N. Fertig, M. George, M. Klau, C. Meyer, A. Tilke, C. Sobotta, R. Blick, J. Behrends
{"title":"Microstructured apertures in planar glass substrates for ion channel research.","authors":"N. Fertig, M. George, M. Klau, C. Meyer, A. Tilke, C. Sobotta, R. Blick, J. Behrends","doi":"10.1080/10606820308256","DOIUrl":"https://doi.org/10.1080/10606820308256","url":null,"abstract":"We have developed planar glass chip devices for patch clamp recording. Glass has several key advantages as a substrate for planar patch clamp devices. It is a good dielectric, is well-known to interact strongly with cell membranes and is also a relatively in-expensive material. In addition, it is optically neutral. However, microstructuring processes for glass are less well established than those for silicon-based substrates. We have used ion-track etching techniques to produce micron-sized apertures into borosilicate and quartz-glass coverslips. These apertures, which can be easily produced in arrays, have been used for high resolution recording of single ion channels as well as for whole-cell current recordings from mammalian cell lines. An additional attractive application that is greatly facilitated by the combination of planar geometry with the optical neutrality of the substrate is single-molecule fluorescence recording with simultaneous single-channel measurements.","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"26 1","pages":"29-40"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84021785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Structure/activity relationships of M2 muscarinic allosteric modulators.","authors":"K. Mohr, C. Tränkle, U. Holzgrabe","doi":"10.3109/10606820308264","DOIUrl":"https://doi.org/10.3109/10606820308264","url":null,"abstract":"Allosteric modulation of G protein-coupled receptors has been intensively studied at muscarinic acetylcholine receptors. Findings made with archetypal allosteric agents such as gallamine, alcuronium, and bis(ammonio)alkane-type agents revealed that binding of orthosteric ligands that attach to the acetylcholine site can be allosterically decreased or increased or left unaltered in a subtype-selective fashion. Analyses of structure/activity relationships (SARs) help to elucidate the molecular events underlying the allosteric action and they may pilot the development of new allosteric agents with improved properties and therapeutic perspectives. With a focus on SARs, this review illustrates the principles of muscarinic allosteric interactions, gives an overview of SARs in congeners of archetypal allosteric agents, and considers the topology of M(2) muscarinic allosteric interactions that are characterized by divergent binding modes.","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"1 1","pages":"229-40"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91326010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Willumsen, M. Bech, S. Olesen, B. Jensen, Mads P. G. Korsgaard, P. Christophersen
{"title":"High throughput electrophysiology: new perspectives for ion channel drug discovery.","authors":"N. Willumsen, M. Bech, S. Olesen, B. Jensen, Mads P. G. Korsgaard, P. Christophersen","doi":"10.3109/10606820308259","DOIUrl":"https://doi.org/10.3109/10606820308259","url":null,"abstract":"Proper function of ion channels is crucial for all living cells. Ion channel dysfunction may lead to a number of diseases, so-called channelopathies, and a number of common diseases, including epilepsy, arrhythmia, and type II diabetes, are primarily treated by drugs that modulate ion channels. A cornerstone in current drug discovery is high throughput screening assays which allow examination of the activity of specific ion channels though only to a limited extent. Conventional patch clamp remains the sole technique with sufficiently high time resolution and sensitivity required for precise and direct characterization of ion channel properties. However, patch clamp is a slow, labor-intensive, and thus expensive, technique. New techniques combining the reliability and high information content of patch clamping with the virtues of high throughput philosophy are emerging and predicted to make a number of ion channel targets accessible for drug screening. Specifically, genuine HTS parallel processing techniques based on arrays of planar silicon chips are being developed, but also lower throughput sequential techniques may be of value in compound screening, lead optimization, and safety screening. The introduction of new powerful HTS electrophysiological techniques is predicted to cause a revolution in ion channel drug discovery.","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"66 1","pages":"3-12"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88876552","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Katrin Schnizler, Mike Küster, Christoph Methfessel, Michael Fejtl
