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

1988 ◽  
Vol 65 (6) ◽  
pp. 2498-2505 ◽  
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.

scholarly journals Midline section of the medulla abolishes inspiratory activity and desynchronizes pre-inspiratory neuron rhythm on both sides of the medulla in newborn rats

2015 ◽  
Vol 113 (7) ◽  
pp. 2871-2878 ◽  
Author(s):  
Hiroshi Onimaru ◽  
Kayo Tsuzawa ◽  
Yoshimi Nakazono ◽  
Wiktor A. Janczewski
Keyword(s):  
Facial Nerve ◽  
Respiratory Rhythm ◽  
Root Activity ◽  
Respiratory Neurons ◽  
Neuron Activity ◽  
Newborn Rats ◽  
Inspiratory Neuron ◽  
Inspiratory Activity ◽  
Old Rats ◽  
Parafacial Respiratory Group

Each half of the medulla contains respiratory neurons that constitute two generators that control respiratory rhythm. One generator consists of the inspiratory neurons in the pre-Bötzinger complex (preBötC); the other, the pre-inspiratory (Pre-I) neurons in the parafacial respiratory group (pFRG), rostral to the preBötC. We investigated the contribution of the commissural fibers, connecting the respiratory rhythm generators located on the opposite side of the medulla to the generation of respiratory activity in brain stem-spinal cord preparation from 0- to 1-day-old rats. Pre-I neuron activity and the facial nerve and/or first lumbar (L1) root activity were recorded as indicators of the pFRG-driven rhythm. Fourth cervical ventral root (C4) root and/or hypoglossal (XII) nerve activity were recorded as indicators of preBötC-driven inspiratory activity. We found that a midline section that interrupted crossed fibers rostral to the obex irreversibly eliminated C4 and XII root activity, whereas the Pre-I neurons, facial nerve, and L1 roots remained rhythmically active. The facial and contralateral L1 nerve activities were synchronous, whereas right and left facial (and right and left L1) nerves lost synchrony. Optical recordings demonstrated that pFRG-driven burst activity was preserved after a midline section, whereas the preBötC neurons were no longer rhythmic. We conclude that in newborn rats, crossed excitatory interactions (via commissural fibers) are necessary for the generation of inspiratory bursts but not for the generation of rhythmic Pre-I neuron activity.

Synaptic effects of intercostal tendon organs on membrane potentials of medullary respiratory neurons

1989 ◽  
Vol 61 (5) ◽  
pp. 918-926 ◽  
Author(s):  
D. C. Bolser ◽  
J. E. Remmers
Keyword(s):  
Membrane Potentials ◽  
Stage I ◽  
Respiratory Cycle ◽  
Respiratory Neurons ◽  
Neuron Activity ◽  
Afferent Pathway ◽  
Medullary Respiratory Neurons ◽  
Inspiratory Neurons ◽  
Inspiratory Neuron ◽  
Tendon Organs

1. Stimulation of intercostal muscle tendon organs or their afferent fibers reduces medullary inspiratory neuron activity, decreases motor output to inspiratory muscles, and increases the activity of expiratory laryngeal motoneurons. The present study examines the synaptic mechanisms underlying these changes to obtain information about medullary neurons that participate in the afferent limb of this reflex pathway. 2. Membrane potentials of medullary respiratory neurons were recorded in decerebrate paralyzed cats. Postsynaptic potentials (PSPs) elicited in these neurons by intercostal nerve stimulation (INS) were compared before and after intracellular iontophoresis of chloride ions. After chloride injection, the normal hyperpolarization caused by inhibitory (I) PSPs is "reversed" to depolarization. 3. In inspiratory neurons, reversal of IPSPs by chloride injection also reversed hyperpolarization produced by INS when applied during any portion of the respiratory cycle. This observation suggests that increased chloride conductance of the postsynaptic membrane mediated the inhibition. Further, it is very likely that the last-order interneuron in the afferent pathway must be excited by INS and alter inspiratory neuron activity via an inhibitory synapse. The linear relationship between the amplitude of the INS induced PSP and membrane potential of inspiratory neurons provided evidence that neurons in the afferent pathway are not respiratory modulated. 4. The membranes of expiratory vagal motoneurons and post-inspiratory neurons were depolarized by INS during all portions of the respiratory cycle before IPSP reversal. Reversal of IPSPs affected neither this depolarization of expiratory vagal motoneurons during stage I and II expiration nor that of post-inspiratory neurons during stage I expiration. Thus this depolarization probably resulted from synaptic excitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Muscle afferents and activity of respiratory neurons

