%0 Journal Article %1 Fishman:1975p45808 %A Fishman, H M %A Poussart, D M %A Moore, L E %D 1975 %J J Membr Biol %K Animals, Axons, Chloride, Decapodiformes Electrophysiology, Membrane Potassium Potentials, Sodium, %N 3-4 %P 281--304 %T Noise measurements in squid axon membrane %V 24 %X A small area (10(-4) to 10(-5) cm2 patch) of the external surface of a squid (Loligo pealei) axon was "isolated" electrically by means of a pair of concentric glass pipettes and sucrose solution to achieve a low extraneous noise measurement of spontaneous fluctuations in membrane potential and current. The measured "small-signal" impedance function of the isolated patch in seawater was constant at low frequencies and declined monotonically at frequencies beyond 100Hz. It is shown that the power-density spectrum (PDS) of voltage noise, which generally reflects the current-noise spectrum filtered by the membrane impedance function, is equivalent to the power spectrum of current-noise up to frequencies where the impedance decline is significant (Fishman, 1973a, Proc. Nat. Acad. Sci. USA 70:876). This result is in contrast to an impedance resonance measured under uniform constant-current (internal axial wire) conditions, for which the voltage-noise PDS reflects the impedance resonance. The overdamped resonance in the patch technique is a consequence of the relatively low resistance (1 Momega) pathways through the sucrose solution in the interstitial Schwann cell space which surround and shunt the high resistance (10-100 Momega) membrane patch. Current-noise measurements during patch voltage clamp extend observation of patch ion-conductance fluctuations to 1 kHz. Various tests are presented to demonstrate the temporal and spatial adequacey of patch potential control during current-noise measurements.

@article{Fishman:1975p45808, abstract = {A small area (10(-4) to 10(-5) cm2 patch) of the external surface of a squid (Loligo pealei) axon was "isolated" electrically by means of a pair of concentric glass pipettes and sucrose solution to achieve a low extraneous noise measurement of spontaneous fluctuations in membrane potential and current. The measured "small-signal" impedance function of the isolated patch in seawater was constant at low frequencies and declined monotonically at frequencies beyond 100Hz. It is shown that the power-density spectrum (PDS) of voltage noise, which generally reflects the current-noise spectrum filtered by the membrane impedance function, is equivalent to the power spectrum of current-noise up to frequencies where the impedance decline is significant (Fishman, 1973a, Proc. Nat. Acad. Sci. USA 70:876). This result is in contrast to an impedance resonance measured under uniform constant-current (internal axial wire) conditions, for which the voltage-noise PDS reflects the impedance resonance. The overdamped resonance in the patch technique is a consequence of the relatively low resistance (1 Momega) pathways through the sucrose solution in the interstitial Schwann cell space which surround and shunt the high resistance (10-100 Momega) membrane patch. Current-noise measurements during patch voltage clamp extend observation of patch ion-conductance fluctuations to 1 kHz. Various tests are presented to demonstrate the temporal and spatial adequacey of patch potential control during current-noise measurements.}, added-at = {2009-11-12T16:21:13.000+0100}, author = {Fishman, H M and Poussart, D M and Moore, L E}, biburl = {https://www.bibsonomy.org/bibtex/2daf26d1738e37ba98462d4e38fba8753/fdiehl}, date-added = {2009-09-28 20:35:35 +0200}, date-modified = {2009-11-10 09:46:53 +0100}, description = {bib-komplett}, interhash = {e33e6e2715e95fdfd9317c928cf0ba9e}, intrahash = {daf26d1738e37ba98462d4e38fba8753}, journal = {J Membr Biol}, keywords = {Animals, Axons, Chloride, Decapodiformes Electrophysiology, Membrane Potassium Potentials, Sodium,}, language = {eng}, local-url = {file://localhost/Neurobio/Papers/1214277.pdf}, month = Dec, number = {3-4}, pages = {281--304}, pmid = {1214277}, rating = {0}, timestamp = {2009-11-12T16:21:15.000+0100}, title = {Noise measurements in squid axon membrane}, uri = {papers://7B65697B-E216-4648-8A41-C67830C0DC73/Paper/p45808}, volume = 24, year = 1975 }