Bill J. Yates - US grants

Electrical stimulation of the vestibular nerve produces changes in sympa- thetic outflow and blood pressure (Uchino et al., 1970; Ishikawa et al., 1979). In addition, vestibular lesions affect orthostatic reflexes (cardiovascular responses to a change in body position): such lesions greatly impair blood pressure compensation to 60 deg tilt in cats (Doba and Reis, 1974; Huang et al., 1977). The occurrence of vestibule-sympathetic reflexes which counteract orthostatic hypotension is not unexpected; vestibular receptors inform the nervous system about changes in head position, and thus changes in posture. Since the physiological response to orthostatic hypotension is an increase in sympathetic outflow (Gauer and Thron, 1965), it seems practical for inputs which signal a change in posture to influence the autonomic nervous system. Preliminary studies revealed that neurons in at least two brainstem regions known to contain a high density of cardioregulatory neurons, the ventrolateral medulla and the paramedian reticular nucleus, receive vestibular inputs. In addition, inputs from the carotid sinus and labyrinth were shown to converge on single units in these regions. The proposed studies will utilize both electrical and natural vestibular stimulation and will analyze vestibular inputs to brainstem cardioregulatory neurons as well as vestibular-elicited reflexes recorded from sympathetic nerves. These experiments will show which descending pathways convey vestibular signals to sympathetic preganglionic neurons and characterize the inputs to these pathways. This information will reveal which peripheral endorgans (semicircular canals or otolith organs) are important in producing ventibulo-sympathetic reflexes. In addition, the possibility that somatic inputs from the hindlimb converge on neurons that are part of the vestibulo-sympathetic pathway will be considered.

The primary goal of the proposed subproject is to examine the role of noradrenergic transmitters in the function of the vestibulo-spinal systems. Previous work has shown that there are noradrenergic inputs to portions of the vestibular nuclei, reticular formation, and spinal motor neurons, all of which are presumed to affect vestibulo-spinal reflexes. The first aim seeks to address the issue of whether regions of the vestibular nuclei that contain vestibulo-spinal projecting neurons receive noradrenergic inputs in cats. Immunohistochemical reactions of brainstem sections through the VNC will be performed for two precursor enzymes of norepinephrine (tyrosine hydroxylase and dopamine-beta-hydroxylase) and for the enzyme phenylethanol-N-methyltransferase as a control against epinephrine. The second aim attempts to determine which noradrenergic producing cell groups provide inputs to the vestibular nuclei and whether these cell groups in turn receive reciprocal input from the vestibular nuclei. Neural tracing studies in combination with immunohistochemistry for tyrosine-beta-hydroxylase will be performed to identify the regional projections between the noradrenergic cell groups and the vestibular nuclei. The third aim proposes to determine if the noradrenergic cells that project to the spinal cord, vestibular nuclei and/or reticular formation receive vestibular signals. Electrophysiological recordings from noradrenergic cells will be performed and the cell?s projections identified by antidromic invasion. The response to vestibular and neck stimulation will be examined. The fourth aim is to address the effects of noradrenergic transmitters upon the vestibulo-spinal reflexes. EMG recordings from the triceps muscle will be performed during vestibular stimulation, with application of norepinephrine, as well as noradrenergic agonists and antagonists into the lateral vestibular nucleus.

DESCRIPTION (provided by applicant): Vomiting is a consequence of a stereotyped pattern of co-contractions of the diaphragm and abdominal muscles that generate high intragastric pressures. The goal of this application is to decipher the processing of vestibular inputs by the medullary circuitry that produces vomiting, and to determine how this signal processing is affected by other inputs that can elicit emesis. Specific Aim 1 will map the locations of neurons activated during vomiting and accompanying nausea elicited by stimulation of vestibular receptors and compare the sites to those activated during emesis triggered by gastrointestinal (GI) inputs. Specific Aim 2 will employ inactivation of subregions of the vestibular nuclei (VN) to identify the area that is essential for producing vestibular-elicited vomiting. Once the brainstem regions containing neurons that participate in generating vomiting are established, subsequent experiments will ascertain the responses of cells in these areas to natural vestibular stimulation added to activation of GI receptors. Specific Aim 3 will consider neuronal responses in nucleus tractus solitarius (NTS) and the VN, which respectively receive GI and labyrinthine inputs from the periphery that can induce emesis and nausea. Specific Aim 4A will determine the responses of neurons in a region that is a component of the vomiting pattern generator: the dorsal medullary lateral tegmental field (LTF) positioned between NTS and the retrofacial nucleus. Specific Aim 4B will consider the processing of signals by PBN, which is involved in transmitting viscerosensory signals to the forebrain, to provide insights into how integration of vestibular and visceral inputs together differs in this region critical for generating nausea and medullary elements that produce vomiting. At the conclusion of Aim 4 we will have thoroughly sampled the responses of neurons to labyrinthine stimulation in the major brainstem areas known to participate in triggering and coordinating vomiting and accompanying affective responses. We will also systematically determine how vestibular signals are transformed in the emetic circuit as they are relayed from the VN to NTS and finally to LTF and the PBN. Furthermore, we will ascertain how the presence of other emetic signals affects the processing of labyrinthine inputs, and whether this processing is profoundly altered immediately before or after an episode of vomiting. As such, the studies will provide insights into the signal integration responsible for the generation of motion sickness.

