DZP directly activates GABAA receptors. (a) The current
in response 1 mM GABA and 1 mM DZP in an oocyte expressing high
levels of GABAA receptors are shown. With this high level of
expression, we were unable to measure the maximum GABAactivated
current. The dashed line is in response to 500 mM
picrotoxin and indicates the population of spontaneously opening
wild-type abg receptors predicted by Scheme 1 (Chang & Weiss,
1999). Similar results were obtained in 16 experiments. (b) DMCM
(1 mM) reduced the baseline current consistent with a decrease in
spontaneous opening. The notch on the falling phase of the current
trace represents a modest activation that also occurs with this
concentration of DMCM. Note the slow return toward baseline
after DMCM removal, suggesting a high affinity for DMCM.
(c) The traces at the bottom show the negative vehicle controls for
DZP (PEG-300) and DMCM (ethanol). These dilutions would
correspond to concentrations of 1 mM for DZP and DMCM.