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María Sáez, Maya Ketzef, Javier Alegre-Cortés, Ramón Reig, Gilad Silberberg
Focal administration of pharmacological agents during in vivo recordings is a useful technique to study the functional properties of neural microcircuits. However, the lack of visual control makes this task difficult and inaccurate, especially when targeting small and deep regions where spillover to neighboring regions is likely to occur. An additional problem with recording stability arises when combining focal drug administration with in vivo intracellular recordings, which are highly sensitive to mechanical vibrations...
April 18, 2018: Neuroscience
Shiro Itoi, Miwa Suzuki, Kiyoshi Asahina, Eitaro Sawayama, Junki Nishikubo, Hikaru Oyama, Mitsuki Takei, Nanae Shiibashi, Tomohiro Takatani, Osamu Arakawa, Haruo Sugita
It is known that tetrodotoxin (TTX), also known as pufferfish toxin, is an extremely potent neurotoxin and had been detected in various taxa. However, the exact function of the toxin in TTX-bearing organisms has remained unclear. In Takifugu pufferfish species, it has been suggested that TTX is utilized to protect larvae from predators but no experimental proof exists. In the present study, we used pufferfish Takifugu alboplumbeus larvae from wild and cultured parents to determine the effects of the maternal TTX on the survival of toxic and non-toxic pufferfish larvae, respectively...
April 17, 2018: Toxicon: Official Journal of the International Society on Toxinology
Lei Xu, Dayu Li, Junjie Ding, Li Pan, Xiaoqin Ding
Nav 1.2, a member of voltage-gated sodium channels (Nav s) that are responsible for the generation and propagation of action potentials along the cell membrane, and play a vital role in the process of information transmission within the nervous system and muscle contraction, is preferentially expressed in the central nervous system. As a potent and selective blocker of Nav s, tetrodotoxin (TTX) has been extensively studied in biological and chemical sciences, whereas the detailed mechanism by which it blocks nine Nav 1 channel subtypes remain elusive...
April 19, 2018: Chemical Biology & Drug Design
Rafael Campos, Fabíola Z Mónica, Alberto Fernando Oliveira Justo, José Carlos Cogo, Edvana de Toledo Oliveira, Ronilson Agnaldo Moreno, Edson Antunes, Gilberto De Nucci
A tetrodotoxin (TTX)-resistant mechanism is responsible for the electrical field stimulation (EFS)-induced contractions and relaxations of Crotalus durissus terrificus corpora cavernosa. Here it was investigated whether this mechanism also occurs in corpora cavernosa and aortae of the non-venomous snake Pantherophis guttatus corpora cavernosa and aortae. Corpora cavernosa and aortic rings isolated from Pantherophis guttatus snake were mounted in organ bath system for isometric tension recording. EFS-induced contractions in both tissues were performed in the presence and absence of guanethidine (30 μM), phentolamine (10 μM) and tetrodotoxin (1 μM)...
2018: PloS One
Fernando R Fernandez, Bahar Rahsepar, John A White
Synaptic activity in vivo can potentially alter the integration properties of neurons. Using recordings in awake mice, we targeted somatosensory layer 2/3 pyramidal neurons and compared neuronal properties with those from slices. Pyramidal cells in vivo had lower resistance and gain values, as well as broader spikes and increased spike frequency adaptation compared to the same cells in slices. Increasing conductance in neurons using dynamic clamp to levels observed in vivo , however, did not lessen the differences between in vivo and slice conditions...
March 2018: ENeuro
Hiroaki Miyazawa, Kanoko Okumura, Kanae Hiyoshi, Kazuhiro Maruyama, Hisaya Kakinuma, Ryunosuke Amo, Hitoshi Okamoto, Kyo Yamasu, Sachiko Tsuda
Optical measurement of membrane potentials enables fast, direct and simultaneous detection of membrane potentials from a population of neurons, providing a desirable approach for functional analysis of neuronal circuits. Here, we applied recently developed genetically encoded voltage indicators, ASAP1 (Accelerated Sensor of Action Potentials 1) and QuasAr2 (Quality superior to Arch 2), to zebrafish, an ideal model system for studying neurogenesis. To achieve this, we established transgenic lines which express the voltage sensors, and showed that ASAP1 is expressed in zebrafish neurons...
April 16, 2018: Scientific Reports
S V Revenko, L N Tikhomirova, A V Nesterov, I A Tarakanov
In experiments on narcotized rats, BP in the left femoral artery as well as local electrical potential and electrical impedance of the symmetric segment of the right femoral artery were simultaneously recorded in situ with two extracellular nonpolarizable Ag/AgCl electrodes located along the artery at a distance of 3 mm from each other. The pulsatile arterial electrical potentials with amplitude of 100-200 μV and duration of about 50 msec were recorded, which coincided with the front of BP wave corrected for a 10-msec delay of the pressure transducer...