[unreadable] DESCRIPTION (provided by applicant): Head direction cells (HDC) located in several regions of the brain, including the anterior dorsal nucleus of the thalamus, postsubiculum, and lateral mammillary nuclei, provide the neural substrate for the determination of directional heading. Although activity of HDC is influenced by various sensory signals and internally generated cues, lesion studies and some anatomical and physiological evidence suggest that vestibular inputs are critical for the maintenance of directional sensitivity of these cells. In addition, relatively direct pathways have been proposed that could relay vestibular signals to brain areas containing HDC. However, vestibular inputs must be transformed considerably in order to signal head direction, and it is uncertain whether the simple circuitry that has been postulated to mediate vestibular influences on HDC can accomplish this transformation of signals. One purpose of the proposed research is to establish whether a relatively direct pathway links the vestibular nuclei with brain areas containing HDC. Specific Aim 1 tests the hypothesis that injection of the retrograde transneuronal tracer pseudorabies virus into two areas containing HDC, the anterior dorsal nucleus of the thalamus and lateral mammillary nuclei, results in labeling of neurons in the vestibular nuclei within short survival times, suggesting that only a few synapses separate HDC from vestibular nucleus neurons. Furthermore, definitive physiological studies have not been conducted to determine whether HDC respond similarly during active head rotations and passive rotations of the animal's body that activate labyrinthine receptors. If labyrinthine signals contribute to the directional sensitivity of HDC as substantially as suggested by prior lesion studies, then these cells should respond to high-frequency passive horizontal rotations that powerfully activate semicircular canal afferents. Specific Aim 2 tests the hypothesis that HDC have similar responses to active head rotations in the horizontal plane and passive rotations imposed using a turntable, including rotations delivered in the dark such that the predominant sensory information available is from the labyrinth. These experiments will establish whether the vestibular system plays a direct and powerful role in determining directional heading, and should advance understanding of the neural underpinnings of navigation. This work may also provide insights into potential effects of peripheral and central vestibular lesions on spatial cognition in humans. [unreadable] [unreadable]

? DESCRIPTION (provided by applicant): This application requests funds to continue a training program in auditory and vestibular neuroscience at the University of Pittsburgh. Resources to support two predoctoral and two postdoctoral trainees per year are requested. While considerable progress has been made in identifying the genetic and molecular bases of inner ear deficits, the biological bases of centrally-generated hearing and balance disorders, which are increasingly recognized as major contributors to auditory and vestibular dysfunction, are still poorly understood. The proposed program is intended to generate auditory and vestibular scientists who can address these problems, through training in basic neuroscience and the clinical aspects of hearing and balance disorders. A group of 15 preceptors who are committed to auditory and vestibular neuroscience research and to recruit and educate outstanding pre- and postdoctoral fellows will comprise the training faculty. The research methodology employed by the preceptors ranges from cellular and molecular to developmental to systems and cognition using a variety of model systems, ensuring that trainees use are exposed to the breadth and variety of technical and conceptual approaches that define modern research in the field. In addition to conducting research, trainees attend monthly research seminars, and participate in a series of professional development workshops that provide explicit training in such survival skills as written and oral communication, obtaining jobs and grants, teaching, and managing a research lab. All trainees must submit a fellowship application as part of the program, the writing of which will be facilitated by periodic meetings with a local committee that provides advice and guidance, as well as utilizing grant-writing workshops provided by the office of academic career development. Training in the responsible scientific conduct is an integral part of the professional development workshops, the core curriculum, and laboratory training. A solid structure is in place to mentor the trainees and monitor their progress through the program.

