Biology and Biomedical Sciences: Neurosciences
Date of Award
Doctor of Philosophy (PhD)
Chair and Committee
Lawrence B Salkoff
Sodium-activated potassium channels: KNa channels) are a small family of high-conductance K+ -channels activated by increases in the intracellular sodium concentration. KNa channels are broadly expressed in the nervous system, but the role, and even existence, of KNa channels has been overlooked or doubted by neurophysiologists for many years. In the face of evidence to suggest a role for KNa channels in normal physiology, resting Na+ concentrations are lower than reported to be sufficient for activation of KNa channels. This contradiction coupled with methodological shortcomings of some investigations into KNa channels tempered acceptance of a contribution of KNa channels in normal conditions. The goal of my dissertation research has been to determine if KNa channels are participants in the normal physiology of neurons.
I have demonstrated the prominent activation of KNa channels by sodium influx under normal physiological conditions in neurons of the rat central nervous system. Large KNa currents were revealed by preventing sodium influx using multiple experimental manipulations in neurons prepared from multiple brain regions. Transfection of neurons with siRNA directed against Slack was used to demonstrate its contribution to the encoding of KNa channels.
Many of my experiments emphasize the importance of the persistent sodium current: INaP) as a source of sodium to activate KNa channels. One line of these experiments entailed the recording and measurement of the activity of individual KNa channel in membranes isolated from neurons. This work is the first demonstration of KNa channel activation by sodium-influx using single channel recordings. I also present results demonstrating that INaP is active across a broad range of voltages, including membrane resting potentials, using both whole cell recordings as well as recordings of individual sodium-channels from isolated patches.
Finally, I've demonstrated that after blocking sodium influx, the resulting decrease in KNa channel activity is a slow process: τ ~ 13 seconds). I developed a strategy to isolate KNa channel activity in neurons by taking advantage of this slow decrease in KNa channel activity. Isolation of neuronal KNa currents has not previously been possible due to a lack of specific antagonists for KNa channels.
Hage, Travis Allen, "Activation of sodium-activated potassium channels by sodium-influx" (2012). All Theses and Dissertations (ETDs). 957.