Voltage-gated calcium channels are ubiquitously expressed in neurons and are of vital importance to proper cellular functioning. Calcium entry into cells via activation of voltage-gated calcium channels controls a wide variety of cellular functions including neurotransmitter release, muscle excitation-contraction coupling, gene regulation and activation of signaling cascades. Regulation of calcium channels via activation of G protein-coupled receptors is a prominent mechanism of calcium current inhibition and neurotransmitter release. An intriguing characteristic of this modulatory pathway is its voltage dependence whereby the degree of calcium current inhibition varies depending on the membrane voltage of the cell, and is susceptible to activity-dependent relief by trains of action potentials. Previously, it has been suggested that in chick ciliary ganglion neurons, somatostatin inhibits calcium current in a voltage dependent manner. Interestingly, the specific characteristics of the inhibition varied depending on the recording configuration used to collect data. Thus, I measured the voltage-dependence of somatostatin-mediated calcium current inhibition in individual ciliary ganglion neurons using the whole-cell and perforated patch configuration of voltage clamp recordings. The results indicate that the cytoplasmic dialysis that occurs during whole-cell recordings enhances the voltage dependence of calcium current inhibition and suggests that there is a greater concentration of activated G protein subunits in this configuration. While much is known about step depolarization-evoked calcium current and the kinetic changes that accompany G protein-mediated inhibition, relatively little is known about the effects of kinetic slowing on AP-evoked calcium current. Therefore, I used a modification of action potential waveforms was used to determine the effect of G protein activation on the kinetics of single action potential-evoked calcium current. The results demonstrate that kinetic slowing does not alter the time course of action potential-evoked calcium current and suggests that modulated channels may not contribute to AP-evoked calcium current.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-04212005-121742 |
| Date | 03 June 2005 |
| Creators | Artim, Debra Elaine |
| Contributors | Stephen D. Meriney, David Wood, Jon Johnson, Guoqiang Bi, Alison Barth, Stephen Jones |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-04212005-121742/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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