Ligand-specific temperature-dependent shifts in EC50 values for the GABAA receptor

We introduce a system for temperature control of a commercial microfluidic superfusion device that, in combination with patch-clamp, enables rapid acquisition of dose-response data at different temperatures. We obtained dose-response curves for the GABAA receptor, a ligand-gated ion channel, for two different agonists at temperatures between 25 and 40 degrees C. For GABA, the dose-response curves shifted toward higher EC50 values as the temperature increased, whereas for beta-alanine, the EC50 values were constant. This shows that temperature is an important factor for obtaining accurate estimations of EC50 values and also that such temperature effects can be ligand-specific. Using the EC50 values, we estimated the enthalpy of dissociation between the ligand and the receptor. Furthermore, the technology introduced here is generally applicable to all patch-clamp studies where temperature control is desirable, e.g., studies of kinetics and thermodynamics, drug screening, compliant ADME/Tox testing, and in studies of temperature-gated ion channels.