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Fabrication and Implantation of Miniature Dual-element Strain Gages for Measuring In Vivo Gastrointestinal Contractions in Rodents.
Published on: September 18, 2014
Electrophysiological properties of gastric pacemaker potentials
Yoshihiko Kito1, Hikaru Suzuki
1Department of Physiology, Nagoya City University Medical School, Mizuho-ku, Nagoya 467-8601, Japan.
Journal of Smooth Muscle Research = Nihon Heikatsukin Gakkai Kikanshi
|December 26, 2003
Summary
Pacemaker potentials in guinea-pig gastric antrum involve distinct mechanisms. The primary phase relies on voltage-dependent Ca2+ channels, while the plateau phase uses Ca2+-activated Cl- channels and internal Ca2+ stores.
Area of Science:
- Gastroenterology
- Cell Physiology
- Electrophysiology
Background:
- Interstitial cells of Cajal (ICC-MY) in the gastric antrum generate pacemaker potentials crucial for gut motility.
- Pacemaker potentials exhibit a biphasic waveform with distinct primary and plateau components.
Purpose of the Study:
- To elucidate the distinct ionic mechanisms underlying the primary and plateau components of pacemaker potentials in ICC-MY.
- To investigate the roles of intracellular calcium stores and mitochondrial function in generating these potentials.
Main Methods:
- Electrophysiological recordings from guinea-pig gastric antrum ICC-MY.
- Pharmacological manipulation using solutions with varying ion concentrations ([Ca2+]o, [K+]o, [Cl-]o) and specific channel inhibitors (BAPTA-AM, DIDS, cyclopiazonic acid, 2-APB, CCCP).
Main Results:
- The primary component is sensitive to extracellular calcium and membrane depolarization, suggesting voltage-dependent Ca2+ channel involvement.
- The plateau component is inhibited by low chloride and DIDS, indicating Ca2+-activated Cl- currents.
- Inhibition of Ca2+ pumps and IP3-sensitive Ca2+ stores (using cyclopiazonic acid and 2-APB) affects plateau duration and abolishes potentials, respectively.
- Mitochondrial uncoupler CCCP abolishes potentials, implicating mitochondrial Ca2+ handling.
Conclusions:
- Pacemaker potentials comprise two distinct components: a primary phase mediated by voltage-dependent Ca2+ channels and a plateau phase involving Ca2+-activated Cl- channels.
- IP3-sensitive Ca2+ stores and mitochondrial function are essential for pacemaker potential generation.
- Pacemaker potentials are initiated by unitary potentials linked to mitochondrial Ca2+ handling, followed by downstream ionic events.
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