Intracellular calcium: its release from granules during bursting activity in snail neurons.

Pentylenetetrazole induces a bursting activity accompanied by intracellular movement of calcium toward the cell membrane in the snail neuron. The calcium appears to originate from the dense lysosome-like granules in the cytoplasm. Pentylenetetrazole markedly depletes the granules of calcium and alters them ultrastructurally from dense granules to lamella type granules.