{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T06:45:05Z","timestamp":1773384305665,"version":"3.50.1"},"reference-count":20,"publisher":"American Physiological Society","issue":"4","content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Advances in Physiology Education"],"published-print":{"date-parts":[[2002,12]]},"abstract":"<jats:p> Ion channels open and close in a stochastic fashion, following the laws of probability. However, distinct from tossing a coin or a die, the probability of finding the channel closed or open is not a fixed number but can be modified (i.e., we can cheat) by some external stimulus, such as the voltage. Single-channel records can be obtained using the appropriate electrophysiological technique (e.g., patch clamp), and from these records the open probability and the channel conductance can be calculated. Gathering these parameters from a membrane containing many channels is not straightforward, as the macroscopic current I = iNP<jats:sub>o<\/jats:sub>, where i is the single-channel current, N the number of channels, and P<jats:sub>o<\/jats:sub> the probability of finding the channel open, cannot be split into its individual components. In this tutorial, using the probabilistic nature of ion channels, we discuss in detail how i, N, and P<jats:sub>o max<\/jats:sub> (the maximum open probability) can be obtained using fluctuation (nonstationary noise) analysis (Sigworth FJ. G Gen Physiol 307: 97\u2013129, 1980). We also analyze the sources of possible artifacts in the determination of i and N, such as channel rundown, inadequate filtering, and limited resolution of digital data acquisition by use of a simulation computer program (available at www.cecs.cl ). <\/jats:p>","DOI":"10.1152\/advan.00006.2002","type":"journal-article","created":{"date-parts":[[2015,2,27]],"date-time":"2015-02-27T20:07:54Z","timestamp":1425067674000},"page":"327-341","source":"Crossref","is-referenced-by-count":112,"title":["COUNTING CHANNELS: A TUTORIAL GUIDE ON ION CHANNEL FLUCTUATION ANALYSIS"],"prefix":"10.1152","volume":"26","author":[{"given":"Osvaldo","family":"Alvarez","sequence":"first","affiliation":[{"name":"Centro de Estudios Cient\u00edficos, Valdivia"},{"name":"Departamento de Biolog\u00eda, Facultad de Ciencias, Universidad de Chile, Santiago 6850240 Chile"}]},{"given":"Carlos","family":"Gonzalez","sequence":"additional","affiliation":[{"name":"Centro de Estudios Cient\u00edficos, Valdivia"}]},{"given":"Ramon","family":"Latorre","sequence":"additional","affiliation":[{"name":"Centro de Estudios Cient\u00edficos, Valdivia"},{"name":"Departamento de Biolog\u00eda, Facultad de Ciencias, Universidad de Chile, Santiago 6850240 Chile"}]}],"member":"24","reference":[{"key":"R1","unstructured":"Alvarez O, Gonzalez C, and Latorre R. 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New York: Plenum, 1995, p. 53\u201391."},{"key":"R8","doi-asserted-by":"publisher","DOI":"10.1016\/0076-6879(92)07009-D"},{"key":"R9","doi-asserted-by":"publisher","DOI":"10.1016\/S0006-3495(88)83013-3"},{"key":"R10","doi-asserted-by":"publisher","DOI":"10.1016\/S0006-3495(90)82566-2"},{"key":"R11","unstructured":"Hille B. Ion Channels of Excitable Membranes. Sunderland, MA: Sinauer Associates, 2001."},{"key":"R12","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1952.sp004764"},{"key":"R13","doi-asserted-by":"publisher","DOI":"10.1007\/BF01870671"},{"key":"R14","doi-asserted-by":"publisher","DOI":"10.1038\/35102000"},{"key":"R15","doi-asserted-by":"publisher","DOI":"10.1113\/jphysiol.1976.sp011442"},{"key":"R16","doi-asserted-by":"publisher","DOI":"10.1146\/annurev.bb.06.060177.002021"},{"key":"R17","doi-asserted-by":"publisher","DOI":"10.1085\/jgp.108.3.143"},{"key":"R18","doi-asserted-by":"crossref","unstructured":"Sackmann B and Neher E. The patch clamp technique. 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