Single-channel studies

Martin, R.J., Robertson, A.P., Bjorn, H. and Sangster, N.C. (1997) Heterogeneous levamisole receptors a single-channels study of nictotinic acetylcholine receptors from Oesophagostomum dentatum. European Journal of Pharmacology 322, 249-257. 

Peng F, Mellor IR, Williamson MS, Davies TG, Field LM, Usherwood PN (2009) Single channel study of deltamethrin interactions with wild-type and mutated rat Nav1.2 sodium channels expressed in Xenopus oocytes. Neurotoxicology 30 358-367... 

Segal We did our studies using single channel recording in part because we worried that any persistent inward current that we would see by macroscopic current recording could be dismissed as an artefact of poor clamp control of the neuron. However, Chao Alzheimer (1995) did such a study of macroscopic currents while we were doing our single-channel studies and they found a similar... 

From the 1960s onward, there was a greater interest in psychological issues, dominated by the concept of the human as a single-channel processor of information. This stimulated research into a number of areas. Studies of mental workload were concerned with the ability of humans to cope with extremely high levels of information in situations such as air traffic control. Vigilance studies, which focused on the human s role in situations with very low levels of stimulation such as radar monitoring, represented the other extreme of human performance that was considered. 

In the previous section was given the experimental demonstration of two sites. Here the steady state scheme and equations necessary to calculate the single channel currents are given. The elemental rate constants are thereby defined and related to experimentally determinable rate constants. Eyring rate theory is then used to introduce the voltage dependence to these rate constants. Having identified the experimentally required quantities, these are then derived from nuclear magnetic resonance and dielectric relaxation studies on channel incorporated into lipid bilayers. 

Biochemical studies with purified preparations incorporated into liposomes have also been performed [32,33,96-98]. Reconstituted receptors from skeletal muscle bound DHPs, PAAs and diltiazem with high affinity and in a 1 1 1 stoichiometry [97], In general, the reconstituted proteins exhibit the characteristic pharmacological properties expected for these channels. In recent studies, our laboratory has reconstituted partially purified channels into liposomes containing the Ca -sensitive fluorescent dye, fluo-3 [33,96]. These channels exhibit Ca influx that is sensitive to activation by Ca channel activators and inhibitors with affinities similar to those observed in intact cells, and the Ca influx is dependent on the establishment of a gradient in the presence of valinomycin [132]. This assay provides a convenient and rapid approach to obtaining a macroscopic picture of the activity of the channels under different conditions, while the more complex studies in lipid bilayers provide a more complete analysis of the single channel behavior. 

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