The long-term objective of this research project is to develop – for the first time – competitive antagonists (i.e. reversal agents) for general anesthetics. This would allow clinicians to reverse anesthesia on demand and assist scientists advance their research programs. Currently, a critical obstacle to developing such antagonists for anesthetics that act via the GABAA receptor is that there are no strategies for designing competitive ligands that can bind to the receptor’s anesthetic binding sites without enhancing the receptor’s function and thus producing anesthesia. The specific goal of this research proposal is to overcome that obstacle by discovering the fundamental principles and establishing the drug design strategies that are necessary to develop anesthetic competitive antagonists for clinical and research use. We have discovered that by modifying a key region of its molecular structure, the highly efficacious anesthetic etomidate can be transformed into an anesthetic-selective competitive antagonist at the GABAA receptor that accelerates in vivo anesthetic recovery. This discovery provides important clues regarding the changes that occur in the GABAA receptor’s anesthetic binding sites as it isomerizes from closed to open, and suggests a novel strategy for designing anesthetic reversal agents using existing anesthetics as molecular templates. Aim 1 is to better understand why such modifications dramatically reduce etomidate’s binding selectivity for the open state of the GABAA receptor, almost completely abolish its intrinsic efficacy for receptor activation, and transform it into an anesthetic-specific competitive antagonist at the receptor. It will also test whether analogues containing this modification antagonize the receptor actions of other anesthetics besides propofol and etomidate. Aim 2 is to quantify the binding selectivity of these etomidate analogues for the two different classes of anesthetic binding sites located between different receptor subunits using photoaffinity labeling techniques. Aim 3 is to define the behavioral actions of these analogues in rats and test whether one with very low efficacy can accelerate recovery from hypnosis produced by different anesthetics. Currently, recovery from an anesthetic's actions must occur as a passive process whose time course is dictated by the rate of anesthetic drug clearance rather than the actual clinical need. The availability of general anesthetic competitive antagonists would have an enormous impact on patient care by allowing anesthetic emergence to be actively managed and precisely controlled. It would improve patient safety and challenge current practice models of anesthesia care by allowing potentially deadly side effects such as respiratory depression to be reversed immediately and on-demand. It would also advance scientific research by helping investigators to locate novel sites of anesthetic action, test for the possibl...