Medullary lateral tegmental field: an important source  of basal sympathetic nerve discharge in the cat

Barman, Susan M.; Gebber, Gerard L.; Orer, Hakan S.

doi:10.1152/ajpregu.2000.278.4.r995

Cited by 33 publications

(64 citation statements)

References 39 publications

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“…In the current study, chemical inactivation of the LTF reduced total power in the 0-to 5-Hz band of SND to 75% of control. Moreover, our past work (10,45) showed that SND was reduced to ϳ50% of control after blockade of non-NMDA receptor-mediated transmission in the LTF of baroreceptor-innervated and -denervated cats. These observations support the view that the LTF plays an important role in setting the level of basal SND, at least in the cat.…”

Section: Ltf and Vagal Lung Inflation Afferentsmentioning

confidence: 97%

“…2, 6, and 8), the data block beginning 10 min after microinjection was used to quantify the effects of chemical inactivation of the LTF on the interrelationships of ITP, SND, and PNA. This time point was chosen because our past work showed that the maximum changes in basal SND had occurred at this time, and SND had reached a new steady-state level (9,10,45).…”

Section: Microinjectionsmentioning

confidence: 99%

“…Several laboratories have shown that this region of the cat brain stem contains neurons with activity correlated to SND (7-9, 12, 18, 30, 56), and chemical activation of the LTF can alter blood pressure (17,26,32,41,54). Importantly, there is a growing body of evidence supporting the view that, at least in the cat, the LTF plays a crucial role not only in setting the basal level of SND (9,10,45) but also in mediating responses to activation of baroreceptor and chemoreceptor afferents (45,46). Specifically, blockade of non-N-methyl-D-aspartate (non-NMDA) receptors in the LTF reduced the level of basal SND and the sympathoexcitatory effect of arterial chemoreceptor activation (10,45,46), whereas blockade of NMDA receptors attenuated baroreflexmediated sympathoinhibition (45).…”

mentioning

confidence: 99%

“…Importantly, there is a growing body of evidence supporting the view that, at least in the cat, the LTF plays a crucial role not only in setting the basal level of SND (9,10,45) but also in mediating responses to activation of baroreceptor and chemoreceptor afferents (45,46). Specifically, blockade of non-N-methyl-D-aspartate (non-NMDA) receptors in the LTF reduced the level of basal SND and the sympathoexcitatory effect of arterial chemoreceptor activation (10,45,46), whereas blockade of NMDA receptors attenuated baroreflexmediated sympathoinhibition (45). These observations prompted us in the current study to test the hypothesis that the LTF is involved in mediating the effects of vagal lung inflation afferents on SND and PNA.…”

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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: Ltf and Vagal Lung Inflation Afferentsmentioning

confidence: 97%

Section: Microinjectionsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

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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“…Procedures used for exposing the brain stem and for microinjection of drugs into the LTF are the same as those described in earlier reports from this laboratory (4,26,27,29). In fact, the cats in which we studied the effects of muscimol microinjection into the LTF on the Bezold-Jarisch reflex were also included in the study of the effects of chemical inactivation of the LTF on the influence of vagal lung inflation afferents on SND and PNA (29).…”

Section: Microinjectionsmentioning

confidence: 99%

Medullary lateral tegmental field mediates the cardiovascular but not respiratory component of the Bezold-Jarisch reflex in the cat

Barman¹,

Phillips²,

Gebber³

2005

American Journal of Physiology-Regulatory, Integrative and Comp

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Barman, Susan M., Shaun W. Phillips, and Gerard L. Gebber. Medullary lateral tegmental field mediates the cardiovascular but not respiratory component of the Bezold-Jarisch reflex in the cat. Am J Physiol Regul Integr Comp Physiol 289: R1693-R1702, 2005. First published August 11, 2005; doi:10.1152/ajpregu.00406.2005.-We determined the effects of bilateral microinjection of muscimol and excitatory amino acid receptor antagonists into the medullary lateral tegmental field (LTF) on changes in sympathetic nerve discharge (SND), mean arterial pressure (MAP), and phrenic nerve activity (PNA; artificially ventilated cats) or intratracheal pressure (spontaneously breathing cats) elicited by right atrial administration of phenylbiguanide (PBG; i.e., the Bezold-Jarisch reflex) in dial-urethane anesthetized cats. The PBG-induced depressor response (Ϫ66 Ϯ 8 mmHg; mean Ϯ SE) was converted to a pressor response after muscimol microinjection in two of three spontaneously breathing cats and was markedly reduced in the other cat; however, the duration of apnea (20 Ϯ 3 vs. 17 Ϯ 7 s) was essentially unchanged. In seven paralyzed, artificially ventilated cats, muscimol microinjection significantly (P Ͻ 0.05) attenuated the PBG-induced fall in MAP (Ϫ39 Ϯ 7 vs. Ϫ4 Ϯ 4 mmHg) and the magnitude (Ϫ98 Ϯ 1 vs. Ϫ35 Ϯ 13%) and duration (15 Ϯ 2 vs. 3 Ϯ 2 s) of the sympathoinhibitory response. In contrast, the PBG-induced inhibition of PNA was unaffected (3 cats). Similar results were obtained by microinjection of an N-methyl-D-aspartate (NMDA) receptor antagonist, D(-)-2-amino-5-phosphonopentanoic acid, into the LTF. In contrast, neither the cardiovascular nor respiratory responses to PBG were altered by blockade of non-NMDA receptors with 1,2,3,4-tetrahydro-6-nitro-2,3-dioxobenzo[f]quinoxaline-7-sulfonamide. We conclude that the LTF subserves a critical role in mediating the sympathetic and cardiovascular components of the Bezold-Jarisch reflex. Moreover, these data show separation of the pathways mediating the respiratory and cardiovascular responses of this reflex at a level central to bulbospinal outflows to phrenic motoneurons and preganglionic sympathetic neurons. cardiopulmonary chemosensitive afferent; medullary lateral tegmental field; phrenic nerve activity; sympathetic nerve discharge; vagal afferent SINCE THE PIONEERING WORK of von Bezold and Hirt (42) and Jarisch and Henze (18), many investigators have shown that activation of chemosensitive vagal C fibers in the cardiopulmonary region (e.g., juxtacapillary region of the alveoli, ventricles, atria, great veins, and pulmonary artery) leads to a profound bradycardia, hypotension, and a brief period of apnea followed by rapid shallow breathing [see reviews by Hainsworth (17) and Verberne et al. (39)]. The Bezold-Jarisch reflex can be elicited by a variety of substances including capsaicin, serotonin, phenylbiguanide (PBG), and veratridine in cats, rabbits, and rodents (9,11,14,20,28,33,36,37,41). Although originally viewed as a pharmacological curiosity, there is a growing body of...

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The Presympathetic Cells of the Rostral Ventrolateral Medulla (RVLM): Anatomy, Physiology and Role in the Control of Circulation

Guyenet

2004

Neural Mechanisms of Cardiovascular Regulation

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Medullary lateral tegmental field: an important source of basal sympathetic nerve discharge in the cat

Cited by 33 publications

References 39 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

Medullary lateral tegmental field mediates the cardiovascular but not respiratory component of the Bezold-Jarisch reflex in the cat

The Presympathetic Cells of the Rostral Ventrolateral Medulla (RVLM): Anatomy, Physiology and Role in the Control of Circulation

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