patch-clamp electrophysiology can detect the currents passing through ion channel proteins in verve cell membranes with single molecule resolution. The goal of this proposal is to use patch- clamp methods to study one of the signal transduction mechanisms of opiate receptors in a region of the brain thought to be involved in dependence on opiate drugs. By generating precise molecular-level data bout the mechanisms through which opiate drugs affect the electrical activity of neurons, this proposal seeks to provide information that may be useful in the interpretation of less reductionist studies, such as neuroimaging, of opiate effects on brain activity. Neurons will be acutely dissociated from a sub- region of the rat amygdala and used for patch-clamp experiments, while immunocytochemical methods will be used to identify the cells. The basic pharmacological and biophysical properties of a 130 pS conductance potassium-permeable channel of these neurons will then be examined. Preliminary studies from this laboratory have shown this channel to be activated by metenkephalin in a naloxone-sensitive manner. Subsequently, the effects of chronic morphine treatment on the opening and closing kinetics of this channel will be characterized. In so doing, it may be possible to identify mechanisms underlying tolerance to opiate drugs, whereby addicts need greater and greater amounts of drug to attain the same effect. Additional studies will examine how the noradrenergic drug clonidine affects opioid-modulated channels. Clonidine is used clinically to treat addicts withdrawing from drug abuse, and a better understanding of its mechanism of action may eventually help in the development of improved strategies for alleviating withdrawal symptoms. By studying opiate effects on single ion channels, the work proposed here seeks to provide basic knowledge about opiate receptor function with particularly high resolution and precision.
| Murphy, R; Freedman, J E (2001) Morphine and clonidine activate different K+ channels on rat amygdala neurons. Eur J Pharmacol 415:R1-3 |
| Chen, X; Marrero, H G; Freedman, J E (2001) Opioid receptor modulation of a metabolically sensitive ion channel in rat amygdala neurons. J Neurosci 21:9092-100 |
| Chen, X; Marrero, H G; Murphy, R et al. (2000) Altered gating of opiate receptor-modulated K+ channels on amygdala neurons of morphine-dependent rats. Proc Natl Acad Sci U S A 97:14692-6 |
