Medullary lateral tegmental field: an important synaptic  relay in the baroreceptor reflex pathway of the cat

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

doi:10.1152/ajpregu.1999.277.5.r1462

Cited by 28 publications

(105 citation statements)

References 32 publications

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“…If such is the case, one could suggest that our data merely confirm our past work showing a role of the LTF in mediating the baroreflex in the cat (45). However, this explanation is not tenable for several reasons.…”

Section: Ltf and Vagal Lung Inflation Afferentssupporting

confidence: 61%

“…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: 96%

“…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.…”

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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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 Afferentssupporting

confidence: 61%

Section: Ltf and Vagal Lung Inflation Afferentsmentioning

confidence: 96%

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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Processing of vestibular inputs by the medullary lateral tegmental field of conscious cats: implications for generation of motion sickness

et al. 2012

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The dorsolateral reticular formation of the caudal medulla, the lateral tegmental field (LTF), participates in generating vomiting. LTF neurons exhibited complex responses to vestibular stimulation in decerebrate cats, indicating that they received converging inputs from a variety of labyrinthine receptors. Such a convergence pattern of vestibular inputs is appropriate for a brain region that participates in generating motion sickness. Since responses of brainstem neurons to vestibular stimulation can differ between decerebrate and conscious animals, the current study examined the effects of whole-body rotations in vertical planes on the activity of LTF neurons in conscious felines. Wobble stimuli, fixed-amplitude tilts, the direction of which moves around the animal at a constant speed, were used to determine the response vector orientation, and also to ascertain whether neurons had spatial–temporal convergence (STC) behavior (which is due to the convergence of vestibular inputs with different spatial and temporal properties). The proportion of LTF neurons with STC behavior in conscious animals (25 %) was similar to that in decerebrate cats. Far fewer neurons in other regions of the feline brainstem had STC behavior, confirming findings that many LTF neurons receive converging inputs from a variety of labyrinthine receptors. However, responses to vertical plane vestibular stimulation were considerably different in decerebrate and conscious felines for LTF neurons lacking STC behavior. In decerebrate cats, most LTF neurons had graviceptive responses to rotations, similar to those of otolith organ afferents. However, in conscious animals, the response properties were similar to those of semicircular canal afferents. These differences show that higher centers of the brain that are removed during decerebration regulate the labyrinthine inputs relayed to the LTF, either by gating connections in the brainstem or by conveying vestibular inputs directly to the region.

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Role of medullary excitatory amino acid receptors in mediating the 10-Hz rhythm in sympathetic nerve discharge of cats

2005

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Medullary lateral tegmental field: an important synaptic relay in the baroreceptor reflex pathway of the cat

Cited by 28 publications

References 32 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

Processing of vestibular inputs by the medullary lateral tegmental field of conscious cats: implications for generation of motion sickness

Role of medullary excitatory amino acid receptors in mediating the 10-Hz rhythm in sympathetic nerve discharge of cats

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