DESCRIPTION (provided by applicant): Nausea and vomiting are common highly aversive experiences for patients with gastrointestinal disease and result in reductions of appetite, qualit of life, and adherence to medications with these side effects. Progress in understanding the biology and treatment of nausea and vomiting has been slow partly because there is currently no focused scientific meeting to discuss and collaborate on these research topics. The current R13 application is a request to support a comprehensive scientific conference on the mechanisms of nausea and vomiting, International Conference on Nausea and Vomiting 2013, to be held at University of Pittsburgh (October 3-4, 2013). This conference will substantially contribute to the goal of the National Commission on Digestive Diseases to understand the noxious visceral signaling causing nausea and vomiting related to gastric neuro-electrical and/or motor dysfunction and the bi-directional brain-gut interactions. There are four objectives of the conference: 1) Provide a forum for cross-disciplinary exchange of ideas to advance research on the biological mechanisms for nausea and vomiting, 2) Foster interactions for young investigators to present research findings and connect with laboratories and more senior investigators working in the field of nausea and vomiting research, 3) Offer a forum where scientists and clinicians who treat patients with nausea and vomiting can exchange information, and 4) Produce an overview and discussion of the major unresolved questions in nausea and vomiting biology and provide the latest methodology. The conference will include five primary sessions: 1) Personalized Medicine and Genetics; 2) Gastroparesis and Cyclic Vomiting Syndrome; 3) Vestibular and Gastrointestinal Integration; 4) Assessment and Control of Nausea; and 5) Cellular Biology and Future Directions. Speakers will present cutting edge research on nausea and vomiting related to gastroparesis, pregnancy, cyclic vomiting syndrome, motion sickness, and drug responses (chemotherapy, opioid analgesics) using genetic, electrophysiological, neuroimaging, and electronic patient reporting approaches. A scientific poster session featuring young investigators will also be provided. The proceedings of the conference will be published in a peer-reviewed journal: Experimental Brain Research. Conference attendees will primarily include scientists (neuroscience, nutrition, and pharmacology), physicians (gastroenterology, oncology, and anesthesiology), and other heathcare providers (nurses, nutritionists). Emphasis will be placed on attendance by early stage investigator faculty and trainees to facilitate the next generation of researchers.

? DESCRIPTION (provided by applicant): Nausea and vomiting are common highly aversive experiences for patients with gastrointestinal disease and result in reductions of appetite, quality of life, and adherence to medications with these side effects. Progress in understanding the biology and treatment of nausea and vomiting has been slow partly because there is currently no focused scientific meeting to discuss and collaborate on these research topics. The current R13 application is a request to support a comprehensive scientific conference on the mechanisms of nausea and vomiting, Biology and Control of Nausea and Vomiting 2015, to be held at University of Pittsburgh (October 23-24, 2015). This conference will substantially contribute to the goal of the National Commission on Digestive Diseases to understand the noxious visceral signaling causing nausea and vomiting related to gastric neuro- electrical and/or motor dysfunction and the bi-directional brain-gut interactions. There are five objectives of the conference: 1) Provide a forum for cross-disciplinary exchange of ideas to advance research on the biological mechanisms for nausea and vomiting; 2) Foster interactions for early-stage investigators to present research findings and connect with laboratories and more senior investigators working in the field of nausea and vomiting research; 3) Offer a forum where clinicians who treat patients with nausea and vomiting can exchange information; 4) Produce an overview and discussion of the major unresolved questions in nausea and vomiting biology and provide the latest methodology; and 5) Broadly disseminate the findings and consensus of the meeting in peer-review manuscripts. The conference will include six primary sessions: 1) Prodromal responses and signs of nausea; 2) Acute-to-chronic nausea and vomiting; 3) Cyclic vomiting syndrome research symposium; 4) Early-stage investigator symposium; 5) Clinical panel discussion; and 6) Cyclic vomiting syndrome adult guidelines session. Speakers will present cutting edge research on nausea and vomiting related to gastroparesis, pregnancy, cyclic vomiting syndrome, motion sickness, and drug responses (e.g., chemotherapy) using genetic, electrophysiological, neuroimaging, and patient reporting approaches. A scientific poster session will also be provided. The proceedings of the conference will be published in a peer- reviewed journal: Autonomic Neuroscience: Basic and Clinical. Conference attendees will include scientists (neuroscience, nutrition, and pharmacology), physicians (gastroenterology, oncology, and anesthesiology), and other heathcare providers (nurses, nutritionists). Emphasis will be placed on attendance by early-stage investigator faculty and trainees to facilitate the next generation of researchers.

