Maturation of neuron types in nucleus of solitary tract associated with functional convergence during development of taste circuits

Late fetal through postnatal development in sheep is a period of increasing convergence of afferent taste fibers onto second-order neurons in the nucleus of the solitary tract (NST). To learn whether neuron morphology alters in concert with convergence and neurophysiological development in NST, three-dimensional neuron reconstructions were made of cells in a functionally defined region of gustatory NST from Golgi preparations of the brainstem. Elongate, multipolar, and ovoid neurons were studied in fetuses from 85 days of gestation through the perinatal period (term = 147 days of gestation), to postnatal stages. Somal size and form, and dendritic complexity and extent, increased markedly from 85 to about 110 days of gestation in both of the proposed NST projection neurons, elongate and multipolar. From 130 days of gestation to postnatal ages, growth of dendrites of elongate neurons plateaued or declined, whereas dendrites of multipolar neurons apparently continued to increase in size and extent. In addition, spine density decreased on elongate neurons but remained stable on multipolar neurons. Morphological variables of ovoid cells, proposed interneurons in NST, did not alter over this later period. The data suggest that multipolar, not elongate or ovoid, neurons are logical candidates to receive the increasing afferent fiber input onto NST cells during late gestation. Also, neural activity from taste afferent fibers is more likely to have a role in altering NST neuron morphology at later, rather than earlier, developmental periods. © 1994 Wiley-Liss, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/50062/1/903450304_ftp.pd

Morphology and connectivity of parabrachial and cortical inputs to gustatory thalamus in rats

The ventroposterior medialis parvocellularis (VPMpc) nucleus of the thalamus, the thalamic relay nucleus for gustatory sensation, receives primary input from the parabrachial nucleus, and projects to the insular cortex. To reveal the unique properties of the gustatory thalamus in comparison with archetypical sensory relay nuclei, this study examines the morphology of synaptic circuitry in the VPMpc, focusing on parabrachiothalamic driver input and corticothalamic feedback. Anterogradely visualized parabrachiothalamic fibers in the VPMpc bear large swellings. At electron microscope resolution, parabrachiothalamic axons are myelinated and make large boutons, forming multiple asymmetric, adherent, and perforated synapses onto large‐caliber dendrites and dendrite initial segments. Labeled boutons contain dense‐core vesicles, and they resemble a population of terminals within the VPMpc containing calcitonin gene‐related peptide. As is typical of primary inputs to other thalamic nuclei, parabrachiothalamic terminals are over five times larger than other inputs, while constituting only 2% of all synapses. Glomeruli and triadic arrangements, characteristic features of other sensory thalamic nuclei, are not encountered. As revealed by anterograde tracer injections into the insular cortex, corticothalamic projections in the VPMpc form a dense network of fine fibers bearing small boutons. Corticothalamic terminals within the VPMpc were also observed to synapse on cells that were retrogradely filled from the same injections. The results constitute an initial survey describing unique anatomical properties of the rodent gustatory thalamus. J. Comp. Neurol. 523:139–161, 2015. © 2014 Wiley Periodicals, Inc. Using biotinylated tract tracers and light and electron microscopy, the authors provide quantitative ultrastructural characterization of two inputs that arrive to the gustatory thalamic nucleus (ventroposterior medialis parvocellularis nucleus [VPMpc]): parabrachiothalamic axons that bring the primary input, and corticothalamic axons that provide the feedback input.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/109654/1/cne23673.pd

The Cellular Mechanism for Water Detection in the Mammalian Taste System

Initiation of drinking behavior relies on both internal state and peripheral water detection. While central neural circuits regulating thirst have been well studied, it is still unclear how mammals recognize external water. Here we show that acid-sensing taste receptor cells (TRCs) that were previously suggested as the sour taste sensors also mediate taste responses to water. Genetic silencing of these TRCs abolished water-evoked responses in taste nerves. Optogenetic self-stimulation of acid-sensing TRCs in thirsty animals induced robust drinking responses toward light even without water. This behavior was only observed when animals were water-deprived but not under food- or salt-depleted conditions, indicating that the hedonic value of water-evoked responses is highly internal-state dependent. Conversely, thirsty animals lacking functional acid-sensing TRCs showed compromised discrimination between water and nonaqueous fluids. Taken together, this study revealed a function of mammalian acid-sensing TRCs that provide a cue for external water