April 16, 2018: Bulletin of Experimental Biology and Medicine
Jaakko Haverinen, Minna Hassinen, Hanna Korajoki, Matti Vornanen
Na+ channel α-subunit composition of the zebrafish heart and electrophysiological properties of Na+ current (INa ) of zebrafish ventricular myocytes were examined. Eight Na+ channel α-subunits were expressed in both atrium and ventricle of the zebrafish heart. Nav 1.5Lb, an orthologue to the human Nav 1.5, was clearly the predominant isoform in both chambers representing 65.2 ± 4.1% and 83.1 ± 2.1% of all Na+ channel transcripts in atrium and ventricle, respectively. Nav 1.4b, an orthologue to human Nav 1...
April 12, 2018: Progress in Biophysics and Molecular Biology
Aubin Moutal, Li Sun, Xiaofang Yang, Wennan Li, Song Cai, Shizhen Luo, Rajesh Khanna
An understudied symptom of the genetic disorder Neurofibromatosis type 1 (NF1) is chronic idiopathic pain. We used targeted editing of Nf1 in rats to provide direct evidence of a causal relationship between neurofibromin, the protein product of the Nf1 gene, and pain responses. Our study data identified a protein-interaction network with collapsin response meditator protein 2 (CRMP2) as a node and neurofibromin, syntaxin 1A, and the N-type voltage-gated calcium (CaV2.2) channel as interaction edges. Neurofibromin uncouples CRMP2 from syntaxin 1A...
April 12, 2018: Neuroscience
P Bourée
No abstract text is available yet for this article.
February 1, 2018: Médecine et Santé Tropicales
Yang Won Min, Eun-Ju Ko, Jeong Hwan Kim, Ji Yeon Lee, Hee Cheol Kim, Woo Yong Lee, Poong-Lyul Rhee
Background/Aims: Although bisacodyl is a widely administered laxative, its underlying mechanism of action remains generally unknown. This study focuses on investigating the effects of bisacodyl on the human colon muscle contraction, and elucidating its mechanism of action. Methods: Sigmoid colon muscle strips (20 longitudinal and 18 circular muscles) were obtained from 20 subjects who underwent colectomy for colon cancer. Isometric force measurements were calculated in response to electrical field stimulation (EFS, 0...
April 30, 2018: Journal of Neurogastroenterology and Motility
Juan Prada, Manju Sasi, Corinna Martin, Sibylle Jablonka, Thomas Dandekar, Robert Blum
Local and spontaneous calcium signals play important roles in neurons and neuronal networks. Spontaneous or cell-autonomous calcium signals may be difficult to assess because they appear in an unpredictable spatiotemporal pattern and in very small neuronal loci of axons or dendrites. We developed an open source bioinformatics tool for an unbiased assessment of calcium signals in x,y-t imaging series. The tool bases its algorithm on a continuous wavelet transform-guided peak detection to identify calcium signal candidates...
March 30, 2018: PLoS Computational Biology
Dominic Gioia, Minfu Xu, Wesley Wayman, John Woodward
Channelrhodopsins are light activated ion channels used extensively over the past decade to probe the function of genetically defined neuronal populations and distinct neural circuits with high temporal and spatial precision. The widely used Channelrhodopsin-2 variant (ChR2) is an excitatory opsin that undergoes conformational changes in response to blue light, allowing non-selective passage of protons and cations across the plasma membrane thus leading to depolarization. In the addiction neuroscience field, opsins such as ChR2 provide a means to disambiguate the overlapping circuitry involved in mediating the reinforcing and aversive effects of drugs of abuse as well as to determine the plasticity that can occur in these circuits during the development of dependence...
March 23, 2018: Neuropharmacology
Xiaonan Zhang, Quentin Gaudry
Here, a new technique termed Tetrotoxin (TTX) Engineered Resistance for Probing Synapses (TERPS) is applied to test for monosynaptic connections between target neurons. The method relies on co-expression of a transgenic activator with the tetrodotoxin-resistant sodium channel, NaChBac, in a specific presynaptic neuron. Connections with putative post-synaptic partners are determined by whole-cell recordings in the presence of TTX, which blocks electrical activity in neurons that do not express NaChBac. This approach can be modified to work with any activator or calcium imaging as a reporter of connections...
