The long term goal of our research is to define the role played in anesthesia by various forms of GABA-mediated inhibition. There is great controversy at present regarding anesthetic-enhanced GABA inhibition for various anesthetic end-points. Good evidence points to considerable involvement, for several end-points, including loss of recall, loss of consciousness and even immobility, but other experiments have suggested little or no involvement. Nor is it clear whether GABA inhibition mediated by synaptic receptors or extrasynaptic tonic receptors play the more important role in depressing circuit level signaling. Our recent discovery of important effects on GABAB, in addition to well documented effects on GABAA systems, have added to the confusion about relevant effects for a growing array of new anesthetic target sites (e.g TREK and TASK potassium channels, calcium channels, other transmitter receptors, presynaptic SNARE proteins, and sodium channels). We will focus this study on GABAA and GABAB mediated inhibition, because these appear to contribute most to depression (over 60% when combined) from our preliminary studies, but our new circuit level analysis has already provided evidence for other key sites of action as well.
Three specific aims will be addressed: 1 - to assess the role that fast and slow synaptic as well as tonic GABAA inhibition plays in CA1 circuit integration, 2 - to assess the roles these forms of inhibition play for anesthetic- induced circuit depression, and 3 - to assess the role GABAB mediated inhibition plays for anesthetics. Information from these aims is essential for designing safer and more effective anesthetics that selectively target the most relevant GABA receptors. In the immediate-term, we will contribute quantitative assessments to resolve current controversies, and assess new GABAB contributions for three classes of general anesthetics. Our results will provide the best quantitative data available upon which to model anesthetic effects using computational approaches - current models use estimates of the involvement of GABA systems that range from ~ 20 to 90 %, and there is little evidence upon which to base these estimates. As the GABA receptor subtypes underlying various forms of inhibition become known, our results will help link desired and unwanted anesthetic effects to these molecular targets.
General anesthetics are essential in modern medicine, especially for surgery, but these drugs remain among the most dangerous and poorly understood among clinically used drugs. Our research will address fundamental mechanisms of action for three important classes of anesthetics, including the intravenous agent propofol, the barbiturate pentobarbital, and volatile anesthetic isoflurane - to provide a scientific basis for safer drug design.
| MacIver, M Bruce (2014) Anesthetic agent-specific effects on synaptic inhibition. Anesth Analg 119:558-69 |
