Table 2.

Characteristics of [3H]muscimol binding to wild-type and cysteine-substituted GABAA receptors

ReceptorKD(nm)KMUT/KWTn
αβ 62 ± 51.022
αY59Cβ177 ± 212.92
αT60Cβ142 ± 302.35
αI61Cβ129 ± 82.13
αD62CβL.B.3
αV63Cβ 89 ± 151.45
αF64CβL.B.3
αF65CβL.B.5
αR66CβL.B.3
αQ67CβNo significant binding3
αS68Cβ 65 ± 81.13
αW69CβNo significant binding3
  • The affinity of muscimol binding to wild-type and mutant receptors was determined by [3H]muscimol saturation and competition binding assays as described in Materials and Methods. The means and SEM are shown for n independent experiments, each with triplicate determinations. Cysteine substitution of α1 Y59, T60, I61, V63, or S68 had little effect on muscimol affinity. L.B., Low levels of specific binding made it difficult to accurately determine the affinity of muscimol binding to these mutant receptors.