Experiments were conducted to determine the currents involved in the pacemaker activity of aggregates and single cells from the embryonic chick heart. Two microelectrode voltage clamp studies of embryonic chick ventricular heart cell aggregates revealed two time-dependent current components in the pacemaker range of potentials ($-$60 to $-$120 mV). Barium (Ba, 5 mM) blocked the more negatively activated time-dependent component unmasking a component which remained inwardly directed for hyperpolarizing steps beyond the potassium equilibrium potential (E$ sb{ rm K}$). This component, which was blocked by cesium (Cs, 2 mM), is consistent with an inward current which activates upon hyperpolarization (the I, model) as proposed by DiFrancesco (1981a,b), for Purkinje fibers. / In order to minimize the problems associated with the accumulation/depletion of ions in the extracellular space during voltage clamp experiments, studies were carried out on single ventricular cells or small clusters of ventricular cells.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.59533 |
| Date | January 1990 |
| Creators | Brochu, Richard |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Master of Science (Department of Physiology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001232498, proquestno: AAIMM63667, Theses scanned by UMI/ProQuest. |
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