Figure 5. The alkalinization-induced calcium increase is not dependent upon calcium entry.

A typical sample experiment showing the effects of external calcium removal on the response to alkalinization in a voltage-clamped snail neurone. The effects of depolarization (20 steps to 0 mV for 100 ms at 5 Hz), trimethylamine (3 mm) and caffeine (10 mm) on cytosolic calcium were compared in the presence and absence of extracellular calcium. Zero calcium snail Ringer solution contained 1 mm EGTA. All trimethylamine applications were for ∼8 min, caffeine applications were for 1 min.