Effects of low doses of caffeine on [Ca2+]i in voltage-clamped snail (Helix aspersa) neurones

The Journal of Physiology
R K Orkand, R Thomas

Abstract

1. We have measured cytosolic free Ca2+ concentrations ([Ca2+]i) in voltage-clamped snail neurones using fura-2. Transient increases in [Ca2+]i were induced by depolarizing voltage steps of 20-60 mV for 0.1-10 s from a holding potential of -50 or -60 mV. 2. Low doses of caffeine, 0.2-1 mM, increased the size of the [Ca2+]i transients by both increasing the peak and producing an undershoot. 3. Ryanodine, an inhibitor of Ca2+ release from the intracellular Ca2+ stores, and cyclopiazonic acid (CPA), an inhibitor of the Ca(2+)-ATPase of the intracellular Ca2+ stores, both reduced the size of the [Ca2+]i transients and blocked the effects of caffeine on the transients. 4. The effects of caffeine and CPA were greater on transients produced by long, small, rather than short, large depolarizations. This suggests that calcium-induced calcium release (CICR) played a greater role in the [Ca2+]i increase resulting from longer, smaller depolarizations. 5. Increasing the extracellular pH from 7.5 to over 9, which inhibits the plasmalemmal Ca(2+)-H(+)-ATPase, increased the resting [Ca2+]i level. Depolarization-induced [Ca2+]i transients became much larger while the two effects of caffeine remained. CPA was ineffective at high pH. 6. In some e...Continue Reading

Citations

Jan 25, 2003·Cell Calcium·A Verkhratsky
Sep 25, 1999·The Journal of General Physiology·S Gera, L Byerly
Feb 15, 2008·Zoological Science·Pei-Shan LiuYutaka Kirino
Oct 12, 2000·Journal of Cellular Physiology·H Y KangW H Kang
Jun 19, 2002·American Journal of Physiology. Regulatory, Integrative and Comparative Physiology·Fang-Li ZhaoScott Herness
Dec 13, 2003·Cell Calcium·Andreas BeckJoachim W Deitmer

❮ Previous
Next ❯

Related Concepts

Related Feeds

ATP Synthases

ATP synthases are enzymes located in the inner mitochondrial membrane that catalyze the synthesis of ATP during cellular respiration. Discover the latest research on ATP synthases here.