Biophysical Journal 35: 249-255 (1981)
© 1981 the Biophysical Society

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Material from the Internal Surface of Squid Axon Exhibits Excess Noise

Implications in Modeling Membrane Noise

ABSTRACT

A fluid material from a squid (Loligo pealei) axon was isolated by mechanical application of two types of microcapillary (1-3-µm Diam) to the internal surface of intact and cut-axon preparations. Current noise in the isolated material exceeded thermal levels and power spectra were 1/f in form in the frequency range 1.25-500 Hz with voltage-dependent intensities that were unrelated to specific ion channels. Whether conduction in this material is a significant source of excess noise during axon conduction remains to be determined. Nevertheless, a source of excess noise external to or within an ion channel may not be properly represented solely as an additive term to the spectrum of ion channel noise; a deconvolution of these spectral components may be required for modeling purposes.