Interaction between the intracellular Ca2+ stores in rat dissociated hippocampal neurones

The interaction between the Ca(2+)-activated K+ currents (IK(Ca)) induced by acetylcholine (ACh), 1-aminocyclopentane-1S,3R-dicarboxylic acid (1S,3R)-ACPD) and caffeine in rat hippocampal CA1 neurones was investigated to examine the functional independence between IP3- and Ca(2+)-sensitive Ca2+ stores. Pretreatment with either ACh or (1S,3R)-ACPD almost completely suppressed the subsequent IK(Ca) induced by another. Pretreatment with caffeine partially suppressed the IK(Ca) induced by either ACh or (1S,3R)-ACPD, although the inhibitory effect varied among the neurones, while pretreatment with either ACh or (1S,3R)-ACPD also partially inhibited the caffeine-induced IK(Ca). Continuous treatment with ryanodine and thapsigargin nonselectively decreased both the caffeine- and ACh-induced IK(Ca). These results thus indicate a close interaction between IP3- and Ca(2+)-sensitive stores and also suggest that the relative size of both stores and the closeness between them differ among neurones.