Processing of vestibular and other inputs by the caudal ventrolateral medullary reticular formation

Steinbacher, B. C.; Yates, Bill J.

doi:10.1152/ajpregu.1996.271.4.r1070

Cited by 21 publications

(25 citation statements)

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“…Eight neurons responded to both cardiovascular and gastrointestinal stimulation and were classified as convergent neurons. Although transient changes in blood pressure often occurred after delivery of copper sulfate (52,53), the sustained changes in firing rate elicited by infusion of the compound were not synchronized with these blood pressure perturbations. The 31 cells with cardiac-related activity or responses to carotid stretch that were not deemed to be convergent units were classified as cardiovascular neurons.…”

Section: Resultsmentioning

confidence: 95%

Responses of neurons in the caudal medullary lateral tegmental field to visceral inputs and vestibular stimulation in vertical planes

Moy

Miller

Catanzaro

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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The dorsolateral reticular formation of the caudal medulla, or the lateral tegmental field (LTF), has been classified as the brain's "vomiting center", as well as an important region in regulating sympathetic outflow. We examined the responses of LTF neurons in cats to rotations of the body that activate vestibular receptors, as well as to stimulation of baroreceptors (through mechanical stretch of the carotid sinus) and gastrointestinal receptors (through the intragastric administration of the emetic compound copper sulfate). Approximately half of the LTF neurons exhibited graviceptive responses to vestibular stimulation, similar to primary afferents innervating otolith organs. The other half of the neurons had complex responses, including spatiotemporal convergence behavior, suggesting that they received convergent inputs from a variety of vestibular receptors. Neurons that received gastrointestinal and baroreceptor inputs had similar complex responses to vestibular stimulation; such responses are expected for neurons that contribute to the generation of motion sickness. LTF units with convergent baroreceptor and vestibular inputs may participate in producing the cardiovascular system components of motion sickness, such as the changes in skin blood flow that result in pallor. The administration of copper sulfate often modulated the gain of responses of LTF neurons to vestibular stimulation, particularly for units whose spontaneous firing rate was altered by infusion of drug (median of 459%). The present results raise the prospect that emetic signals from the gastrointestinal tract modify the processing of vestibular inputs by LTF neurons, thereby affecting the probability that vomiting will occur as a consequence of motion sickness.

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Section: Resultsmentioning

confidence: 95%

Responses of neurons in the caudal medullary lateral tegmental field to visceral inputs and vestibular stimulation in vertical planes

Moy

Miller

Catanzaro

et al. 2012

American Journal of Physiology-Regulatory, Integrative and Comp

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“…The vestibular nuclei provide direct inputs to the RVLM (28,35), as well as indirect inputs relayed through brain stem regions that mediate the baroreceptor reflex and participate in generating rhythmic SNA, including nucleus tractus solitarius (1,37,41), the lateral tegmental field (40), and the caudal ventrolateral medulla (38). One explanation for the reduced RVLM neuronal activity after the elimination of labyrinthine inputs is a loss of excitatory monosynaptic and polysynaptic excitatory drive to RVLM neurons from the vestibular nuclei.…”

Section: Discussionmentioning

confidence: 99%

Rhythmic activity of neurons in the rostral ventrolateral medulla of conscious cats: effect of removal of vestibular inputs

Barman

Sugiyama²,

Suzuki³

et al. 2011

American Journal of Physiology-Regulatory, Integrative and Comp

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-Although it is well established that bulbospinal neurons located in the rostral ventrolateral medulla (RVLM) play a pivotal role in regulating sympathetic nerve activity and blood pressure, virtually all neurophysiological studies of this region have been conducted in anesthetized or decerebrate animals. In the present study, we used time-and frequency-domain analyses to characterize the naturally occurring discharges of RVLM neurons in conscious cats. Specifically, we compared their activity to fluctuations in carotid artery blood flow to identify neurons with cardiac-related (CR) activity; we then considered whether neurons with CR activity also had a higher-frequency rhythmic firing pattern. In addition, we ascertained whether the surgical removal of vestibular inputs altered the rhythmic discharge properties of RVLM neurons. Less than 10% of RVLM neurons expressed CR activity, although the likelihood of observing a neuron with CR activity in the RVLM varied between recording sessions, even when tracking occurred in a very limited area and was higher after vestibular inputs were surgically removed. Either a 10-Hz or a 20-to 30-Hz rhythmic discharge pattern coexisted with the CR discharges in some of the RVLM neurons. Additionally, the firing rate of RVLM neurons, including those with CR activity, decreased after vestibular lesions. These findings raise the prospect that RVLM neurons may or may not express rhythmic firing patterns at a particular time due to a variety of influences, including descending projections from higher brain centers and sensory inputs, such as those from the vestibular system. vestibular system; sympathetic nervous system; baroreceptors; 10-Hz rhythm; cardiac-related activity THERE IS A CONSENSUS THAT bulbospinal neurons located in the rostral ventrolateral medulla (RVLM) play a pivotal role in regulating the activity of sympathetic preganglionic neurons in the spinal cord that control peripheral vascular resistance and blood pressure (13,15,16). Neurophysiological studies conducted in decerebrate or anesthetized animals have characterized the firing patterns and responses to a variety of stimuli of RVLM neurons (e.g., 3, 5-7, 18, 23). A hallmark of sympathetic nerve activity (SNA) and of the activity in brain stem neurons that regulate cardiovascular function is the appearance of a cardiac-related (CR) rhythm, reflecting the influence of the baroreceptor reflex (14,20,23,25,27). In addition to the CR rhythm, several groups have noted the appearance of a 10-Hz rhythm in SNA of cats (4, 9, 10, 14, 24).We recently provided the first examples of recordings of RVLM neuronal activity in conscious animals (18). In that study, we compared in decerebrate and awake cats the responses of RVLM neurons to whole-body rotations that activate vestibular receptors. We demonstrated that RVLM neuronal responses to vestibular inputs are ordinarily suppressed in conscious animals and hypothesized that autonomic responses to a variety of inputs, including those from the inner ear, are gated by higher brai...

