Multi-Dimensional Characterization of the Desensitization Behavior of Temperature- and H+-Activated Human TRPV1 Channels using Microfluidics

Abstract

This work describes the pH- and temperature-dependence of acute desensitization and tachyphylaxis in human TRPV1 channels. We use an in-house developed microfluidic device and associated methods, which independently can control the temperature and the solution environment (e.g. the pH) around patch-clamped cells, as well as the time a cell is exposed to different solutions. Thus, cells can be stimulated and controlled in a multi-dimensional parameter space. Our results show that if TRPV1 channels are exposed repeatedly to low pH applications, the rate of desensitization becomes progressively slower, whereas the rate of channel activation remains unchanged. Also, both the rate of activation and the rate of acute desensitization increase at higher temperatures. The extent of tachyphylaxis is found to be dependent on pH, temperature, and exposure time. We also show that both the desensitization rate and the extent of tachyphylaxis are correlated to current density. This could be due to the fact that Ca2+ is an important factor for both acute desensitization and tachyphylaxis, and since TRPV1 is permeable to Ca2+, the current density is proportional to Ca2+ influx.