The GABA-A receptor is in the brain expressed in up to 20 different subunit compositions usually two a two b and one g subunit. Some of the compositions are dominantly expressed in areas related to a certain function, like the 5 is located in hippocampus and related to memory while a1 is more diffusely spread and related to sedation. However, usually there is a mixture of receptor forms in a certain brain area and therefore a specific receptor subtype is difficult if not impossible to study in situ. Another problem is that the physiological exposure time of GABA and other compounds is in millisecond range. To overcome these problems we have developed two HEK-293 cells lines expressing either human a1b2g2 or a5b3g2 GABA-A receptor. By combining a Dynaflow^TM platform integrated with a patch-clamp equipment for measurements of chloride ion flux in single HEK- 293 cells it is possible to expose a cell only expressing one human GABA-A receptor subtype during a few milliseconds. With short (ms) exposure time problems with desensitization are not seen and the receptor-opening pattern is similar to the one at spontaneous GABA release. With this technique results in the HEK-293 cells expressing a1b2g2 GABA-A receptors show concentration response curves for GABA with an EC₅₀ value of 4 mM and E_max 2500 pA. For a5b3g2, the EC50 value is 15 mM and the maximal effect 5200 pA.