Interactions among inspiratory neurons in dorsal and ventral respiratory groups in cat medulla

Feldman, J; Speck, D. F.

doi:10.1152/jn.1983.49.2.472

Cited by 78 publications

(28 citation statements)

References 14 publications

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“…However, interruption of vagal lung inflation afferent input to DRG neurons cannot fully explain the pro-longation of the inspiratory burst because chemical inactivation of this region in vagotomized cats also increased I-duration. Moreover, microinjection of muscimol into the DRG reduced the slope of the ramplike increase in PNA, whereas simple interruption of the Hering-Breuer reflex by withholding lung inflation does not (20,22,29). The differences between chemical inactivation of the DRG and interruption of vagal lung inflation afferent input to DRG neurons likely reflects the fact that there are multiple mechanisms within this region that act to terminate inspiration (19,28).…”

Section: Did Muscimol Act Within the Ltf Or Spread To Other Medullarymentioning

confidence: 99%

“…Specifically, the pipette was positioned 3.8 mm lateral to the midline at a depth of 3.8 mm below the dorsal surface in tracks located ϳ2 and 3 mm rostral to the obex (same stereotaxic planes as LTF injection sites). Others (2,23,29,52) have shown that this portion of the VRG contains neurons with inspiratory-related activity, including some that project to the spinal cord.…”

Section: Microinjectionsmentioning

confidence: 99%

“…We determined if the increases in central respiratory rate produced by microinjection of muscimol into the LTF could be explained by spread of the injectate to adjacent medullary regions with known respiratory functions, i.e., the VRG and DRG (16,19,28,29,47,48). We also determined the effects of chemical inactivation of these regions on the relationship of ITP to SND and PNA in these cats.…”

Section: Effects Of Microinjection Of Muscimol Into the Vicinity Of Tmentioning

confidence: 99%

“…It may seem surprising that chemical inactivation of this region caused only a modest reduction in the inspiratory burst amplitude since this portion of the VRG contains inspiratory premotor neurons (23,29). However, it should be noted that we injected muscimol into only a small portion of the VRG which, in its entirety, extends from 10 mm from the spinomedullary border to the retrofacial nucleus (29). Also, our data corroborate the findings of Anderson and Speck (2) who showed that blockade of excitatory amino acid receptors in the same region of the VRG did not markedly affect PNA.…”

Section: Did Muscimol Act Within the Ltf Or Spread To Other Medullarymentioning

confidence: 99%

“…These effects were likely due, at least in part, to block of the Hering-Breuer reflex because vagal lung inflation afferents terminate in the ventrolateral NTS (27,29,58). The DRG contains several types of neurons, including pump cells and late-inspiratory neurons, that are thought to be involved in mediating the Hering-Breuer reflex (20,22).…”

Section: Did Muscimol Act Within the Ltf Or Spread To Other Medullarymentioning

confidence: 99%

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Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

Phillips¹,

Gebber²,

Barman³

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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Phillips, Shaun W., Gerard L. Gebber, and Susan M. Barman. Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge. Am J Physiol Regul Integr Comp Physiol 288: R1396 -R1410, 2005. First published December 16, 2004; doi:10.1152/ajpregu.00632.2004.-We used spectral analysis and event-triggered averaging to determine the effects of chemical inactivation of the medullary lateral tegmental field (LTF) on 1) the relationship of intratracheal pressure (ITP, an index of vagal lung inflation afferent activity) to sympathetic nerve discharge (SND) and phrenic nerve activity (PNA) and 2) central respiratory rate in paralyzed, artificially ventilated dial-urethane-anesthetized cats. ITP-SND coherence value at the frequency of artificial ventilation was significantly (P Ͻ 0.05; n ϭ 18) reduced from 0.73 Ϯ 0.04 (mean Ϯ SE) to 0.24 Ϯ 0.04 after bilateral microinjection of muscimol into the LTF. Central respiratory rate was unexpectedly increased in 12 of these experiments (0.28 Ϯ 0.03 vs. 0.95 Ϯ 0.25 Hz). The ITP-PNA coherence value was variably affected by chemical inactivation of the LTF. It was unchanged when central respiratory rate was also not altered, decreased when respiratory rate was increased above the rate of artificial ventilation, and increased when respiratory rate was raised from a value below the rate of artificial ventilation to the same frequency as the ventilator. Chemical inactivation of the LTF increased central respiratory rate in four of six vagotomized cats but did not significantly affect the PNA-SND coherence value. These data demonstrate that the LTF 1) plays a critical role in mediating the effects of vagal lung inflation afferents on SND but not PNA, 2) helps maintain central respiratory rate in the physiological range, but 3) is not involved in the coupling of central respiratory and sympathetic circuits. cardiorespiratory synchronization; dorsal respiratory group; HeringBreuer reflex; phrenic nerve activity; respiratory-related rhythm; ventral respiratory group IT HAS LONG BEEN RECOGNIZED that neural mechanisms controlling the respiratory and cardiovascular systems are tightly linked (25,34,38,49,55). This interaction facilitates the complementary functions of the two systems: respiration maintains appropriate levels of arterial blood gases, while the cardiovascular system transports these gases to and from tissues. One indication of this cardiorespiratory coordination was noted by Adrian et al. (1) in 1932 when they made the first recordings of sympathetic nerve discharge (SND). They found that the amplitude of the cardiac-related bursts of SND waxed and waned on the time scale of the respiratory cycle. There are at least two sources of respiratory modulation of SND: input from vagal lung inflation afferents and an influence of the respiratory rhythm generator on central sympathetic neurons (4 -6, 21, 25, 33-35, 59). Although some investigators (38, 49) have proposed that there is a common network controlling bo...