{"title":"The roboocyte: automated cDNA/mRNA injection and subsequent TEVC recording on Xenopus oocytes in 96-well microtiter plates.","authors":"Katrin Schnizler, Mike Küster, Christoph Methfessel, Michael Fejtl","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Membrane-bound neurotransmitter receptors and ion channels are among the most numerous and important drug targets, and electrophysiological methods are the gold standard for the study of their functional properties and their response to drugs. However, electrophysiological measurements are usually performed one at a time by highly skilled individuals, and secondary functional screening is often hampered by this lack of throughput. Accordingly, the use of automated procedures to increase the efficiency of electrophysiological techniques is of great interest. Among the many different electrophysiological techniques that have been described, two electrode voltage clamp recording (TEVC) from Xenopus oocytes seems particularly suitable for the implementation of automated measurement systems. Here, we describe a workstation that was expressly developed for this purpose. The Roboocyte is the first (and the only currently available) instrument that automatically performs both cDNA (or mRNA) injection and subsequent TEVC recording on Xenopus oocytes plated in a standard 96-well microtiter plate. This paper describes the scientific background of the oocyte expression system for drug screening and the development of the Roboocyte. Then, some technical details of the Roboocyte system are presented and, finally, results obtained with the Roboocyte are discussed with regard to increased throughput compared with manually performed experiments. Further information can be obtained at www.roboocyte.com.</p>","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"9 1","pages":"41-8"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22453419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Skjalg Bruheim, Kurt A Krobert, Kjetil Wessel Andressen, Finn Olav Levy
{"title":"Unaltered agonist potency upon inducible 5-HT7(a) but not 5-HT4(b) receptor expression indicates agonist-independent association of 5-HT7(a) receptor and Gs.","authors":"Skjalg Bruheim, Kurt A Krobert, Kjetil Wessel Andressen, Finn Olav Levy","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>We compared adenylyl cyclase (AC) activation by the G protein-coupled human serotonin (5-HT) receptors 5-HT4(b) and 5-HT7(a) using an ecdysone-inducible expression system, which allowed for reproducible expression of increasing receptor densities in clonal HEK293 (EcR293) cell lines. Low constitutive expression of receptors (2-70 fmol/mg protein) was observed and could be titrated up to 50-200-fold (approximately 400-7000 fmol/mg protein) by the ecdysone analogue ponasterone A. Although 5-HT-stimulated AC activity increased with receptor density, interclonal variation precluded comparisons of coupling efficiency. Interestingly, the potency of 5-HT to stimulate AC increased with increasing receptor density only in clones expressing 5-HT4(b) receptors. The potency for 5-HT did not change in clones expressing 5-HT7(a) receptors, even though 5-HT-stimulated AC activity approached asymptotic levels. This indicates that potency of 5-HT for stimulation of AC through the 5-HT7(a) receptor is independent of receptor-Gs stoichiometry and is consistent with a model where the 5-HT7(a) receptors are tightly associated with G protein, independent of agonist binding. This supports the existence of a complex between inactive receptor and G protein, as predicted by the cubic ternary complex model. In such a system, spare receptors do not lead to increased potency of an agonist with increased receptor density.</p>","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"9 2","pages":"107-16"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22529267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Accessory proteins for G protein-signaling systems: activators of G protein signaling and other nonreceptor proteins influencing the activation state of G proteins.","authors":"Joe B Blumer, Stephen M Lanier","doi":"","DOIUrl":"","url":null,"abstract":"<p><p>Heterotrimeric G proteins are key transducers for signal transfer from outside of the cell. In addition to their regulation by the superfamily of G protein-coupled receptors, many if not all of the subtypes of heterotrimeric G proteins are also regulated by additional accessory proteins that influence guanine nucleotide binding and/or hydrolysis or subunit interactions. Activators of G protein signaling (AGS1-3) refer to a functionally defined group of proteins that activate G protein-signaling systems in the absence of a classical G protein-coupled receptor. AGS and related proteins provide unexpected insights into the regulation of the G protein activation/deactivation cycle and the functional roles of G proteins. These proteins likely play important roles in the generation of signaling complexes, the positioning of signaling proteins within the cell, and in biological roles of G proteins unrelated to a cell surface receptor. As such, these proteins and the concepts advanced with their discovery provide unexpected avenues for therapeutics and understanding disease mechanisms.</p>","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"9 3","pages":"195-204"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"22409852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Edward F Domino, Lisong Ni, Francis Colpaert, Marc Marien
