Characteristics of A-type voltage-gated K currents expressed on sour-sensing type III taste receptor cells in mice.

Sour taste is detected by type III taste receptor cells that generate membrane depolarization with action potentials in response to HCl applied to the apical membranes. The shape of action potentials in type III cells exhibits larger afterhyperpolarization due to activation of transient A-type voltage-gated K currents. Although action potentials play an important role in neurotransmitter release, the electrophysiological features of A-type K currents in taste buds remain unclear.

An electrophysiological method for evaluation of topical antipruritic drugs on itch-related neuronal activities in the spinal cord in hairless mice.

To evaluate the effects of antipruritic drugs, it is important to determine whether the neural responses induced by physiological itch stimuli are suppressed. Although there are several behavioral assessments for topical antipruritic drugs applied to the skin, there are few established methods at neuronal levels using in vivo electrophysiological recordings for predicting local efficacy of antipruritic drugs for cutaneous application. To establish an assessment of topical antipruritic drugs applied to skin using in vivo extracellular recording from neurons in the superficial dorsal horn, we examined the relationships between itch-related biting behavior and spinal neuronal responses elicited by intradermal injection of pruritogen serotonin (5-HT) in hairless mice.

Taste Receptor Cells Generate Oscillating Receptor Potentials by Activating G Protein-Coupled Taste Receptors.

The receptor potentials of taste receptor cells remain unclear. Here, we demonstrate that taste receptor cells generate oscillating depolarization ( = 7) with action potentials in response to sweet, bitter, umami, and salty taste substances. At a lower concentration of taste substances, taste receptor cells exhibited oscillations in membrane potentials with a low frequency and small magnitude of depolarization.

Diurnal rhythm regulates the frequency of carbachol-induced beta oscillation via inhibitory neural system in rat hippocampus.

Unlabelled: Animals have a diurnal rhythm with a cycle of approximately 1 day modulated by light information. This rhythm modulates memory performance. Relatedly, the hippocampal neural circuit has a dynamic property that can induce theta, beta, and gamma brain waves.

Slow recovery from the inactivation of voltage-gated sodium channel Nav1.3 in mouse taste receptor cells.

Action potentials play an important role in neurotransmitter release in response to taste. Here, I have investigated voltage-gated Na channels, a primary component of action potentials, in respective cell types of mouse fungiform taste bud cells (TBCs) with in situ whole-cell clamping and single-cell RT-PCR techniques. The cell types of TBCs electrophysiologically examined were determined immunohistochemically using the type III inositol 1,4,5-triphoshate receptor as a type II cell marker and synaptosomal-associated protein 25 as a type III cell marker.

Age-related electrophysiological changes in mouse taste receptor cells.

New Findings: What is the central question of this study? Loss of taste or inability to distinguish between different tastes progresses with age. The purpose was to evaluate the age-dependent changes in taste by studying the electrophysiological properties of taste receptor cells. What is the main finding and its importance? Ageing decreased the voltage-gated Na and K current densities of type III cells (sour and/or salt receptor cells) but did not affect the current densities in type II cells.

Cell-type-independent expression of inwardly rectifying potassium currents in mouse fungiform taste bud cells.

Inwardly rectifying potassium (Kir) channels play key roles in functions, including maintaining the resting membrane potential and regulating the action potential duration in excitable cells. Using in situ whole-cell recordings, we investigated Kir currents in mouse fungiform taste bud cells (TBCs) and immunologically identified the cell types (type I-III) expressing these currents. We demonstrated that Kir currents occur in a cell-type-independent manner.

Quantitative Analysis of Taste Bud Cell Numbers in the Circumvallate and Foliate Taste Buds of Mice.

A mouse single taste bud contains 10-100 taste bud cells (TBCs) in which the elongated TBCs are classified into 3 cell types (types I-III) equipped with different taste receptors. Accordingly, differences in the cell numbers and ratios of respective cell types per taste bud may affect taste-nerve responsiveness. Here, we examined the numbers of each immunoreactive cell for the type II (sweet, bitter, or umami receptor cells) and type III (sour and/or salt receptor cells) markers per taste bud in the circumvallate and foliate papillae and compared these numerical features of TBCs per taste bud to those in fungiform papilla and soft palate, which we previously reported.

