Spontaneous transient outward currents in smooth muscle cells

¹Department of Pharmacology and Clinical Pharmacology, St George's Hospital Medical School, London, UK. t.bolton@sghms.ac.uk

|August 1, 1996

Summary

Spontaneous transient outward currents (STOCs) in smooth muscle cells are linked to calcium releases from the sarcoplasmic reticulum. These currents may involve calcium sparks or larger events, and their generation is modulated by various calcium-regulating agents.

Area of Science:

Physiology
Cell Biology
Ion Channel Function

Background:

Spontaneous transient outward currents (STOCs) are observed in single smooth muscle cells.
STOCs are attributed to the opening of numerous calcium-activated potassium (BK) channels.
Recent findings suggest STOCs originate from spontaneous calcium releases from the sarcoplasmic reticulum (SR).

Purpose of the Study:

To investigate the relationship between SR calcium releases and STOCs in smooth muscle cells.
To explore the mechanisms underlying STOC generation, including calcium sparks and macrosparks.
To understand the role of calcium store depletion and modulation on STOC activity.

Main Methods:

Electrophysiological recordings of STOCs in smooth muscle cells.
Confocal microscopy to visualize calcium dynamics (sparks).
Pharmacological manipulation of SR calcium stores (caffeine, ryanodine, IP3, CPA, thapsigargin).

Main Results:

STOCs are associated with spontaneous SR calcium releases, potentially occurring in junctional spaces.
Some STOCs may result from larger calcium release events ('macrosparks').
Depletion of SR calcium stores abolishes STOCs, while low concentrations of certain agents can alter STOC frequency and size.

Conclusions:

STOCs in smooth muscle cells are critically dependent on SR calcium release.
The generation of STOCs involves calcium sparks and potentially macrosparks.
Modulation of SR calcium handling affects STOCs, highlighting the interplay between calcium stores and BK channel activity.

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Spontaneous transient outward currents in smooth muscle cells

Area of Science:

Background:

Purpose of the Study:

Main Methods:

Main Results:

Conclusions:

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