1961 ◽  
Vol 200 (4) ◽  
pp. 679-684 ◽  
Author(s):  
K. Koizumi ◽  
J. Ushiyama ◽  
C. McC. Brooks
Keyword(s):  
Muscle Afferents ◽  
Monosynaptic Reflex ◽  
Respiratory Neurons ◽  
Group I ◽  
Afferent Fibers ◽  
Intercostal Nerves ◽  
Polysynaptic Reflexes ◽  
Root Stimulation ◽  
Mixed Nerve ◽  
Stimulation Of

Respiratory effects of stimulating afferent fibers of muscle, skin and mixed nerve were determined in Nembutal-anesthetized cats. Repetitive stimuli which produced only monosynaptic reflex actions caused augmentation of respiration. When stronger stimuli also activated fibers of a smaller diameter than group I afferents, polysynaptic reflexes were evoked and greater changes in respiration resulted. Volume rather than rate changes were induced by stimulation of these muscle afferents. Microelectrodes were used to record from respiratory neurons of the medulla and pons. Most neurons fired in conjunction with inspiration; stimulation of muscle afferents advanced time of firing and increased frequency of discharge. Neurons firing in conjunction with expiration were inhibited by muscle afferents. A few neurons of the pons showed respiration-linked activity modified by afferent nerve stimulation. Segmental reflex discharges, out intercostal nerves, elicited by dorsal root stimulation were found to be inhibited by stimulation of muscle afferents. Discharges from muscle receptors affect ventilatory volumes and activities of medullary neurons which seemingly participate in the control of respiration.

Medullary expiratory activity: influence of intercostal tendon organs and muscle spindle endings

1987 ◽  
Vol 62 (3) ◽  
pp. 1057-1062 ◽  
Author(s):  
R. Shannon ◽  
D. C. Bolser ◽  
B. G. Lindsey
Keyword(s):  
Muscle Spindle ◽  
Inhibitory Effect ◽  
Neuron Activity ◽  
Abdominal Muscles ◽  
Intercostal Muscle ◽  
Excitatory Effect ◽  
Expiratory Neurons ◽  
Motoneuron Activity ◽  
Tendon Organs ◽  
Muscle Spindle Endings

Studies were conducted to determine the effects of intercostal muscle spindle endings (MSEs) and tendon organs (TOs) on medullary expiratory activity in decerebrate cats. Impeded intercostal muscle contractions, elicited by electrical stimulation of the peripheral cut end of the T6 ventral root, were used to stimulate intercostal TOs without MSEs. Impeded contractions of the intercostal muscles augmented expiratory laryngeal motoneuron activity, and either had no effect on or reduced the activity of bulbospinal expiratory neurons. Vibration was used to stimulate intercostal MSEs. Intercostal MSEs had no effect on medullary expiratory neuron activity. It is concluded that both external and internal intercostal TOs have an excitatory effect on expiratory laryngeal motoneuron activity and an inhibitory effect on a subpopulation of expiratory neurons driving intercostal and/or abdominal muscles, and intercostal MSEs have no direct influence on medullary expiratory activity.