{"title":"Effects of (+/-)-idazoxan alone and in combination with L-DOPA methyl ester in MPTP-induced hemiparkinsonian monkeys.","authors":"Edward F Domino, Lisong Ni, Francis Colpaert, Marc Marien","doi":"10.3109/713745180","DOIUrl":"https://doi.org/10.3109/713745180","url":null,"abstract":"<p><p>The effects of a combination of the alpha2-adrenergic receptor antagonist (+/-)-idazoxan with L-DOPA methyl ester were examined in three of four female adult monkeys (Macaca nemestrina) rendered hemiparkinsonian with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). (+/-)-Idazoxan (0.16, 0.63, and 1.0 mg/kg) was given i.m. 10 min before L-DOPA methyl ester (12.5 mg/kg). (+/-)-Idazoxan reduced the maximum peak of contralateral circling elicited during the first hour following injection of L-DOPA methyl ester, but prolonged the duration of the circling response up to 50% (p < 0.05). The data support a role for alpha2-adrenergic receptor mechanisms in modulating the effects of L-DOPA on nigrostriatal dopamine function in the MPTP monkey model of hemiparkinsonism.</p>","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"9 5","pages":"335-8"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/713745180","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24014305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Przemyslaw Nowak, Lukasz Labus, Joanna Stabryla, Artur Durczok, Ryszard Brus, Joanna Nowicka, Jashovam Shani
{"title":"Biogenic amines in striatum of rats that had been treated with ethanol, and their brains later stored in different temperatures.","authors":"Przemyslaw Nowak, Lukasz Labus, Joanna Stabryla, Artur Durczok, Ryszard Brus, Joanna Nowicka, Jashovam Shani","doi":"10.3109/713745172","DOIUrl":"https://doi.org/10.3109/713745172","url":null,"abstract":"<p><p>The purpose of this study was to investigate how ethanol pretreatment and storage temperatures of brain striatum affect levels of biogenic amines in this tissue. Adult Wistar male rats were injected with 25% ethanol (5.0 g/kg i.p.) while the control rats were administered i.p. with the same volume of saline. Two hours later the rats were decapitated, their brains removed, and the striatum separated. Each striatum was divided into three parts: one part was immediately frozen on dry ice and kept at -70 degrees C; a second fragment was kept in a household refrigerator (+4 degrees C); and the third fragment was kept at +22 degrees C. Twenty-four hours later, levels of DA, DOPAC, HVA, 3-MT, 5-HT, and 5-HIAA in the striatum were assayed by HPLC/ED. Immediately after decapitation; ethanol levels were assayed in the serum of ethanol-pretreated and saline-pretreated rats using gas chromatography. Our results indicate that levels of striatal DA, DOPAC, and HVA in saline-pretreated rats decreased significantly when the storage temperature of the striatum was raised from -70 degrees C, through +4 degrees C, to +22 degrees C, while levels of striatal 5-HT and 5-HIAA remained constant within the temperature range tested and levels of 3-MT fluctuated. In ethanol-pretreated rats, striatal levels of DOPAC, HVA, and 5-HIAA were increased in all three storage temperatures, while levels of DA, 5-HT, and 3-MT were decreased in those temperatures. Those decreases were most profound in striatal samples kept at +22 degrees C. We conclude that concern about possible interactions between drugs and biogenic amines should be exercised.</p>","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"9 5","pages":"339-42"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/713745172","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24014306","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Melatonin for the treatment of disorders in circadian rhythm and sleep: could it form a basis for medication?","authors":"Isaac Nir","doi":"10.3109/714041018","DOIUrl":"https://doi.org/10.3109/714041018","url":null,"abstract":"<p><p>The various aspects of the existing knowledge on the physiological role of melatonin and its mode of action in circadian rhythms and sleep are presented. Furthermore, the possibility of its clinical application in maintenance of sleep under regular and environmental changes is discussed.</p>","PeriodicalId":20928,"journal":{"name":"Receptors & channels","volume":"9 6","pages":"379-85"},"PeriodicalIF":0.0,"publicationDate":"2003-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.3109/714041018","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"24144765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}