February 14, 2018: Journal of Visualized Experiments: JoVE
Roberto De Gregorio, Salvatore Pulcrano, Claudia De Sanctis, Floriana Volpicelli, Ezia Guatteo, Lars von Oerthel, Emanuele Claudio Latagliata, Roberta Esposito, Rosa Maria Piscitelli, Carla Perrone-Capano, Valerio Costa, Dario Greco, Stefano Puglisi-Allegra, Marten P Smidt, Umberto di Porzio, Massimiliano Caiazzo, Nicola Biagio Mercuri, Meng Li, Gian Carlo Bellenchi
The differentiation of dopaminergic neurons requires concerted action of morphogens and transcription factors acting in a precise and well-defined time window. Very little is known about the potential role of microRNA in these events. By performing a microRNA-mRNA paired microarray screening, we identified miR-34b/c among the most upregulated microRNAs during dopaminergic differentiation. Interestingly, miR-34b/c modulates Wnt1 expression, promotes cell cycle exit, and induces dopaminergic differentiation. When combined with transcription factors ASCL1 and NURR1, miR-34b/c doubled the yield of transdifferentiated fibroblasts into dopaminergic neurons...
April 10, 2018: Stem Cell Reports
Qingjuan Hu, Yuping Li, Chao Liu, Li-Ping Huang, Lvming Zeng, Songhua Wang, Hao Song, Hailong Peng, Jianhua Huang, Chong Chen, Li-Hua Yao
Our previous work showed that polysaccharide isolated from Portulaca oleracea L. (POP) has an insulinotropic effect. The voltage-gated Na+ channel (VGSC) in the excitement phase plays an important role. This work aims to study the effect of POP on the voltage-gated Na+ channel current (INa ) and its channel dynamic characteristics in insulin-secreting β-cell line (INS-1) cells of rat. Our results revealed that POP can inhibit the amplitude of INa and improve cell survival in a concentration-dependent manner...
March 4, 2018: Biomedicine & Pharmacotherapy, Biomédecine & Pharmacothérapie
Jose Manuel Leão, Antonio Lozano-Leon, Jorge Giráldez, Óscar Vilariño, Ana Gago-Martínez
Tetrodotoxins (TTX) are a potent group of natural neurotoxins putatively produced by symbiotic microorganisms and affecting the aquatic environment. These neurotoxins have been recently found in some species of bivalves and gastropods along the European Coasts (Greece, UK, and The Netherlands) linked to the presence of high concentrations of Vibrio , in particular Vibrio parahaemolyticus . This study is focused on the evaluation of the presence of Vibrio species and TTX in bivalves (mussels, oysters, cockles, clams, scallops, and razor clams) from Galician Rias (northwest of Spain)...
March 6, 2018: Marine Drugs
Marit Poffers, Nathalie Bühne, Christine Herzog, Anja Thorenz, Rongjun Chen, Faikah Güler, Axel Hage, Andreas Leffler, Frank Echtermeyer
BACKGROUND: Voltage-gated sodium channels generate action potentials in excitable cells, but they have also been attributed noncanonical roles in nonexcitable cells. We hypothesize that voltage-gated sodium channels play a functional role during extravasation of neutrophils. METHODS: Expression of voltage-gated sodium channels was analyzed by polymerase chain reaction. Distribution of Nav1.3 was determined by immunofluorescence and flow cytometry in mouse models of ischemic heart and kidney injury...
March 6, 2018: Anesthesiology
Nozomi Ueyama, Keita Sugimoto, Yuta Kudo, Ken-Ichi Onodera, Yuko Cho, Keiichi Konoki, Toshio Nishikawa, Mari Yotsu-Yamashita
Tetrodotoxin (TTX, 1) is a potent neurotoxin that is widely found in both of terrestrial and marine animals. However, the biosynthetic pathway and genes for TTX have not yet been elucidated. Previously, we proposed that TTX originates from a monoterpene, based on the structures of cyclic guanidino compounds commonly found in toxic newts. However, these compounds have not been detected in marine organisms. Instead, a series of deoxy analogues of TTX were found in toxic marine animals. In this study, we further screened for TTX-related compounds in marine animals...
March 5, 2018: Chemistry: a European Journal
Christopher O Miles, Jane Kilcoyne, Pearse McCarron, Sabrina D Giddings, Thor Waaler, Thomas Rundberget, Ingunn A Samdal, Kjersti E Løvberg
Azaspiracids (AZAs) belong to a family of more than 50 polyether toxins originating from marine dinoflagellates such as Azadinium spinosum. All of the AZAs reported thus far contain a 21,22-dihydroxy group. Boric acid gel (BAG) can bind selectively to compounds containing vic-diols or α-hydroxycarboxylic acids via formation of reversible boronate complexes. Here we report use of BAG to selectively capture and release AZAs from extracts of blue mussels. Analysis of the extracts and BAG fractions by LC-MS showed that this procedure resulted in an excellent clean-up of the AZAs in the extract...
March 4, 2018: Journal of Agricultural and Food Chemistry
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