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“…Although the level at which this interaction occurs is unclear, it is generally accepted that the VSR and baroreflexes share common neural pathways (2,45,(51)(52)(53)55). An orthostatic challenge or stimulation of vestibular nuclei is known to cause increases in muscle or renal sympathetic nerve activity (10,36,38,54), and in the presence of intact baroreflexes these responses are augmented (37,38,40).…”

Section: Discussionmentioning

confidence: 99%

“…Impairment of the baroreflex would produce inadequate homeostatic responses to the changing posture that lead to orthostatic hypotension (6, 15, 25). Therefore, neural interaction between VSR and baroreflexes are important in understanding the hemodynamic changes that occur during postural changes.Previous neuroanatomical and electrophysiological studies have shown direct projections from vestibular nuclei to brain stem nuclei regulating cardiovascular functions including nucleus tractus solitarius (NTS), dorsal motor vagal nucleus, nucleus ambiguous, caudal ventrolateral medulla (CVLM), and rostral ventrolateral medulla (RVLM) (2,45,(51)(52)(53)55). Direct stimulation of the vestibular nerves in animals results in increased sympathetic activity to a number of vascular beds (5,23,32,54).…”

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confidence: 99%

Diminished baroreflex control of heart rate responses in otoconia-deficient C57BL/6JEi head tilt mice

Xue

Skala

Jones

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

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The maintenance of stable blood pressure during postural changes is known to involve integration of vestibular and cardiovascular central regulatory mechanisms. Sensory activity in the vestibular system plays an important role in cardiovascular regulation. The purpose of this study was to determine the role of vestibular gravity receptors in normal baroreflex function. Baroreflex heart rate (HR) responses to changes in blood pressure (BP) in otoconia-deficient head tilt (het) mice (n = 8) were compared with their wild-type littermates (n = 12). The study was carried out in conscious male mice chronically implanted with arterial and venous catheters for recording BP and HR and for the infusion of vasoactive drugs. Resting HR was higher in the het mice (661 +/- 13 beats/min) than in the wild-type mice (579 +/- 20 beats/min). BP was comparable in the het (113 +/- 4 mmHg) and wild-type mice (104 +/- 4 mmHg). The slopes of reflex decreases in HR in response to phenylephrine (PE) were blunted in the het mice (-5.5 +/- 1.5 beats x min(-1) x mmHg(-1)) compared with the wild-type mice (-8.5 +/- 0.9 beats x min(-1) x mmHg(-1)). Likewise, reflex tachycardic responses to decreases in BP with sodium nitroprusside (SNP) were significantly blunted in the het mice (-0.8 +/- 0.3 beats x min(-1) x mmHg(-1)) versus the wild-type mice (-2.2 +/- 0.6 beats x min(-1) x mmHg(-1)). Frequency-domain analysis of the HR variability suggests that under resting conditions, parasympathetic contribution was lower in the het versus wild-type mice. Mapping of the expression of immediate-early gene product, c-Fos, in forebrain and brain stem nuclei in response to a BP challenge showed no differences between the wild-type and het mice. These results suggest that tonic activity of gravity receptors modulates and is required for normal function of the cardiac baroreflexes.

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Processing of vestibular and other inputs by the caudal ventrolateral medullary reticular formation

Cited by 21 publications

References 0 publications

Responses of neurons in the caudal medullary lateral tegmental field to visceral inputs and vestibular stimulation in vertical planes

Responses of neurons in the caudal medullary lateral tegmental field to visceral inputs and vestibular stimulation in vertical planes

Rhythmic activity of neurons in the rostral ventrolateral medulla of conscious cats: effect of removal of vestibular inputs

Diminished baroreflex control of heart rate responses in otoconia-deficient C57BL/6JEi head tilt mice

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