Inputs to intercostal motoneurons from ventrolateral medullary respiratory neurons in the cat

1987 ◽  
Vol 57 (6) ◽  
pp. 1837-1853 ◽  
Author(s):  
E. G. Merrill ◽  
J. Lipski
Keyword(s):  
Membrane Potential ◽  
Respiratory Neurons ◽  
Respiratory Drive ◽  
Thoracic Spinal Cord ◽  
Medullary Respiratory Neurons ◽  
Thoracic Spinal ◽  
Synaptic Noise ◽  
Series Of Experiments ◽  
Intercostal Nerves ◽  
Descending Projections

The investigation examined the synaptic input from medullary respiratory neurons in the nucleus retroambigualis (NRA) to external (EIM) and internal (IIM) intercostal motoneurons. Antidromic mapping revealed that 112/117 (96%) tested NRA units had axons descending into thoracic spinal cord with extensive arborizations at many thoracic segments, mainly contralaterally. The conduction velocities ranged from 10 to 105 m X s-1. The descending projections did not appear to be somatotopically arranged. Cross-correlation of the spike trains of NRA inspiratory units with the discharge of external intercostal nerves (performed usually with 4 contralateral nerves) showed significant narrow peaks only in 5 out of 40 averages. Of the 25 trigger units tested for the thoracic projection in this series of experiments, 24 were antidromically activated. Intracellular recordings were made from 52 IIMs [mean membrane potential 65.3 mV, central respiratory drive potentials (CRDPs) greater than 1 mV present in 23/52] and 53 EIM (mean membrane potential 54.3 mV, CRDPs in 31/53). During the depolarizing phase of the CRDPs, synaptic noise with frequent and apparently unitary EPSPs with amplitudes in excess of 1 mV was observed. Spike-triggered averages of synaptic noise were computed for 153 pairings between 137 NRA neurons and 105 contralateral intercostal motoneurons. Only four PSPs were revealed: two monosynaptic EPSPs between expiratory NRA units and IIMs and two probably disynaptic EPSPs between inspiratory NRA units and EIMs. When advancing the microelectrode down to the motoneuron pools, frequent recordings were made from interneurons with spontaneous respiratory discharge (inspiratory or expiratory) located dorsal and medial to the motor nuclei. The interneurons could be excited following stimulation of segmental afferents. It is concluded that monosynaptic connections between respiratory NRA neurons and intercostal motoneurons are rare (connectivity no more than approximately 4%). Segmental interneurons, interposed between the majority of descending respiratory axons and intercostal motoneurons, are likely to produce large unitary EPSPs and, thus, short-term synchronization in the discharge of intercostal motoneurons as observed by others.

Accommodative reactions of medullary respiratory neurons of the cat

1975 ◽  
Vol 38 (5) ◽  
pp. 1172-1180 ◽  
Author(s):  
D. W. Richter ◽  
F. Heyde
Keyword(s):  
Membrane Potential ◽  
Synaptic Input ◽  
Early Period ◽  
Rhythmic Activity ◽  
Respiratory Neurons ◽  
Current Frequency ◽  
Burst Discharge ◽  
Current Pulses ◽  
Medullary Respiratory Neurons ◽  
Frequency Relationship

In most of the bulbospinal respiratory neurons, threshold depolarization increased during the early period of their spontaneous burst discharge but decreased again at the end of a burst. In some vagal respiratory neurons, however, threshold depolarization increased steadily until the very end of their discharge period. These changes generally were accompanied by changes in the rate of depol1rization of the spikes, the amplitude of their overshoot, and their discharge frequency. For a given synaptic input, as indicated by the constancy of the interspike membrane potential trajectories, threshold depolarization of bulbospinal neurons remained constant or even decreased. Only in some vagal neurons was an increase in threshold deplarization observed under these conditions. With the exception of some vagal neurons, most of the respiratory neurons did not show a pronounced accommodative behavior when stimulated with linear rising currents. When stimulating with current pulses, all neurons discharged repetitively with only slight adaptation, which was already complete by the first few spike intervals. The current-frequency relationship was linear and revealed a primary and secondary range. The results support neither accommodation nor adaptation as important mechanisms in the genesis of the rhythmic activity of respiratory neurons.