Medullary inspiratory activity: influence of intercostal tendon organs and muscle spindle endings

1987 ◽  
Vol 62 (3) ◽  
pp. 1046-1056 ◽  
Author(s):  
D. C. Bolser ◽  
B. G. Lindsey ◽  
R. Shannon
Keyword(s):  
Electrical Stimulation ◽  
Muscle Spindle ◽  
Inhibitory Effect ◽  
Muscle Contractions ◽  
Ventral Root ◽  
Intercostal Muscle ◽  
Inspiratory Activity ◽  
Tendon Organs ◽  
Muscle Spindle Endings ◽  
Stimulation Of

Studies were conducted to determine the effects of intercostal muscle spindle endings (MSEs) and tendon organs (TOs) on medullary inspiratory activity in decerebrate and allobarbital-anesthetized cats. Impeded muscle contractions, elicited by electrical stimulation of the peripheral cut end of the T6 ventral root, were used to stimulate external and internal intercostal TOs without MSEs. Impeded contractions of either the external or internal intercostal muscles reduced phrenic and medullary inspiratory neuronal activities. Vibration was used to selectively stimulate external or internal intercostal MSEs (90 and 40 micron amplitude, respectively). Selective stimulation of either external or internal intercostal MSEs did not change phrenic or medullary inspiratory neuronal activities. It is concluded that both external and internal intercostal TOs have a generalized inhibitory effect on medullary inspiratory activity and intercostal MSEs have no effect on medullary inspiratory activity.

Inspiratory neuron activity in the ventrolateral medulla of the dog

1987 ◽  
Vol 62 (1) ◽  
pp. 335-343 ◽  
Author(s):  
E. M. Adams ◽  
A. D. Horres ◽  
R. Frayser
Keyword(s):  
Minute Ventilation ◽  
Peak Frequency ◽  
Respiratory Neurons ◽  
Ventrolateral Medulla ◽  
Neuron Activity ◽  
Blue Dye ◽  
Tracheal Occlusion ◽  
Time To Peak ◽  
Burst Pattern ◽  
Inspiratory Neuron

The purpose of this study was to describe the distribution and activity pattern of respiratory neurons located in the ventrolateral medulla (VLM) of the dog. Spike activity of 129 respiratory neurons was recorded in 23 ketamine-anesthetized spontaneously breathing dogs. Pontamine blue dye was used to mark the location of each neuron. Most VLM neurons displaying respiratory related spike patterns were located in a column related closely to ambigual and retroambigual nuclei. Both inspiratory and expiratory neurons were present with inspiratory units being grouped more rostrally. The predominant inspiratory neuron firing pattern was “late” inspiratory, although eight “early” types were located. All expiratory firing patterns were the late expiratory variety. Each neuron burst pattern was characterized by determining burst duration (BD), spikes per burst (S/B), peak frequency (PF), time to peak frequency (TPF), rate of rise to peak frequency (PF/TPF), and mean frequency. CO2-induced minute ventilation increases were associated with decreases in BD and TPF and increases in PF, S/B, and PF/TPF. In 11 experiments the relative influences of vagotomy and tracheal occlusion on late inspiratory units were compared. Tracheal occlusion increased late inspiratory BD and S/B but did not alter PF/TPF. Vagotomy increased BD and S/B beyond those obtained by tracheal occlusion and, in some neurons, decreased the PF/TPF. We conclude that the location of respiratory units in the VLM of the dog is similar to that in other species, the discharge pattern of VLM respiratory units is similar to those in cat VLM, and vagotomy and tracheal occlusion affect discharge patterns differently.

Inhibition of cardiac vagal component of baroreflex by group III and IV afferents

1991 ◽  
Vol 260 (3) ◽  
pp. H730-H734 ◽  
Author(s):  
P. N. McWilliam ◽  
T. Yang
Keyword(s):  
Peroneal Nerve ◽  
Baroreceptor Reflex ◽  
Interval Prolongation ◽  
Group Iii ◽  
Control Value ◽  
Pressure Elevation ◽  
Group I ◽  
Afferent Fibers ◽  
The Difference ◽  
The Right

The action of electrically evoked activity in somatic afferent fibers on the sensitivity of the baroreceptor reflex was examined in decerebrate cats. The sensitivity of the reflex was expressed as the difference between the maximum prolongation of R-R interval in response to carotid sinus pressure elevation and the mean of 10 R-R intervals immediately before pressure elevation. The control value of R-R interval prolongation was 192 +/- 50 ms. Stimulation (10 Hz) of group I and II fibers of the right peroneal nerve (evoked volleys recorded from the sciatic nerve) had no effect on R-R interval prolongation (171 +/- 45 ms). Recruitment of group III fibers (10 Hz) conducting at 23.6 +/- 0.65 m/s reduced the prolongation of R-R interval to 52 +/- 14 ms. Recruitment of group IV fibers (10 Hz) conducting less than 2.5 m/s further reduced the prolongation of R-R interval to 1.0 +/- 8.0 ms. It is concluded that the inhibition of the cardiac vagal component of the baroreceptor reflex produced by electrical stimulation of the peroneal nerve is mediated by afferent fibers of groups III and IV.

