Intracellular Ca2+ activity in Helix neurons: Effects of extraellular Ca2+, H+, Na+ AND N−3

Hippocampal long-term potentiation increases mitochondrial calcium pump activity in rat

45Ca2+ pump activity was measured in hippocampal homogenates after the induction of long-term potentiation (LTP) of perforant path-dentate gyrus synapses in vivo. The mitochondrial poison, sodium azide, was used to separate mitochondrial from non-mitochondrial 45Ca2+ uptake. High-frequency stimulation of the perforant path input produced a selectively increased mitochondrial uptake of calcium. This increased pump activity may permit granule cells to more effectively buffer higher intracellular calcium levels associated with LTP.

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.