Estimated single-channel conductance of mechanically-activated channels ina spider mechanoreceptor

Noise analysis was used to estimate the single-channel conductance and numb er of channels responsible for the mechanically-activated current in the se nsory neurons of a spider mechanoreceptor organ. External slits of the VS-3 slit-sense organ in the patellar cuticle of Cupiennius salei were moved wi th a piezoelectric stimulator while glass microelectrodes penetrated the ad jacent cell bodies. Receptor currents were measured by the switching single -electrode voltage clamp technique during both step and ramp displacements of the slits. Current records were segmented in time, and the variance and amplitude of the current were obtained from each segment, to allow fitting of the variance vs, amplitude relationship by a standard equation based on a two-state channel. Mean values of 7.5 pS and 253 were obtained for the co nductance and number of channels from 75 separate recordings. These values are in good agreement with the small number of other estimates of these par ameters from different mechanoreceptor preparations. (C) 1999 Elsevier Scie nce B.V. All rights reserved.