A subset of taste receptor cells express biocytin-permeable channels activated by reducing extracellular Ca concentration.

Taste receptor cells (type II cells) transmit taste information to taste nerve fibres via ATP-permeable channels, including calcium homeostasis modulator (CALHM), connexin and/or pannexin1 channels, via the paracrine release of adenosine triphosphate (ATP) as a predominant transmitter. In the present study, we demonstrate that extracellular Ca -dependent biocytin-permeable channels are present in a subset of type II cells in mouse fungiform taste buds using biocytin uptake, immunohistochemistry and in situ whole-cell recordings. Type II cells were labelled with biocytin in an extracellular Ca concentration ([Ca ] )-sensitive manner.

Selective expression of muscarinic acetylcholine receptor subtype M3 by mouse type III taste bud cells.

Each taste bud cell (TBC) type responds to a different taste. Previously, we showed that an unidentified cell type(s) functionally expresses a muscarinic acetylcholine (ACh) receptor subtype, M3, and we suggested the ACh-dependent modification of its taste responsiveness. In this study, we found that M3 is expressed by type III TBCs, which is the only cell type that possesses synaptic contacts with taste nerve fibers in taste buds.

Time-dependent expression of hypertonic effects on bullfrog taste nerve responses to salts and bitter substances.

We previously showed that the hypertonicity of taste stimulating solutions modified tonic responses, the quasi-steady state component following the transient (phasic) component of each integrated taste nerve response. Here we show that the hypertonicity opens tight junctions surrounding taste receptor cells in a time-dependent manner and modifies whole taste nerve responses in bullfrogs. We increased the tonicity of stimulating solutions with non-taste substances such as urea or ethylene glycol.

Cell-type-dependent action potentials and voltage-gated currents in mouse fungiform taste buds.

Taste receptor cells fire action potentials in response to taste substances to trigger non-exocytotic neurotransmitter release in type II cells and exocytotic release in type III cells. We investigated possible differences between these action potentials fired by mouse taste receptor cells using in situ whole-cell recordings, and subsequently we identified their cell types immunologically with cell-type markers, an IP3 receptor (IP3 R3) for type II cells and a SNARE protein (SNAP-25) for type III cells. Cells not immunoreactive to these antibodies were examined as non-IRCs.

Subtype-dependent postnatal development of taste receptor cells in mouse fungiform taste buds.

Taste buds contain two types of taste receptor cells, inositol 1,4,5-triphosphate receptor type 3-immunoreactive cells (type II cells) and synaptosomal-associating protein-25-immunoreactive cells (type III cells). We investigated their postnatal development in mouse fungiform taste buds immunohistochemically and electrophysiologically. The cell density, i.

Hypertonicity augments bullfrog taste nerve responses to inorganic salts.

The tonicity of taste stimulating solutions has been usually ignored, though taste substances themselves yielded the tonicity. We investigated the effect of hypertonicity on bullfrog taste nerve responses to inorganic salts by adding nonelectrolytes such as urea and sucrose that elicited no taste nerve responses. Here, we show that hypertonicity alters bullfrog taste nerve-response magnitude and firing pattern.

Network model of chemical-sensing system inspired by mouse taste buds.

Taste buds endure extreme changes in temperature, pH, osmolarity, so on. Even though taste bud cells are replaced in a short span, they contribute to consistent taste reception. Each taste bud consists of about 50 cells whose networks are assumed to process taste information, at least preliminarily.

Dye-permeable, voltage-gated channel on mouse fungiform taste bud cells.

We show here the expression, permeability and pharmacology of a voltage-gated channel in certain taste bud cells (TBCs) which is known to be permeable to Lucifer Yellow CH (LY) and known to release ATP as a neurotransmitter in response to taste substances. LY dissolved in a 200 mM K(+)-containing solution label TBCs immunoreactive to PLCβ2, a phospholipase subtype, but not the TBC subtype immunoreactive to SNAP-25, a SNARE protein. In addition to these subtypes, LY also labelled a few of the non-immunoreactive TBCs.

