Table 2

Single-channel parameters for three nAChR agonists

	Nic		GTS-21		Epi
γ (pS)	26.3±0.2	42.0±0.3	61.1±0.4	82.6±0.5	25.5±0.6	42.9±1.0	62.5±0.6	82.3±1.0	26.1±0.3	40.6±0.2	60.1±0.5	80.3±1.0
τ_B(μs)	57±5	53±3	71±7	122±12	95±36	55±10	71±11	134±14	63±9	194^2-150±14	60±9	115±49
A _B(%)	70.9±8.5	51.9±13.8	93.4±2.6	99.5±0.6	91.5±5.9	88.2±6.7^2-150	88.5±6.5	97.6±2.8	45.5±12.9	29.8±13.2	88.6±8.6	100
P _open,brief(%)	0.022±0.004	0.024±0.004	0.068±0.014	0.059±0.010	0.010±0.003^2-150	0.025±0.009	0.052±0.018	0.043±0.016	0.009±0.001^2-150	0.015±0.002^2-150	0.007±0.002^2-150	0.003±0.001^2-150
τ_i(μs)	400±59	523±123	738±208	698	632±334	370±106	624±212	545	966±203^2-150	1189±176^2-150	859±432	N.D.
A_i(%)	23.3±9.3	29.2±10.3	2.5±2.2	0.5±0.6	8.5±5.9	10.9±5.8	11.5±6.5	2.4±2.8	38.3±8.6	56.0±10.6	11.4±8.6	0.0±0.0
τ_L(μs)	3544±815	2790±658	2059±540	N.D.	N.D.	5659	N.D.	N.D.	3689±450	4025±607	N.D.	N.D.
A _L(%)	5.8±3.1	18.9±6.0	4.0±2.9	0.0±0.0	0.0±0.0	0.9±1.0^2-150	0.0±0.0	0.0±0.0	16.1±7.8	14.3±7.1	0.0±0.0	0.0±0.0
P _open,long(%)	0.052±0.010	0.399±0.098			0.011±0.004^2-150	0.015±0.006^2-150			0.121±0.032^2-150	0.862±0.154^2-150

All values are presented as mean ± S.E.M. and were obtained from single channel current records obtained at −100 mV using 0.5 μM Nic, 1 μM GTS-21, or 10 nM Epi, each applied for 40 s. Open time constants (τ) and relative histogram areas (A) for brief (B), intermediate (i) and long (L) openings in each conductance class (γ) were derived from patches in which the total number of accepted events (N_T) exceeded 1000 for Nic (N_T = 1843 ± 287, n = 5 patches), 200 for GTS-21 (N_T = 800 ± 264, n = 4), and 800 for Epi (N_T = 1264 ± 291, n = 7) as outlined in the text. Because events <98 μs were unresolved, τ_B values should be considered estimates. For all agonists, events with durations ≤200 μs were classified as brief, and those with durations >200 μs were classified as intermediate or long. The cutoff for long events was 1 ms for Nic and GTS-21 and 2 ms for Epi. P_open values shown were determined empirically from all patches with N_{T >} 200 for Nic and Epi (N_T = 749 ± 126,N_T = 26 and 707 ± 142,n = 27, respectively) and N_{T >}100 for GTS-21 (N_T = 464 ± 276,n = 8) as described under Materials and Methods. P_open,brief values were compiled from events with durations ≤200 μs, whereasP_open,long values were compiled from events with durations >200 μs (i.e., intermediate and long events). In the patches subjected to detailed kinetic analysis,P_open values obtained using the relevant τ values were indistinguishable from those obtained empirically except for the long 25-pS nAChR events induced by nicotine. In one case,P_open,long derived using τ_L(0.124) was about 2-fold larger than the empirically obtained value.

N.D., not determined.
↵2-150 Significant difference (p < 0.05) compared with those obtained with Nic.