A system for rapid solution exchange on Xenopus laevis oocytes in the two-electrode voltage-clamp mode (Madeja et al., 1991) was improved for investigations on oocytes with removed follicular tissues. The speed of application and the time for potassium ions to reach the oocyte membrane (t50) was found to be about 40 ms in oocytes without follicular tissues and 360 ms for oocytes with follicular tissues. This rate of solution exchange is fast enough to measure the fast desensitizing component of the AMPA current response.