Quantitative analysis of taste bud cell numbers in fungiform and soft palate taste buds of mice.

Mammalian taste bud cells (TBCs) consist of several cell types equipped with different taste receptor molecules, and hence the ratio of cell types in a taste bud constitutes the taste responses of the taste bud. Here we show that the population of immunohistochemically identified cell types per taste bud is proportional to the number of total TBCs in the taste bud or the area of the taste bud in fungiform papillae, and that the proportions differ among cell types. This result is applicable to soft palate taste buds.

Functional expression of M3, a muscarinic acetylcholine receptor subtype, in taste bud cells of mouse fungiform papillae.

Taste bud cells (TBCs) express various neurotransmitter receptors assumed to facilitate or modify taste information processing within taste buds. We investigated the functional expression of muscarinic acetylcholine receptor (mAChR) subtypes, M1-M5, in mouse fungiform TBCs. ACh applied to the basolateral membrane of TBCs elevates the intracellular Ca(2+) level in a concentration-dependent manner with the 50% effective concentration (EC(50)) of 0.

Functional expression of ionotropic purinergic receptors on mouse taste bud cells.

Neurotransmitter receptors on taste bud cells (TBCs) and taste nerve fibres are likely to contribute to taste transduction by mediating the interaction among TBCs and that between TBCs and taste nerve fibres. We investigated the functional expression of P2 receptor subtypes on TBCs of mouse fungiform papillae. Electrophysiological studies showed that 100 microm ATP applied to their basolateral membranes either depolarized or hyperpolarized a few cells per taste bud.

Effects of endomorphin on substantia gelatinosa neurons in rat spinal cord slices.

1. Whole-cell patch recordings were made from substantia gelatinosa (SG) neurons in transverse lumbar spinal cord slices of 15- to 30-day-old rats. 2.

Lucifer Yellow slows voltage-gated Na+ current inactivation in a light-dependent manner in mice.

Lucifer Yellow CH (LY), a membrane-impermeant fluorescent dye, has been used in electro-physiological studies to visualize cell morphology, with little concern about its pharmacological effects. We investigated its effects on TTX-sensitive voltage-gated Na+ channels in mouse taste bud cells and hippocampal neurons under voltage-damp conditions. LY applied inside cells irreversibly slowed the inactivation of Na+ currents upon exposure to light of usual intensities.

Optical recordings of taste responses from fungiform papillae of mouse in situ.

Single taste buds in mouse fungiform papillae consist of approximately 50 elongated cells (TBCs), where fewer than three TBCs have synaptic contacts with taste nerves. We investigated whether the non-innervated TBCs were chemosensitive using a voltage-sensitive dye, tetramethylrhodamine methyl ester (TMRM), under in situ optical recording conditions. Prior to the optical recordings, we investigated the magnitude and polarity of receptor potentials under in situ whole-cell clamp conditions.

Open channel block of NMDA receptors by conformationally restricted analogs of milnacipran and their protective effect against NMDA-induced neurotoxicity.

We investigated the blocking effect of the conformationally restricted analogs of milnacipran on NMDA receptors by recording the whole-cell currents of Xenopus oocytes injected with rat brain mRNA and the single channel currents of cultured hippocampal neurons under voltage-clamp conditions. Their protective effect against excitotoxicity was also investigated on cultured cortex neurons. All conformationally restricted analogs examined blocked activated NMDA receptors, though their structures were quite different from known NMDA receptor blockers.

IgD multiple myeloma with renal involvement: case report.

IgD multiple myeloma is a unique type of multiple myeloma which is characterized by increased serum IgD and IgD type M-component in immunoelectrophoresis. It frequently shows renal involvement but it is a rare form of myeloma. The distinctive features of IgD myeloma are the dominance in males, high frequency in younger persons, and the uncertain appearance of M-component in serum electrophoresis.

Nonsurgical embryo collection from sows with surgically shortened uteri.

To allow for the nonsurgical collection of swine embryos, the uteri of sows (n=7) were surgically shortened. A section of each uterine horn was resected to facilitate a transcervical flushing procedure. All sows with a shortened uterus exhibited natural estrus at least once after the operation.