Abstract
The tight-seal whole cell recording technique with patch pipettes was used to study membrane currents of smooth muscle cells freshly dissociated from the esophagus of cats. Under voltage clamp with K+ in the pipette, depolarizing commands elicited an initial inward current followed by a transient outward current that peaked and then declined to reveal spontaneous outward currents (SOCs). SOCs were evident at -60 mV and more positive potentials. The reversal of SOCs at the K+ equilibrium potential and their suppression by tetraethylammonium chloride lead to the conclusion that they represent the activity of K+ channels. Acetylcholine (ACh) caused reversible contraction of these cells and had two successive effects on membrane currents, causing transient activation of K+ current followed by suppression of SOCs. Both of these effects were blocked by atropine. Consistent with these observations, in current clamp, ACh caused a transient hyperpolarization followed by depolarization. The inward current activated by depolarization was blocked by external Cd2+, consistent with the inward current being a voltage-activated calcium current. Two types of Ca2+ current could be distinguished on the basis of voltage-activation range, time course of inactivation and 'run-down' during whole cell recording.
Original language | English (US) |
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Pages (from-to) | G794-G802 |
Journal | American Journal of Physiology - Gastrointestinal and Liver Physiology |
Volume | 258 |
Issue number | 5 21-5 |
DOIs | |
State | Published - 1990 |
All Science Journal Classification (ASJC) codes
- Physiology
- Hepatology
- Gastroenterology
- Physiology (medical)