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Neurophysiology of the Developing Taste System
Published in Robert H. Cagan, Neural Mechanisms in Taste, 2020
Robert M. Bradley, Charlotte M. Mistretta
There are similarities in the solitary nucleus results from the rat and developing sheep. In sheep fetuses younger than 114 d of gestation, only NH4Cl, KCl, and citric acid were effective stimuli. There were no responses to stimulation of the tongue with NaCl or LiCl in fetuses younger than 114 d. Gradually, in older fetuses and lambs, responses to NaCl and LiCl occurred more frequently (Figure 10). It is possible to record small magnitude chorda tympani nerve responses to NaCl and LiCl before 114 d;15 therefore, as in the rat, the first-order cells respond to chemical stimulation of the tongue before responses can be recorded from second-order cells. Moreover, in sheep there is a progressive decrease in the latency of solitary nucleus responses to NH4Cl and KCl and an increase in the duration of the response discharge as a function of gestational age.
Serotonergic and Catecholaminergic Mechanisms for Baroreflex Regulation in the NTS
Published in I. Robin A. Barraco, Nucleus of the Solitary Tract, 2019
Injection into the NTS of 5-HT (0.2 nmol) reduced renal nerve firing, and this sympathetic inhibition was invariably followed by corresponding decreases in mean pressure and heart rate (Figure 1). Similar injections into the NTS of either the vehicle alone or 0.2 nmol norepinephrine were ineffective (Table 1). By contrast, upon injecting 5-HT either as larger, 2-nmol doses into the NTS, or as standard 0.2-nmol doses into the dorsal vagal nucleus, mean pressure was unaffected, but heart rate and renal nerve activity were slightly reduced. Injection sites in brains from these rats were located mainly in the dorsal solitary nucleus, 0.5 mm lateral to the midline and 0.5 mm below the medullary surface, at the level of the caudal tip of the area postrema. We concluded, therefore, that the depressor, brady-cardic, and sympathoinhibitory responses elicited by injecting 0.2 nmol of 5-HT into the NTS were specific for both the 5-HT dose and the sites of injection.
Neural Regulation
Published in Stephen W. Carmichael, Susan L. Stoddard, The Adrenal Medulla 1986 - 1988, 2017
Stephen W. Carmichael, Susan L. Stoddard
Sved (1986) reported that bilateral lesions of the solitary nucleus produced hypertension in unanesthetized, freely moving rats along with at least 10-fold increases in peripheral norepinephrine and epinephrine concentrations as well as increases in vasopressin. In the lesioned animals, an acute decrease in blood pressure was elicited by blockade of either the sympathoadrenal system by chlorisondamine (a ganglionic blocking agent) or of vasopressin by the administration of an antagonist. Such observations suggest that the sympathoadrenal system, interacting with vasopressin and the renin-angiotensin system, is involved in the mediation of hypertension produced by bilateral lesions of the solitary nucleus.
Communication between the gut microbiota and peripheral nervous system in health and chronic disease
Published in Gut Microbes, 2022
Tyler M. Cook, Virginie Mansuy-Aubert
As illustrated in Fig.1 and 2, vagal and spinal afferent neurons innervate the digestive tract, monitoring mechanical, chemical, thermal, and nociceptive signals related to the diet and microbiota.40–45 It is important to note that some enteric neurons are also characterized as afferent and they are labeled as “intrinsic”, while spinal and vagal neurons which originate outside of the gut are “extrinsic”. Vagal afferent neurons transmit signals up from the viscera, their cell bodies are located in the nodose ganglia (NG), and they synapse into the solitary nucleus (NTS) in the brainstem (Figure 2). The NTS integrates vagal afferent signals and relays the information up to higher brain regions such as the hypothalamus, or reflexes back down to the dorsal motor nuclei of the brainstem where vagal efferent neurons project out to effector organs.46 Spinal neurons, with cell bodies in the dorsal root ganglia (DRG), project into the dorsal horn of the spinal cord. These signals are relayed up to the brain and integrated, or they induce reflex activation of motor neurons which may bypass the brain. The spinal nerves can be subdivided into 5 divisions: cervical, thoracic, lumbar, sacral, and coccygeal, based on their projections into and out of the vertebrae.
Emerging drugs for the prevention of migraine
Published in Expert Opinion on Emerging Drugs, 2021
Oyindamola Ogunlaja, Nazia Karsan, Peter Goadsby
PACAP is widely distributed; it is found in the peripheral and central nervous systems, as well as in exocrine and endocrine tissues in the respiratory, gastrointestinal, endocrine and reproductive systems [42–47]. Therefore, it is implicated in a wide range of functions. In the nervous system, it acts as an immunomodulator, neuromodulator, and neurotransmitter [48]. There is a saturable PACAP uptake mechanism into the brain [49], which offers an interesting dimension when considering a site of action. Both PACAP-38 fibers and PAC1 receptors are located in areas associated with migraine pathophysiology, specifically the paraventricular nucleus of the hypothalamus, locus coeruleus, ventrolateral periaqueductal gray, solitary nucleus, trigeminal nucleus caudalis, and the trigeminal ganglion [39,50–54]. Moreover, trigeminocervical neurons responding to a trigeminovascular nociceptive stimulus are modulated by PACAP-based mechanisms [55].
Minimal acute toxicity from proton beam therapy for major salivary gland cancer
Published in Acta Oncologica, 2020
Michael Chuong, John Bryant, William Hartsell, Gary Larson, Shahed Badiyan, George E. Laramore, Sanford Katz, Henry Tsai, Carlos Vargas
Although we were not able to perform a formal dosimetric analysis it is reasonable to expect that PBT achieved superior sparing of the brain and brainstem compared to what would have been delivered with IMRT, and that this contributed to our favorable toxicity findings [13]. Kocak-Uzel et al. demonstrated that higher mean dose to the area postrema, brainstem, dorsal vagal complex, medulla oblongata, solitary nucleus, oropharyngeal mucosa and whole brain was significantly associated with clinically significant nausea and vomiting among 130 head and neck cancer patients treated with IMRT [15]. In fact, the percent-volume of these structures receiving 20–40 Gy was more strongly associated with ematogenesis than higher doses. Several other publications have also demonstrated that reduced mean and low-dose exposure to substructures of the brain and brainstem minimizes the probability of not only ematogenesis [16–19], but also potentially severe fatigue [20–22]. Lastly, dysgeusia is among the most influential factors that negatively affects quality of life [23] and has been significantly correlated with mean oral cavity dose [9,10], which is routinely <1 Gy with PBT compared to >20 Gy with IMRT among ipsilateral head and neck patients [13].