Intracellular Ca2+ activity during slow synaptic hyperpolarizations in Helix pomatia.

In the "bursting" cell RPal of Helix pomatia, intracellular Ca2+ activity increased during the slow synaptic hyperpolarization termed LLH. The Ca2+ increase had a double exponential time course and the kinetics provide evidence for an intracellularly located Ca2+ source. The Ca2+ wave could be mimicked by dopamine and inhibited by ergometrine. dB-cAMP also enhanced the Ca2+ activity. Intracellular K+ was measured during LLH. An appendix by J. D. C. Labmert demonstrates that a dominant mechanism underlying LLH is the increase of K+ permeability.