Since the development of the internal perfusion technique (Akaike et al., 1978; Hamill et al., 1981), the opportunity to analyze, in the voltage clamp mode, the kinetics of voltage-gated Na⁺, K⁺, and Ca²⁺ channels of single cells, such as neurons, heart muscle cells, and smooth muscle cells, has been seized in a number of laboratories with striking success. Kinetic studies of the interaction between neurotrans-mitters and the individual receptors are also indispensable for elucidating the underlying molecular mechanisms. Several complementary approaches have been used. The first approach involves nerve stimulation and relies on the rapid removal of transmitters from the synaptic cleft by diffusion and inactivation processes (Magleby and Stevens, 1972; Kuba and Nishi, 1979; Segal and Barker, 1984). The second method uses a ligand, bis-Q, that has two conformations (cis and trans) with different affinities to the acetylcholine receptor. Rapid changes to the active trans isomer can be made by brief light flashes of appropriate wavelengths (Lester and Chang, 1977; Weinstock, 1983). However, these two methods have the same disadvantage: The time course of the concentration transient is uncertain, and the study is limited to the case of simpler systems, such as the neuromuscular junction and the single ligand trans- bis-Q. A third method has been used for making