observed, we hypothesize that coupling is based on interactions at the level of CPG interneurons. NEW & NOTEWORTHY Maintaining functional interleg coordination is vitally important as animals locomote through changing environments. The relative importance of central mechanisms vs. sensory feedback in this process is not well understood. We analyzed coordination among the neural networks generating leg movements in stick insect preparations lacking phasic sensory feedback. Under these conditions, the networks governing different legs were only weakly coupled. In stick insect, central connections alone are thus insufficient to produce the leg coordination observed behaviorally.

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Medullary neurons mediating the inhibition of inspiration by intercostal muscle tendon organs?

Journal of Applied Physiology ◽

10.1152/jappl.1988.65.6.2498 ◽

1988 ◽

Vol 65 (6) ◽

pp. 2498-2505 ◽

Cited By ~ 9

Author(s):

R. Shannon ◽

D. C. Bolser ◽

B. G. Lindsey

Keyword(s):

Respiratory Neurons ◽

Neuron Activity ◽

Intercostal Muscle ◽

Group I ◽

Afferent Fibers ◽

Inspiratory Neuron ◽

Inspiratory Activity ◽

Tendon Organs ◽

Retrofacial Nucleus ◽

Spontaneously Breathing

Studies were conducted to test the hypothesis that nonrespiratory-modulated units are last-order interneurons mediating the effects of intercostal muscle tendon organs on medullary inspiratory neuron activity. Vagotomized, anesthetized, or decerebrate cats were used. Results show the following. 1) Afferents from different receptor types (i.e., intercostal tendon organs and chest wall cutaneous receptors) that inhibit medullary inspiratory neuron activities evoke the same units. 2) Gastrocnemius muscle group I afferent fibers evoke some of the same units as intercostal afferents but do not alter respiratory activity. 3) The "pneumotaxic center" and laryngeal nerve afferents, which inhibit medullary inspiratory activity, evoke different medullary units than intercostal afferents. 4) Evoked units are not active in spontaneously breathing cats. Additional results suggest that a few respiratory neurons near the retrofacial nucleus may be involved in the mediation of the inspiratory inhibitory effects of intercostal tendon organs. These results do not establish the mechanism by which intercostal muscle tendon organs reduces medullary inspiratory activity.

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Altered Gravity Highlights Central Pattern Generator Mechanisms

Journal of Neurophysiology ◽

10.1152/jn.90436.2008 ◽

2008 ◽

Vol 100 (5) ◽

pp. 2819-2824 ◽

Cited By ~ 32

Author(s):

Olivier White ◽

Yannick Bleyenheuft ◽

Renaud Ronsse ◽

Allan M. Smith ◽

Jean-Louis Thonnard ◽

...

Keyword(s):

Neural Networks ◽

Resonant Frequency ◽

Parabolic Flight ◽

Central Pattern Generators ◽

Arm Movement ◽

Rhythmic Movements ◽

Earth Environment ◽

Major Interest ◽

Microgravity Conditions ◽

Pattern Generators

In many nonprimate species, rhythmic patterns of activity such as locomotion or respiration are generated by neural networks at the spinal level. These neural networks are called central pattern generators (CPGs). Under normal gravitational conditions, the energy efficiency and the robustness of human rhythmic movements are due to the ability of CPGs to drive the system at a pace close to its resonant frequency. This property can be compared with oscillators running at resonant frequency, for which the energy is optimally exchanged with the environment. However, the ability of the CPG to adapt the frequency of rhythmic movements to new gravitational conditions has never been studied. We show here that the frequency of a rhythmic movement of the upper limb is systematically influenced by the different gravitational conditions created in parabolic flight. The period of the arm movement is shortened with increasing gravity levels. In weightlessness, however, the period is more dependent on instructions given to the participants, suggesting a decreased influence of resonant frequency. Our results are in agreement with a computational model of a CPG coupled to a simple pendulum under the control of gravity. We demonstrate that the innate modulation of rhythmic movements by CPGs is highly flexible across gravitational contexts. This further supports the involvement of CPG mechanisms in the achievement of efficient rhythmic arm movements. Our contribution is of major interest for the study of human rhythmic activities, both in a normal Earth environment and during microgravity conditions in space.

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Do canine scalene and sternomastoid muscles play a role in breathing?

Journal of Applied Physiology ◽

10.1152/jappl.1994.76.1.242 ◽

1994 ◽

Vol 76 (1) ◽

pp. 242-252 ◽

Cited By ~ 21

Author(s):

A. De Troyer ◽

M. Cappello ◽

J. F. Brichant

Keyword(s):

Respiratory Function ◽

Respiratory Drive ◽

Airway Occlusion ◽

Single Breath ◽

Large Numbers ◽

Inspiratory Resistance ◽

Cervical Vagotomy ◽

Inspiratory Activity ◽

Unanesthetized Animals ◽

Spontaneously Breathing

To assess the respiratory function of the scalene and sternomastoid muscles in the dog, we studied the effect of graded increases in inspiratory airflow resistance and single-breath airway occlusion on the electrical activity of these muscles in 18 supine anesthetized spontaneously breathing animals. The sternomastoids never showed any activity, and the scalenes showed some inspiratory activity during occlusion in only two animals. The adoption of the prone position and bilateral cervical vagotomy did not affect this pattern. Hypercapnia also did not elicit any sternomastoid activity and induced scalene inspiratory activity during occlusion in only four of nine animals. On microscopic examination, however, both muscles were found to contain large numbers of spindles, suggesting that they have the capacity to respond to stretch. In addition, with increases in inspiratory resistance, both the sternum and ribs were displaced in the caudal direction. As a result, the scalenes demonstrated a gradual inspiratory lengthening and the normal inspiratory lengthening of the sternomastoids was accentuated. Additional studies in three unanesthetized animals showed consistent activity in the scalene and sternomastoid muscles during movements of the trunk and neck but no activity during breathing, including occluded breathing. These observations thus indicate that the alpha-motoneurons of the scalene and sternomastoid muscles in the dog have very small central respiratory drive potentials with respect to their critical firing threshold. In this animal, these muscles do not have a significant respiratory function.

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