Abstract
1. Caffeine was applied locally to one region of a resting cell via an extracellular pipette while simultaneously imaging the concentrations of intracellular calcium ([Ca2+](i)) and intracellular caffeine ([caffeine](i)). 2. Local application of caffeine produced a rise of [caffeine](i) which was confined to the region of the cell near the pipette. There was also a local increase of Ca2+](i) which then, in most resting cells, propagated along the cell as a linear Ca2+ wave. The initial magnitude of the rise of [Ca2+](i) was greater than that of the electrically stimulated Ca2+ transient. 3. As the wave of increase of [Ca2+(i), propagated along the cell it decreased in both amplitude and velocity in cells that had not been treated to elevate the cellular Ca2+ load. 4. In some cells the caffeine response did not propagate significantly. In these cases an increase of the cellular Ca2+ load enabled caffeine-induced Ca2+ wave propagation along the entire cell length without significant decay in amplitude and velocity. 5. Previous work has shown that an electrically evoked local systolic Ca2+ transient does not propagate. The fact that the caffeine-evoked response does propagate and the correlation between decay of amplitude and velocity suggest that the transient has to be a certain size before it can propagate. It is suggested that one of the factors which favour propagation of waves under conditions of elevated sarcoplasmic reticulum Ca2+ content is the increased release of Ca2+.
Original language | English |
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Pages (from-to) | 319-326 |
Number of pages | 7 |
Journal | Journal of Physiology |
Volume | 489 |
Issue number | 2 |
Publication status | Published - 1 Dec 1995 |
Keywords
- Animals
- pharmacology: Caffeine
- metabolism: Calcium
- Dose-Response Relationship, Drug
- Electric Stimulation
- drug effects: Heart
- Microscopy, Confocal
- Rats
- Research Support, Non-U.S. Gov't