? DESCRIPTION (provided by applicant): Two feedback mechanisms, vestibulosympathetic and baroreceptor reflexes, act in parallel to sustain stable blood pressure during changes in posture. In addition, motor planning engages feedforward autonomic responses that assure an adequate blood supply to the body during movement. However, little is known about the interactive effects of feedback and feedforward signals on the activity of brainstem neurons that control autonomic function. This grant employs neurophysiological recordings in conscious animals from brainstem neurons that regulate blood pressure, and investigates three novel concepts regarding the integrated control of vestibulosympathetic and baroreceptor reflexes. First, the gain of these responses is adjusted cognitively in accordance with the expected magnitude of an upcoming head-up tilt. Second, the gain of baroreceptor reflexes increases following a bilateral labyrinthectomy to compensate for the loss of vestibulosympathetic responses. Third, the gains of both vestibulosympathetic and baroreceptor reflexes are adjusted through inputs from the uvula, a region of the caudal cerebellar vermis. In particular, we will determine whether uvula Purkinje cells mediate cognition-related changes in the gains of vestibulosympathetic and baroreceptor reflexes, as well as plastic changes in baroreceptor reflexes when blood pressure becomes labile during postural alterations. These experiments have clinical implications. This work will ascertain whether anticipation of postural changes causes feedforward alterations in vascular resistance that prevent peripheral blood pooling and orthostatic hypotension during the ensuing movement, and whether the cerebellar vermis mediates these responses. Orthostatic hypotension becomes more prevalent during aging, which is also associated with cerebellar degeneration. The notion that aging-related cerebellar degeneration could lead to a cardiovascular disturbance that commonly results in falling and injuries has not been previously considered. The findings from these studies also have implications for other clinical conditions where cognition affects blood pressure, including anxiety and stress disorders.

Project Summary/Abstract: For decades, it has been assumed that despite the triggering stimulus, the same brainstem areas are responsible for producing nausea and emesis. However, our recent preliminary studies suggested that nausea and vomiting are complex conditions that include a variety of physiological responses that vary between individuals, and in accordance with the triggering stimulus. This grant uses synergistic approaches to characterize the divergence, convergence, and multisensory integration by brainstem neurons of vestibular and other signals that can produce emesis. Specific Aim 1 includes the first comprehensive comparison of the brainstem pathways that participate in generating nausea and emesis following the intragastric infusion of copper sulfate or presentation of vestibular stimuli to induce motion sickness. By utilizing an innovative statistical approach that we recently developed, we will identify the neural networks that are activated by these stimuli from Fos labeling patterns. We hypothesize that different brainstem networks are engaged in animals that exhibit objective changes in stomach myoelectric activity indicative of nausea following stimulation of vestibular versus gastrointestinal receptors. Specific Aims 2 and 3 respectively use neurophysiologic techniques to characterize the integration of emetic inputs by parabrachial nucleus (PBN) neurons that transmit these signals to supratentorial brain areas, and by parasympathetic preganglionic neurons (PPGNs) in the dorsal motor nucleus of the vagus (DMV) and near-by nucleus ambiguus that transmit the signals to peripheral effectors. Aim 3 will also compare the responses of PPGNs to those of neurons in two adjacent areas that play a key role in integrating these signals: nucleus tractus solitarii (NTS) and the lateral tegmental field (LTF), which comprises the brainstem ?vomiting center.? Aim 3 incorporates the first characterization of responses to vestibular stimulation of PPGNs; although these neurons coordinate the changes in gastrointestinal activity during vomiting, virtually nothing is known about modifications in their firing rate elicited by emetic stimuli. By contrasting the integration of inputs from vestibular and gastrointestinal afferents in these key groups of brainstem neurons (PPGNs and those in PBN, NTS, and LTF), we can test our overall hypothesis that signals that elicit vomiting are processed independently in the brainstem, and only converge on neurons that directly control emetic responses. Understanding how vestibular and gastrointestinal signals are transformed in brainstem emetic pathways is key to generating insights into new treatments for nausea and vomiting. At the conclusion of the proposed studies, we will have identified brainstem networks that mediate nausea and vomiting, the influences of nausea-related and emetic signals on the activity of neurons in those networks, and their differential and/or synergistic responsiveness to vestibular and gastrointestinal signals.