Small-volume and rapid extracellular solution exchange around Xenopus oocytes during voltage-clamp recordings.

A novel method for micro extracellular perfusion of Xenopus oocytes has been designed in order to minimise the amount of test solution required for drug applications during two-microelectrode voltage-clamp experiments. Voltage-clamp experiments on oocytes are performed in a glass-covered microbath without continuous perfusion. The microelectrodes access the oocytes via two small openings in the glass cover. Test solutions are applied to a funnel at the chamber inflow and the chamber volume is subsequently exchanged by operating a suction pump connected to the chamber outflow. Only 50 microl of drug- or neurotransmitter-containing solution is required for bath application. In addition, the new "funnel application technique" enables quick and timed applications of drugs or neurotransmitters to Xenopus oocytes within 200-400 ms.