Figure 2.

Channel desensitization and direction of current flow do not affect fluorescence changes (ΔF) at the α1L127C site. (A) The oocyte expressing α1L127Cβ2γ2L receptors labelled with Alexa Fluor 546 C5 maleimide was exposed to a 60 s pulse of 1 mM GABA. The current response shows a considerable degree of desensitization during drug application. Channel desensitization was not accompanied by changes in ΔF. The oocyte was clamped at −60 mV. (B) The oocyte was clamped at −15 mV (top) or −60 mV (bottom), resulting in outward or inward current flow respectively. Regardless of the direction of current flow, channel activation was accompanied by an increase in ΔF indicating that the fluorophore is exposed to a less polar environment. The dashed line in the fluorescence recording at −60 mV shows the mean level of ΔF at −15 mV (from top panel).