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Section: Did Muscimol Act Within the Ltf Or Spread To Other Medullarymentioning

confidence: 99%

Section: Microinjectionsmentioning

confidence: 99%

Section: Effects Of Microinjection Of Muscimol Into the Vicinity Of Tmentioning

confidence: 99%

Section: Did Muscimol Act Within the Ltf Or Spread To Other Medullarymentioning

confidence: 99%

Section: Did Muscimol Act Within the Ltf Or Spread To Other Medullarymentioning

confidence: 99%

See 3 more Smart Citations

Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

Phillips¹,

Gebber²,

Barman³

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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Distribution of N-methyl-D-aspartate and non-N-methyl-D-aspartate glutamate receptor subunits on respiratory motor and premotor neurons in the rat

Robinson

Ellenberger

1997

J. Comp. Neurol.

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Glutamate is required for the transmission of inspiratory drive in respiratory premotor and motor neurons. The glutamate receptors (GluRs) responsible for this essential function have yet to be anatomically characterized. We mapped the GluR subtypes expressed by respiratory premotor and motor neurons by using combined immunohistochemistry and retrograde labeling in adult rats. Phrenic motoneurons and bulbospinal ventral respiratory group (VRG) neurons were retrogradely labeled and immunolabeled with subunit-specific antibodies against the N-methyl-D-aspartate (NMDA) receptor subtype (NMDAR1) and the non-NMDA receptor subtypes, alpha-amino-3-hydroxy-5-methylisoxazole-4-proprionic acid (AMPA; GluR1, GluR2/3, GluR4) and kainate (GluR5-7). Phrenic motoneurons and bulbospinal VRG neurons showed positive immunolabeling for all five GluR subunits. These results support the hypothesis that NMDA and non-NMDA receptor subtypes underlie the excitation of bulbospinal VRG neurons and phrenic motoneurons. Furthermore, immunolabeling for each receptor subtype demonstrated a unique distribution along the neuronal membrane. Immunoreactivity for AMPA receptor subunits was distributed throughout somata and proximal dendrites, NMDAR1 subunit immunolabeling was localized to somata, and GluR5-7 subunit immunolabeling was confined largely to dendrites. The differential distribution of AMPA, kainate, and NMDA receptors on the somal and dendritic surface of respiratory neurons suggests that the location of glutamatergic synapses along the neuronal surface is an important determinant of glutamate-mediated postsynaptic currents. Consequently, different patterns of glutamatergic excitation of respiratory neurons could be achieved by selective activation of different profiles of GluR subtypes on different portions of the neuronal membrane.

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Morphology of inspiratory neurons located in the ventrolateral nucleus of the tractus solitarius of the cat

Berger

Averill

Cameron

1984

J of Comparative Neurology

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The morphology of 11 dorsal respiratory group (DRG) inspiratory neurons located in the ventrolateral nucleus of the solitary tract (vl-NTS) was studied using the technique of intracellular labeling with the enzyme horseradish peroxidase (HRP). Six of these cells were cut in the transverse plane and had a mean somal diameter of 30.4 micron, while five others sectioned in the horizontal plane had a mean of 38.2 micron. These neurons produced an average of 6.2 primary dendrites (range: 4-10), many of which projected rostrally or caudally up to 1.0 mm from the cell bodies. These dendrites were oriented along the longitudinal axis; they ran parallel and ventral to the tractus solitarius. In general, all dendrites possessed numerous spines and appendages. Many axons could be traced for considerable distances within the medulla (in one instance, up to 8 mm). These axons were last discerned in the contralateral ventral medulla rostral to the level of their cell bodies. The axons of three neurons bifurcated in the ipsilateral medulla; one branch remained ipsilateral and projected caudally, while the other crossed the midline. A small number of counterstained cells of size similar to or larger than the HRP-stained neurons formed a column that constituted the vl-NTS. Based upon our observations of stained and counterstained cells, we conclude that the inspiratory neurons of the vl-NTS are few in number and represent a morphologically homogeneous population. The primary orientation of the dendritic arbors of vl-NTS inspiratory neurons appears to optimize the surface area available to receive synaptic contacts from sensory afferents emerging from the tractus solitarius.

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Interactions among inspiratory neurons in dorsal and ventral respiratory groups in cat medulla

Cited by 78 publications

References 14 publications

Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

Medullary lateral tegmental field: control of respiratory rate and vagal lung inflation afferent influences on sympathetic nerve discharge

Distribution of N-methyl-D-aspartate and non-N-methyl-D-aspartate glutamate receptor subunits on respiratory motor and premotor neurons in the rat

Morphology of inspiratory neurons located in the ventrolateral nucleus of the tractus solitarius of the cat

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