Table 1.
Summary of main slope conductance levels and kinetic parameters of nAChRs in wild-type (WT) and nAChR subunit knockout SCG neurons
| α5β2 +α5β2α7 KO | β2 KO | α5 KO | WT | |||||
|---|---|---|---|---|---|---|---|---|
| Genotype Receptor | α3β4 | α3β4 | α3β4α5 α3β4 | α3β4 | α3β4β2 | α3β4 | α3β4α5 α3β4 | α3β4β2 |
| Main conductance (pS) | 32.6 ± 0.8 (n= 32)1 | 32.9 ± 1.2 (n= 13)5 | 32.8 ± 0.9 (n= 7/16)9 | 13.6 ± 0.5 (n= 7/16)13 | 33.7 ± 0.9 (n= 23)15 | 32.5 ± 1.9 (n= 6/23)15 | 15.4 ± 0.8 (n= 4/23) | |
| α5β2 double-KO 32.1 ± 0.8 (n= 17)2 | 32.1 ± 2.9 (n= 5)6 | 33.5 ± 1.1 (n= 8)7 | 32.3 ± 1.3 (n= 9/16)10 | |||||
| α5β2α7 triple-KO 33.3 ± 1.5 (n= 15)3 | ||||||||
| τ open time (ms) | τ1: 0.79 ± 0.10 τ2: 8.99 ± 0.55 (n= 43) 11a | τ1: 0.65 ± 0.09 τ2: 8.75 ± 0.94 (n= 9/17) | τ1: 0.30 ± 0.09 τ2: 9.16 ± 0.85 τ3: 56.7 ± 7.2 (n= 8/17)7 | τ1: 1.17 ± 0.25 τ2: 11.2 ± 1.5 (n= 7/16)11 | τ1: 1.27 ± 0.59 τ2: 25.4 ± 3.9 (n= 7/16) | τ1: 0.89 ± 0.23 τ2: 13.4 ± 1.4 (n= 17/23) | τ1: 0.38 ± 0.07 τ2: 7.63 ± 1.32 τ3: 46.3 ± 7.2 (n= 6/23) | τ1: 0.67 ± 0.05 τ2: 19.0 ± 1.7 (n= 4/23) |
| α5β2 double-KO τ1: 0.81 ± 0.14 τ2: 9.64 ± 0.70 (n= 25)2 | τ1: 0.78 ± 0.19 τ2: 10.0 ± 0.9 (n= 9/16)12 | |||||||
| α5β2α7 triple-KO τ1: 0.77 ± 0.13 τ2: 8.10 ± 0.85 (n= 18)3 | ||||||||
| τ burst length (ms) median (25th, 75th percentile) | τ: 27.3 (18.0, 32.4) (n= 43)1,4 | τ: 27.5 (22.0, 39.6) (n= 9/17) | τ1: 25.4 (16.1, 45.5) τ2: 151.9 (104.5, 215.3) (n= 8/17)8 | τ: 32.3 (23.9, 54.3) (n= 7/16)11 | n.d.14 | τ: 38.5 (30.3, 55.3) (n= 16/23) | τ1: 27.9 (16.1, 47.6) (n= 4/23)16 τ2: 115.9 (60.1, 275.9) (n= 6/23)16 | n.d.14 |
| α5β2 double-KO τ: 29.1 (19.1, 34.0) (n= 25)2,4 | τ: 47.4 (36.6, 63.0) | |||||||
| α5β2α7 triple-KO τ: 22.6 (16.8, 31.9) (n= 18)3,4 | ||||||||
Pooled data from α5β2 double-KO and α5β2α7 triple-KO mice.
Open times in all patches could be fitted using the sum of two exponential components, although three exponential components yielded a good fit in some patches as well.
Data from α5β2 double-KO mice.
Data from α5β2α7 triple-KO mice. Burst durations in α5β2 double-KO and α5β2α7 triple-KO mice do not differ significantly (P > 0.05, Mann–Whitney test).
Median values. Burst durations calculated upon separation of bursts by critical closed times (as described in the Methods section) were not normally distributed (P < 0.0011,2, Kolmogorov–Smirnov test).
α3β4 and α3β4α5 receptors have the same conductance: eight of these patches contained channels with extra-long openings (τ3: 56.7 ± 7.2 ms). The slope conductance of these putative α3β4α5 channels was 33.5 ± 1.1 pS, not significantly different from α3β4 channels in α5β2/α5β2α7 KO neurons1 (32.6 ± 0.8 pS, n= 32; P > 0.05, Student's t test).
The open time p.d.f. was fitted best by a double-exponential function with the time constants τ1 = 0.63 ± 0.14 (27 ± 8%) and τ2 = 8.89 ± 1.40 (73 ± 8%; n= 5).
The open time p.d.f. was fitted best by a triple-exponential function in eight of the β2 KO patches. Thus, τ3 was attributed to α3β4α5 receptors.
Burst duration in which channel open times required a three-exponential fit.
Channel conductance in patches in which low-conductance channels were also present.
Channel conductance in patches in which low-conductance channels were not present.
Kinetics in patches in which low-conductance channels were present. Burst durations do not significantly differ from bursts in α5β2/α5β2α7 KO neurons (P > 0.05, Mann–Whitney test).
Kinetics in patches in which low-conductance channels were not present. Burst durations differ significantly from bursts in α5β2/α5β2α7 KO neurons (P < 0.05, Mann–Whitney test).
Significantly different from conductance in α5β2/α5β2α7 KO (P > 0.0001, Student's t test).
Not determined due to the rarity of bursts.
All 23 patches taken from WT animals showed channel activity with a mean conductance of 33.7 pS. In six of these patches, the channels had extra-long openings and extended bursts with a mean conductance of 32.5 pS. Four patches contained channels with markedly reduced conductance and longer openings.
Two of the patches required fit to a single-exponential function.
1,5,9,15 Conductances do not differ significantly among the genotypes (P > 0.05, one-way ANOVA).
n= number of patches with the indicated channel activity. Unless indicated otherwise, data are mean values ± SEM.