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Caffeine-induced [Ca²⁺] oscillations in neurones of frog sympathetic ganglia

Zoltán Cseresnyés, Alexander I. Bustamante and Martin F. Schneider

Single cell fluorimetry was used to monitor caffeine-induced oscillations of cytosolic [Ca²⁺] in frog sympathetic ganglion neurones in 2·0 mM K⁺ Ringer solution.

[Ca²⁺] oscillations decreased in frequency and exhibited three different amplitude patterns after the first large peak of [Ca²⁺]: (a) a series of big oscillations (BOs) of constant large amplitude (300-400 nM), (b) a series of much smaller oscillations (SOs) (40-60 nM), or (c) a series of decaying oscillations (DOs) of rapidly decreasing amplitude.

A model in which the oscillation amplitude was determined by the Ca²⁺ content of the endoplasmic reticulum (ER) whereas the oscillation frequency was controlled by how rapidly the cytosolic [Ca²⁺] reached the threshold for Ca²⁺-induced Ca²⁺ release (CICR) was able to simulate each observed pattern by varying the level of activity of the ER Ca²⁺ pump (SERCA), CICR and release-activated Ca²⁺ transport (RACT). A cumulative, cytosolic Ca²⁺-dependent inactivation of the plasma membrane (PM) Ca²⁺ influx or of the Ca²⁺-sensitive leak coefficient of the ryanodine receptors caused the oscillation frequency to decrease in the model.

Transitions between BOs and SOs and changes in [Ca²⁺] oscillations caused by ryanodine, thapsigargin, lanthanum and FCCP could also be simulated.

We conclude that RACT, SERCA, CICR and Ca²⁺-dependent PM Ca²⁺ influx are major mechanisms underlying [Ca²⁺] oscillations in these neurones.

This article has been cited by other articles:

				A. Verkhratsky Physiology and Pathophysiology of the Calcium Store in the Endoplasmic Reticulum of Neurons Physiol Rev, January 1, 2005; 85(1): 201 - 279. [Abstract] [Full Text] [PDF]

				S. I. McDonough, Z. Cseresnyes, and M. F. Schneider Origin Sites of Calcium Release and Calcium Oscillations in Frog Sympathetic Neurons J. Neurosci., December 15, 2000; 20(24): 9059 - 9070. [Abstract] [Full Text] [PDF]