Influence of caffeine on processes of regulation of the intracellular Ca2+ concentration in isolated neurons of the edible snail

Abstract

Changes in the intracellular concentration of Ca2+ ([Ca2+]in) that occur during prolonged depolarization of the plasma membrane were studied in isolated neurons of the edible snailHelix pomatia, using the calcium-sensitive probe Fura-2. The dependence of the amplitude of the calcium response on the value of the depolarization in the presence of 5 mM caffeine, in contrast to that observed in a normal solution, practically disappeared. This fact indicates that caffeine promotes calcium-dependent release of Ca2+ from the intracellular depots, which is the determining factor in the increase in [Ca2+]in during depolarization. Processes of reduction of [Ca2+]in to the steady-state levels were described by one exponential function, and in the presence of caffeine they occurred twice as rapidly as in the normal solution. Such an acceleration of the kinetics of the relaxation of [Ca2+]in is evidently associated with an increase in the efficiency of the work of the calcium pump of the intracellular calcium depots, which might lead to a decrease in the steady-state of level of [Ca2+]in even below the level observed for the normal extracellular solution.