This study is to investigate interactions of general anesthetics with neuronal membrane constituents to explore regions of the membrane that are responsible for general anesthesia. Nuclear magnetic resonance (NMR) spectroscopy will be used to characterize possible binding sites for general anesthetics, particularly xenon and fluorinated drugs, in model membranes, brain tissue homogenates, and perfused rat brain slices. Dynamic polarization transfer, cross-relaxation (nuclear Overhauser effect), and multiple-quantum coherence transfer techniques will be used interchangeably, with an emphasis on correlating and integrating the results from these simplified systems with the physiological states of general anesthesia. The long-term goal is to identify the mechanisms of general anesthesia and further to shed light on theories of consciousness, sleep, and memory. Our general approach includes the following four steps: Step 1: to determine if specific interactions exist between general anesthetics and membrane constituents; Step 2: to identify the site or sites where such interactions occur and to determine the specificity of such interactions; Step 3: to determine which interaction site or sites are the site(s) of anesthetic action and which are not; Step 4: to investigate why the interactions at the site(s) of action produce general anesthesia.
The specific aims of this study are: 1. To test the hypothesis that the general anesthetic state is brought about by anesthetic binding to a group of preferred sites in the neuronal membrane. 2. To identify these sites by using NMR cross-relaxation and selective polarization transfer between nuclei in anesthetics (e.g. 129Xe) and in membranes (e.g. 1H). 3. To determine the relevance of each interaction site to general anesthesia by administering xenon simultaneously with one or more potent anesthetics or nonanesthetics of similar chemical structure to potent anesthetics and then analyzing the effects of these second drugs on xenon binding in the membrane; 4. To verify that the additivity of general anesthetic potencies, such as MAC (minimum alveolar concentration), is indeed valid at the sites of true anesthetic action.
| Liu, Lu Tian; Haddadian, Esmael J; Willenbring, Dan et al. (2010) Higher susceptibility to halothane modulation in open- than in closed-channel alpha4beta2 nAChR revealed by molecular dynamics simulations. J Phys Chem B 114:626-32 |