Expression of taste receptors in Solitary Chemosensory Cells of rodent airways

<p>Abstract</p> <p>Background</p> <p>Chemical irritation of airway mucosa elicits a variety of reflex responses such as coughing, apnea, and laryngeal closure. Inhaled irritants can activate either chemosensitive free nerve endings, laryngeal taste buds or solitary chemosensory cells (SCCs). The SCC population lies in the nasal respiratory epithelium, vomeronasal organ, and larynx, as well as deeper in the airway. The objective of this study is to map the distribution of SCCs within the airways and to determine the elements of the chemosensory transduction cascade expressed in these SCCs.</p> <p>Methods</p> <p>We utilized a combination of immunohistochemistry and molecular techniques (rtPCR and in situ hybridization) on rats and transgenic mice where the Tas1R3 or TRPM5 promoter drives expression of green fluorescent protein (GFP).</p> <p>Results</p> <p>Epithelial SCCs specialized for chemoreception are distributed throughout much of the respiratory tree of rodents. These cells express elements of the taste transduction cascade, including Tas1R and Tas2R receptor molecules, α-gustducin, PLCβ2 and TrpM5. The Tas2R bitter taste receptors are present throughout the entire respiratory tract. In contrast, the Tas1R sweet/umami taste receptors are expressed by numerous SCCs in the nasal cavity, but decrease in prevalence in the trachea, and are absent in the lower airways.</p> <p>Conclusions</p> <p>Elements of the taste transduction cascade including taste receptors are expressed by SCCs distributed throughout the airways. In the nasal cavity, SCCs, expressing Tas1R and Tas2R taste receptors, mediate detection of irritants and foreign substances which trigger trigeminally-mediated protective airway reflexes. Lower in the respiratory tract, similar chemosensory cells are not related to the trigeminal nerve but may still trigger local epithelial responses to irritants. In total, SCCs should be considered chemoreceptor cells that help in preventing damage to the respiratory tract caused by inhaled irritants and pathogens.</p

Comparative gustatory responses in four species of gerbilline rodents

Integrated taste responses to chemical stimulation of the tongue were recorded from the intact chorda tympani nerve in four species of gerbils ( Meriones libycus, M. shawi, M. unguiculatus and Psammomys obesus ).Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47116/1/359_2004_Article_BF00618177.pd

三重県地域住民に対するみそ汁の減塩指導の実践についての検討

昭和55年において,三重県地域住民に対する各保健所の健康教室,集団検診などの参加者1,201世帯を対象とし,参加者に持参させたみそ汁の食塩濃度を測定した。その結果について検討をおこなった。(1)三重県下地域住民のみそ汁の食塩濃度の平均値は1.08%であったが,各保健所ともにその値に著しいバラツキがみられた。(2)上記みそ汁の適正濃度(0.8%)以上のからずき世帯率を保健所別にみた場合は,桑名では67.8%,四日市では62.5%,鈴鹿では79.5%,津では74.6%,松阪では72.8%,上野では81.2%であった。このからすぎ世帯率において,高血圧者在宅世帯と非高血圧者在宅世帯との間には相関関係はみられなかった。(3)ついで,保健所別脳血管疾患死亡率とからずき世帯率との間には相関関係は認められなかった。In 1980 having 1,201 families participated in the health school and mass examination was held by the Regional Health Centers in Mie Prefecture. And, salt concentrations of miso soup brought by those participants were measured. The results were analyzed as follows: (1) The mean concentration of salt in miso soup referring to the regional inhabitants in Mie Prefecture was 1.08%, however, the values were markedly fluctuated by Health Centers. (2) Those families in favor of the saltier taste than the adequate concentration (0.8%) of the miso soup were noted at 67.8% in Kuwana, 62.5% in Yokkaichi, 79.5% in Suzuka, 74.6% in Tsu, 72.8% in Matsuzaka and 81.2% in Ueno. Among those families of salty taste lovers, no correlation was observed between hypertension and nonhypertension. (3) When classified by Health Centers, no correlation was observed between the mortality from cerebrovascular diseases and the percentage of salty taste loving families