The frequency of openings and mean open time also influences mean conductance of both subpopulations.
Additional challenges for detection of whole-cell α7* nAChR-mediated responses arise from the extremely short mean open time (∼100 µs) of individual α7* nAChR ion channels [54].
Peak ensemble average current (Ipeak) in old tg CaV1.2 mice was enhanced (−56±14 fA vs. −23±7 fA, p<0.05) due to an increased fraction of active sweeps, mean open time, and mean open probability, and a decrease of mean closed time (tclosed).
The mean intraburst interval as well as total mean open time were significantly shorter in patches from VB cells (in VB: 1.84 ± 0.12 ms, n = 10 and 1.62 ± 0.11 ms, n = 10 for mean intraburst interval and mean open time, respectively, and in RT: 2.46 ± 0.12 ms, n = 5 and 2.20 ± 0.11 ms, n = 5 for mean intraburst interval and mean open time, respectively, P < 0.05, Fig. 4C).
However, from past work it is clear that derivatives produced at specific loci on the brevetoxin backbone impart a differential set of "activities" that encompass effects on activation potential, mean open time, inactivation, and persistent depolarization due to subconductance state prevalence.
It has been proposed that RyR3 may be preferentially targeted to the SR within these junctions because, compared with RyR1 and RyR2, RyR3 exhibits a relatively high EC50 for CICR, a marked Ca2+-dependent increase in gain (open probability, Po + mean open time) and a greater resistance to inactivation by high (mM) [Ca2+] (for detailed discussion see Ref. 48).
In patches with a small number of channels, the mean open times of α1β2γ2 and α3β2γ2 receptors, determined for 4 s time windows, were not significantly different (1.42 ± 0.05 ms, n = 6 and 1.57 ± 0.07 ms, n = 7).
The mean open dwell time for MscS-Ec channels is ∼150 ms (13) at low activating pressures in membrane patches, i.e., pressures required to open only one or two channels in each membrane patch tested.
Idealization of the currents was performed at a bandwith of 10 kHz using the segmentation k-means hidden Markov algorithm (Qin 2004) with a C↔O model (both rate constants = 100 s−1) or by a half-amplitude threshold-crossing algorithm after additional low-pass filtering to 3 kHz to obtain single channel open amplitude, open probability, and mean open and close times.
These rate constants were used to calculate the PDFs, mean open and mean closed times in Figure 2. We next investigated whether constitutive activity of these channels influenced the cellular membrane potential (V m).
