Ligand gated ion channels often display receptor desensitization, meaning that the receptor mediated response diminishes in the presence of compound. Receptor desensitization makes ion channels more challenging compared to voltage gated ion channels. Factors like exposure time and intervals between exposures affect how deeply the ion channels have desensitized and to what extent the receptor population has recovered from desensitization.
A method was developed for the Patchliner to minimize as well as control ligand exposure time and the intervals between the ligand exposures. Here, the pipette arm of the Patchliner was used to aspirate first a plug of buffer, followed by a smaller plug of compound. When added to the cell, the cell would first experience the compound and then the following wash. When investigating modulators of the agonist response, for instance antagonists, a pre-incubation step can be included as well as removing the agonist in the presence of the antagonist, by using antagonist-containing solution for the wash step.

The recordings shown were made from the same cell, exposing GABAA receptor expressing HEK-cells to different concentrations of GABA (1, 3, 10 µM). In the first set, the cell was exposed to GABA for 20 s followed by 40 s wash. This way, the cell was exposed to a new dose of GABA every 60 s. In the two following sets, GABA and wash buffer were subsequently aspirated by the pipette arm of the Patchliner. When applied to the cell, it is first exposed to GABA and then to wash buffer. The exposure time to GABA was 1 s and the cell was exposed to a new GABA concentration every 30 s.

The antagonist bicucuilline was investigated using the stack application approach. First, as a control, three applications of GABA, 3µM, was made to the cell, to check for the stability of the of the peak current amplitudes. Further on, the cells were pre-incubated with 10 µM bicuculline before co-application of bicuculline, 10 µM, and GABA, 3 µM. The wash solution in the stack was bicuculline, 10 µM, alone. A control set of 3 GABA exposures followed the antagonist application. The experiment was repeated 3 times, resulting in more than 90 additions to the cell, and an experiment lasting for 50 minutes