PNSCROLL, a software package for graphical interactive analysis of single channel patch clamp currents and other binary file records: Under mouse control

The Journal of General Physiology

1991

A B S T R A C T The transient potassium current, IK(t), of enzymatically dissociated rat olfactory receptor neurons was studied using patch-clamp techniques. Upon depolarization from negative holding potentials, IK(t) activated rapidly and then inactivated with a time course described by the sum of two exponential components with time constants of 22.4 and 143 ms. Single-channel analysis revealed a further small component with a time constant of several seconds. Steady-state inactivation was complete at -20 mV and completely removed at -80 mV (midpoint -45 mV). Activation was significant at -40 mV and appeared to reach a maximum conductance at +40 mV (midpoint -13 mV). Deactivation was described by the sum of two voltage-dependent exponential components. Recovery from inactivation was extraordinarily slow (50 s at -100 mV) and the underlying processes appeared complex. IK(t) was reduced by 4-aminopyridine and tetraethylammonium applied externally. Increasing the external K + concentration ([K+]o) from 5 to 25 mM partially removed Ix(t ) inactivation, usually without affecting activation kinetics. The elevated [K+]o also hyperpolarized the steady-state inactivation curve by 9 mV and significantly depolarized the voltage dependence of activation. Single transient K + channels, with conductances of 17 and 26 pS, were observed in excised patches and often appeared to be localized into large clusters. These channels were similar to Ix(t) in their kinetic, pharmacological, and voltage-dependent properties and their inactivation was also subject to modulation by [K+]o . The properties of Ix(t) imply a role in action potential repolarization and suggest it may also be important in modulating spike parameters during neuronal burst firing. A simple method is also presented to correct for errors in the measurement of whole-cell resistance (Ro) that can result when patch-clamping very small cells. The analysis revealed a mean corrected R o of 26 GI-/for these cells.

Section: Data Analysis and Displaymentioning

confidence: 99%

Properties of transient K+ currents and underlying single K+ channels in rat olfactory receptor neurons.

The Journal of General Physiology

1991

“…All experiments were performed at room temperature (20-22'C). Recordings were later filtered at 1 kHz, digitized at 2.5 kHz, and analyzed using the software package PNSCROLL (Barry and Quartararo, 1990). Data are expressed as mean ± SEM.…”

Section: Methodsmentioning

confidence: 99%

Odorant-induced currents in intact patches from rat olfactory receptor neurons: theory and experiment

Chiu

1997

Biophysical Journal

Odorant-induced currents in mammalian olfactory receptor neurons have proved difficult to obtain reliably using conventional whole-cell recording. By using a mathematical model of the electrical circuit of the patch and rest-of-cell, we demonstrate how cell-attached patch measurements can be used to quantitatively analyze responses to odorants or a high (100 mM) K+ solution. High K+ induced an immediate current flux from cell to pipette, which was modeled as a depolarization of approximately 52 mV, close to that expected from the Nernst equation (56 mV), and no change in the patch conductance. By contrast, a cocktail of cAMP-stimulating odorants induced a current flux from pipette into cell following a significant (4-10 s) delay. This was modeled as an average patch conductance increase of 36 pS and a depolarization of 13 mV. Odorant-induced single channels had a conductance of 16 pS. In cells bathed with no Mg2+ and 0.25 mM Ca2+, odorants induced a current flow from cell to pipette, which was modeled as a patch conductance increase of approximately 115 pS and depolarization of approximately 32 mV. All these results are consistent with cAMP-gated cation channels dominating the odorant response. This approach, which provides useful estimates of odorant-induced voltage and conductance changes, is applicable to similar measurements in any small cells.

“…For analysis and display, all data were filtered at 1 kHz and digitized at 2.5 kHz. Analysis was done on an IBM-AT computer using pnscroll software (Barry & Quartararo 1990) and least-square regressions were made using SigmaPlot (Jandel, Corte Madera, California). For single-channel data displayed in figures 3-5, nonlinear baselines induced by voltage steps were compensated by digitally subtracting several averaged traces to the channel reversal potential and scaled if necessary.…”

Section: E T H O D Smentioning

confidence: 99%

Slowly activating K ⁺ channels in rat olfactory receptor neurons

1991

Proc. R. Soc. Lond. B

Patch-clamp techniques were used to investigate slowly activating, Ca(2+)-insensitive K+ channels of isolated rat olfactory receptor neurons. These channels had a unitary conductance of 135 pS and were only found in a small proportion (less than 5%) of membrane patches. Upon depolarization to voltages more positive than -50 mV, the channels activated gradually over a period of at least 10 s. When hyperpolarized to negative voltages, channel activity deactivated in a slow but voltage-dependent manner. These channels may underlie a slowly activating K+ current that is observed in approximately 30% of whole-cell recordings. Similar single channels have been reported in smooth muscle cells, but this is the first demonstration of these channels in any type of neuron. The channels may contribute to the spike frequency adaptation and post-stimulus hyperpolarization that are observed during the excitatory response to odorants. They may also contribute to cell repolarization following large odorant-stimulated receptor currents.