Changes in antidromic latencies of medullary respiratory neurons in hypercapnia and hypoxia

1985 ◽  
Vol 59 (4) ◽  
pp. 1208-1213 ◽  
Author(s):  
A. L. Bianchi ◽  
W. M. St John
Keyword(s):  
Membrane Potential ◽  
Neuronal Activity ◽  
Membrane Potentials ◽  
Respiratory Neurons ◽  
Strongly Correlated ◽  
Antidromic Activation ◽  
Axonal Projections ◽  
Medullary Respiratory Neurons ◽  
Spontaneous Neuronal Activity ◽  
The Difference

We evaluated mechanisms underlying changes in discharge frequencies of medullary respiratory neurons. This evaluation was made by determining variations in antidromic latencies; these variations reflect changes in membrane potentials. In decerebrate, vagotomized, paralyzed, and ventilated cats, activities of the phrenic nerve and single respiratory neurons were monitored in hyperoxic normocapnia, hyperoxic hypercapnia, and/or normocapnic hypoxia. Axonal projections were defined as bulbospinal or laryngeal by antidromic activation. At normocapnic hyperoxia, antidromic latencies fell to minima during periods of spontaneous neuronal activity, with maxima occurring between neuronal bursts. In hypercapnia or hypoxia, these minima were not altered, whereas maximum latencies typically rose for neurons whose discharge frequencies increased. However, the increased frequencies most strongly correlated with increases in the difference between maximum and minimum latencies. No such correlation was evident for neurons whose discharge frequencies declined. We conclude that the overall change of membrane potential primarily defines neuronal discharge frequencies. Changes in membrane potentials induced by peripheral and central chemoreceptor afferents and by direct actions of hypercapnia and hypoxia are discussed.

scholarly journals Functional plasticity in the respiratory drive to thoracic motoneurons in the segment above a chronic lateral spinal cord lesion

2016 ◽  
Vol 115 (1) ◽  
pp. 554-567 ◽  
Author(s):  
T. W. Ford ◽  
N. P. Anissimova ◽  
C. F. Meehan ◽  
P. A. Kirkwood
Keyword(s):  
Spinal Cord ◽  
Spinal Cord Lesion ◽  
Similar Distribution ◽  
Respiratory Drive ◽  
Functional Plasticity ◽  
Thoracic Spinal Cord ◽  
Thoracic Spinal ◽  
Spike Triggered Averaging ◽  
The Right ◽  
Cord Lesion

A previous neurophysiological investigation demonstrated an increase in functional projections of expiratory bulbospinal neurons (EBSNs) in the segment above a chronic lateral thoracic spinal cord lesion that severed their axons. We have now investigated how this plasticity might be manifested in thoracic motoneurons by measuring their respiratory drive and the connections to them from individual EBSNs. In anesthetized cats, simultaneous recordings were made intracellularly from motoneurons in the segment above a left-side chronic (16 wk) lesion of the spinal cord in the rostral part of T8, T9, or T10 and extracellularly from EBSNs in the right caudal medulla, antidromically excited from just above the lesion but not from below. Spike-triggered averaging was used to measure the connections between pairs of EBSNs and motoneurons. Connections were found to have a very similar distribution to normal and were, if anything (nonsignificantly), weaker than normal, being present for 42/158 pairs, vs. 55/154 pairs in controls. The expiratory drive in expiratory motoneurons appeared stronger than in controls but again not significantly so. Thus we conclude that new connections made by the EBSNs following these lesions were made to neurons other than α-motoneurons. However, a previously unidentified form of functional plasticity was seen in that there was a significant increase in the excitation of motoneurons during postinspiration, being manifest either in increased incidence of expiratory decrementing respiratory drive potentials or in an increased amplitude of the postinspiratory depolarizing phase in inspiratory motoneurons. We suggest that this component arose from spinal cord interneurons.

scholarly journals Electrophysiological and Morphological Characterization of Propriospinal Interneurons in the Thoracic Spinal Cord

2011 ◽  
Vol 105 (2) ◽  
pp. 806-826 ◽  
Author(s):  
S. A. Saywell ◽  
T. W. Ford ◽  
C. F. Meehan ◽  
A. J. Todd ◽  
P. A. Kirkwood
Keyword(s):  
Spinal Cord ◽  
General Pattern ◽  
Morphological Characterization ◽  
Ventral Horn ◽  
Trunk Muscles ◽  
Respiratory Drive ◽  
Thoracic Spinal Cord ◽  
Antidromic Activation ◽  
Thoracic Spinal ◽  
Cord Injury

