Automated fast perfusion of Xenopus oocytes for drug screening

Fast ('concentration jump') applications of neurotransmitters are crucial for screening studies on ligandgated ion channels. In this paper, we describe a method for automated fast perfusion of neurotransmitters (or drugs) during two-microelectrode voltage-clamp experiments on Xenopus oocytes. The oocytes are placed in a small bath chamber that is covered by a glass plate with two channels for the microelectrodes that are surrounded by a quartz funnel serving as a reservoir for test solutions. The oocytes are perfused in a vertical direction via the two channels in the plate. Automation of compound delivery is accomplished by means of a programmable pipetting workstation. A mean rise time for 10-90% current increase through muscle-type nACh channels of 55.0 +/- 1.3 ins (30 mu M acetylcholine) was estimated. Automation, fast perfusion rates, and economical use of compounds (approximate to 100 mu l/data point) make the system suitable for screening studies on ligand- and voltage-gated ion channels.