Ensemble discharge from Golgi tendon organs of cat peroneus tertius muscle

1990 ◽  
Vol 64 (3) ◽  
pp. 813-821 ◽  
Author(s):  
G. Horcholle-Bossavit ◽  
L. Jami ◽  
J. Petit ◽  
R. Vejsada ◽  
D. Zytnicki
Keyword(s):  
Motor Unit ◽  
Motor Units ◽  
Good Correspondence ◽  
Golgi Tendon Organs ◽  
Afferent Fibers ◽  
Slow Type ◽  
Tendon Organs ◽  
Fast Twitch ◽  
Force Profiles ◽  
Tendon Organ

1. The responses of individual tendon organs of the cat peroneus tertius muscle to motor-unit contractions were recorded in anesthetized cats during experiments in which all the Ib-afferent fibers from the muscle had been prepared for recording in dorsal root filaments. This was possible because the cat peroneus tertius only contains a relatively small complement of approximately 10 tendon organs. 2. Motor units of different physiological types were tested for their effects on the whole population of tendon organs in the muscle. Effects of unfused tetanic contractions were tested under both isometric and anisometric conditions. Each motor unit activated at least one tendon organ, and each tendon organ was activated by at least one motor unit. Individual slow-type units were found to act on a single or two receptors, whereas a fast-type unit could activate up to six tendon organs. 3. In one experiment, the effects of 8 motor units on 10 tendon organs were examined. One fast-twitch, fatigue resistant (FR)-type unit acted on six tendon organs, of which four were also activated by another FR unit. The contraction of each unit, on its own, elicited a range of individual responses, from weak to strong. The discharge frequencies of individual responses displayed no clear relation with the strength of contraction, nor did they accurately represent the shape of force profiles. But when all the discharges were pooled, a fairly good correspondence appeared between variations of contractile force and variations of averaged discharge frequencies.(ABSTRACT TRUNCATED AT 250 WORDS)

Integration of vagal afferent responses to gastric loads and cholecystokinin in rats

1991 ◽  
Vol 261 (1) ◽  
pp. R64-R69 ◽  
Author(s):  
G. J. Schwartz ◽  
P. R. McHugh ◽  
T. H. Moran
Keyword(s):  
Discharge Rate ◽  
Celiac Artery ◽  
Gastric Volume ◽  
Afferent Activity ◽  
Rapid Adaptation ◽  
Discharge Rates ◽  
Group I ◽  
Afferent Fibers ◽  
Vagal Afferent ◽  
Contrast Group

The neurophysiological responses to 2-ml intragastric saline loads and 100-pmol celiac artery infusions of cholecystokinin (CCK) were obtained from 20 vagal afferent fibers in 14 rats. Two groups of fibers were identified. Discharge rates of group I fibers (n = 16) were significantly increased by gastric loading, adapted slowly to maintained gastric volume, and were inhibited by load withdrawal. CCK elicited a significant increase in the discharge rate of these group I fibers. Prior exposure to CCK nearly doubled the response of these fibers to a subsequent gastric load. In contrast, group II fibers (n = 4) increased firing rate only during infusion of a gastric load and showed rapid adaptation and no response to CCK. CCK failed to alter subsequent responses to gastric loads in these fibers. These results 1) demonstrate an integration of signals elicited by exogenous CCK and gastric loads at the level of vagal afferent fibers and 2) imply that aspects of CCK's inhibition of food intake may derive from CCK's ability to mimic and amplify vagal afferent activity provoked by meal-related gastric events.

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