Intracellular Ca 2 + ([Ca 2 + ] i ) changes were measured in cell bodies of cultured rat hippocampal neurones with the fluorescent indicator Fluo-3. In the absence of external Ca 2 + , the cholinergic agonist carbachol (200 μM) and the sarco-endoplasmic reticulum Ca 2 + pump inhibitor thapsigargin (0.4 μM) both transiently elevated [Ca 2 + ] i . A subsequent addition of Ca 2 + into the bathing medium caused a second [Ca 2 + ] i change which was blocked by lanthanum (50 μM). Taken together, these experiments indicate that stores depletion can activate a capacitative Ca 2 + entry pathway in cultured hippocampal neurones and further demonstrate the existence of such a Ca 2 + entry in excitable cells.