Disregulation of Potassium Channels in Menopausal Hot Flashes

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DESCRIPTION (provided by applicant): The hot flash, an abrupt sensation of heat, is the most common medical complaint among peri- and post-menopausal women. Peripherally, hot flashes are characterized by vasodilation, increased heart rate, and perspiration. The expression of the hot flash is correlated with lowered levels of circulating estrogen at the onset of menopause or surgical removal of the ovaries. Estrogen receptors are widely distributed throughout the central nervous system and the cardiovascular system. Within the central nervous system estrogen receptors are prominently expressed in the preoptic area (POA) of the hypothalamus - the location of temperature sensitive neurons associated with thermoregulation. It is thought that hot flashes are caused by a disturbance of normal thermoregulation brought on by the loss of estrogen; however, the underlying molecular, cellular, and physiological mechanism is unknown. Recently, a new family of ion channels, the background leak potassium channels or two-pore domain potassium (K2P) channels has been identified through the use of bioinformatics. In cell and tissue culture systems these channels have been shown to contribute the establishment of the resting membrane potential of cells. Activation of K2P channels causes hyperpolarization of cells resulting in inhibition of firing. Although some of the channels have been associated with temperature sensitivity, sensitivity to pain, response to inhalant anesthetics, and neuroprotection, the physiological functions of most of these channels in living organisms have yet to be established. It is hypothesized herein that estrogen regulates the expression of K2P channels in the central nervous system and that the withdrawal of estrogen results in a decrease in the number or activity of these channels. This reduction would depolarize neurons leading to greater excitability and the induction of hot flashes. The work proposed in this application will use a functional bioassay, radiotelemetric monitoring of tail skin temperature from estrogen deficient and replete mice, to monitor the effects of drugs that activate and inhibit K2P channels in a whole animal model. Immunohistochemistry will be used to determine whether or not the proteins are expressed in the same cells as estrogen receptors. Expression of the messenger RNAs for the channels will be quantified using real time-PCR and in situ hybridization. Although this application will investigate the role of K2P channels in generating hot flashes, increasing our understanding of the physiological functions of these channels may provide insight into mechanisms of other age-associated diseases associated with hyperexcitability of the central nervous system. Hot flashes are the most common medical complaint among peri- and post-menopausal women. Currently, the most commonly used treatment to alleviate hot flash symptoms is hormone replacement therapy (HRT). Unfortunately, HRT is associated with several risks, including an increase in hormone dependent cancers, leading many to seek other treatments. The cellular and molecular mechanisms that cause hot flashes are unknown. The work proposed in this application is designed to investigate the underlying cellular and molecular mechanisms responsible for hot flashes, leading to the development of safe and effective treatments.