Table 1.

Kinetic properties of GABAA receptor currents

α1β2γ2Lα1(L264T)β2γ2Lα1(S270I)β2γ2L
Fraction spontaneously active receptors1-a<0.0001  (4)0.36  ± 0.151-b (6)0.005  ± 0.00131-b (6)
EC50m)
 Internal control25  ± 0.7 (30)0.30  ± 0.0231-c (8)1.3  ± 0.101-c (15)
 Paired controls27  ± 2.9 (4)0.35  ± 0.0731-c (3)2.1  ± 0.331-c (4)
 Hill coefficient
 Internal control1.3  ± 0.050.83  ± 0.0471-c1.3  ± 0.13
 Paired controls1.1  ± 0.110.8  ± 0.121-c1.0  ± 0.15
Activation rates
 Low GABA (sec−1)8  ± 1.0 (8)4  ± 1.81-c (12)5  ± 1.41-c (7)
 High GABA (sec−1)3400  ± 1500 (30)3900  ± 1500 (8)3800  ± 2500 (21)
Fast desensitization (sec−1)20  ± 10.8 (12)20  ± 10.4 (7)
Slow desensitization (sec−1)1.0  ± 0.35<0.11-c (8)0.9  ± 0.25
Percentage fast30  ± 9.035  ± 10
Percentage slow70  ± 8.91001-c65  ± 10
Fast resensitization (sec−1)10  ± 5.0 (3)
Slow resensitization (sec−1)0.076  ± 0.00770.05  ± 0.00251-c (3)
Percentage fast30  ± 10
Percentage slow70  ± 101001-c
Fast deactivation (sec−1)50  ± 13 (7)
Slow deactivation (sec−1)7  ± 2.11.1  ± 0.401-c (7)2.9  ± 0.631-c (6)
Percentage fast60  ± 17
Percentage slow40  ± 17 1001-c1001-c
  • Values are reported as mean ± SD. The number of experiments is reported in parentheses.

  • F1-a Estimated from picrotoxin-sensitive leak currents and maximal GABA-activated currents (Fig. 2). This estimate assumes that the conductance of receptors that open in the absence of GABA is identical to that when GABA is bound.

  • F1-b Value differs from zero atp ≤ 0.05.

  • F1-c Value differs from wild-type GABAA receptors at p ≤ 0.01.