Tetracaine has been a commonly used tool for studying the events of excitation-contraction coupling (E-CC). It not only alters intramembrane charge movement (Huang, 1981;Hui, 1983) but suppresses the calcium transients (Vergara & Caputo, 1983;Csernoch et al. 1988) by interfering with the release of calcium from the sarcoplasmic reticulum (SR; Pizarro et al. 1992). In both intact and cut fibres tetracaine preferentially eliminates the delayed, qã hump, component of intramembrane charge (e.g. , although cut fibres seem to be more sensitive (Csernoch et al. 1988) towards the drug. Most of our knowledge regarding the time course of SR calcium release (for review on calcium release see e.g. Melzer et al. 1995) in the presence of tetracaine was obtained from measurements on frog skeletal muscle fibres. In amphibians the early, inactivating peak of calcium release was suppressed by low (û 20 ìÒ) concentrations of the drug while the maintained steady level was unaffected (Pizarro et al. 1992).