Propriospinal interneurons in the thoracic spinal cord have vital roles not only in controlling respiratory and trunk muscles, but also in providing possible substrates for recovery from spinal cord injury. Intracellular recordings were made from such interneurons in anesthetized cats under neuromuscular blockade and with the respiratory drive stimulated by inhaled CO2. The majority of the interneurons were shown by antidromic activation to have axons descending for at least two to four segments, mostly contralateral to the soma. In all, 81% of the neurons showed postsynaptic potentials (PSPs) to stimulation of intercostal or dorsal ramus nerves of the same segment for low-threshold (≤5T) afferents. A monosynaptic component was present for the majority of the peripherally evoked excitatory PSPs. A central respiratory drive potential was present in most of the recordings, usually of small amplitude. Neurons depolarized in either inspiration or expiration, sometimes variably. The morphology of 17 of the interneurons and/or of their axons was studied following intracellular injection of Neurobiotin; 14 axons were descending, 6 with an additional ascending branch, and 3 were ascending (perhaps actually representing ascending tract cells); 15 axons were crossed, 2 ipsilateral, none bilateral. Collaterals were identified for 13 axons, showing exclusively unilateral projections. The collaterals were widely spaced and their terminations showed a variety of restricted locations in the ventral horn or intermediate area. Despite heterogeneity in detail, both physiological and morphological, which suggests heterogeneity of function, the projections mostly fitted a consistent general pattern: crossed axons, with locally weak, but widely distributed terminations.

Spontaneous Herniation of the Thoracic Spinal Cord: A Case Report

2001 ◽  
Vol 45 (4) ◽  
pp. 353 ◽  
Author(s):  
Sung Chan Jin ◽  
Seoung Ro Lee ◽  
Dong Woo Park ◽  
Kyung Bin Joo
Keyword(s):  
Spinal Cord ◽  
Case Report ◽  
Thoracic Spinal Cord ◽  
Thoracic Spinal ◽  
Spontaneous Herniation

Lipomeningocele associated with diplomyelia in a dog

2018 ◽  
Vol 46 (05) ◽  
pp. 323-329 ◽  
Author(s):  
Nele Ondreka ◽  
Sara Malberg ◽  
Emma Laws ◽  
Martin Schmidt ◽  
Sabine Schulze
Keyword(s):  
Spinal Cord ◽  
Neurological Status ◽  
Split Cord Malformation ◽  
Lumbar Spinal Cord ◽  
Histopathological Diagnosis ◽  
Type I ◽  
Thoracic Spinal Cord ◽  
Thoracic Spinal ◽  
Subcutaneous Mass ◽  
Lumbar Spinal

SummaryA 2-year-old male neutered mixed breed dog with a body weight of 30 kg was presented for evaluation of a soft subcutaneous mass on the dorsal midline at the level of the caudal thoracic spine. A further clinical sign was intermittent pain on palpation of the area of the subcutaneous mass. The owner also described a prolonged phase of urination with repeated interruption and re-initiation of voiding. The findings of the neurological examination were consistent with a lesion localization between the 3rd thoracic and 3rd lumbar spinal cord segments. Magnetic resonance imaging revealed a spina bifida with a lipomeningocele and diplomyelia (split cord malformation type I) at the level of thoracic vertebra 11 and 12 and secondary syringomyelia above the aforementioned defects in the caudal thoracic spinal cord. Surgical resection of the lipomeningocele via a hemilaminectomy was performed. After initial deterioration of the neurological status postsurgery with paraplegia and absent deep pain sensation the dog improved within 2 weeks to non-ambulatory paraparesis with voluntary urination. Six weeks postoperatively the dog was ambulatory, according to the owner. Two years after surgery the owner recorded that the dog showed a normal gait, a normal urination and no pain. Histopathological diagnosis of the biopsied material revealed a lipomeningocele which confirmed the radiological diagnosis.

Primary Melanocytoma of the Lower Thoracic Spinal Cord: Case report and review of the literature

2019 ◽  
Vol 8 (1) ◽  
pp. 5
Author(s):  
Dimitrios Panagopoulos
Keyword(s):  
Total Resection ◽  
Thoracic Spinal Cord ◽  
Meningeal Melanocytoma ◽  
Melanocytic Tumors ◽  
Thoracic Spinal ◽  
Thoracolumbar Region ◽  
Rare Benign Tumor ◽  
Mri Scans ◽  
History Of ◽  
The Central Nervous System

Background: Meningeal melanocytoma is a rare benign tumor, most frequently located in the posterior fossa and spinal canal. Our objective is to illustrate a case of this tumor that originated in the thoracolumbar area of the spine and had an uneventful clinical course after total resection. Case description: We present the case of a 59 years old woman who presented with a medical history of ongoing neurological deterioration due to spastic paresis of the lower extremities. MRI of the thoracolumbar region identified a melanocytic melanoma as the underlying cause. Conclusions: Melanocytic tumors of the central nervous system have a typical appearance on MRI scans, varying with the content and distribution of melanin. However, the differential diagnosis between malignant melanoma and melanocytoma still depends on pathological criteria. Spinal meningeal melanocytoma has a benign course, and it is amenable for gross total resection. The outcome is favorable following complete resection.

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