Activation of presynaptic and postsynaptic ryanodine-sensitive calcium stores is required for the induction of long-term depression at GABAergic synapses in the neonatal rat hippocampus.
The role of internal calcium stores in the induction of long-term depression at GABAergic synapses was investigated in the neonatal rat hippocampus. Whole-cell recordings of CA3 pyramidal neurons were performed on hippocampal slices from neonatal (2-4 d old) rats. In control conditions, tetanic stimulation (TS) evoked an NMDA-dependent long-term depression of GABA(A) receptor-mediated postsynaptic responses (LTD(GABA-A)). LTD(GABA-A) was prevented when the cells were loaded with ruthenium red, a blocker of Ca2+-induced Ca2+ release (CICR) stores, whereas loading the cells with heparin, a blocker of IP3-induced Ca2+ release stores, had no effect. The effects of ryanodine, another compound that interferes with CICR stores, were also investigated. Intracellular injection of ryanodine prevented the induction of LTD(GABA-A) only when the TS was preceded by depolarizing pulses that increase intracellular Ca2+ concentration. When applied in the bath, ryanodine prevented the induction of LTD(GABA-A). Altogether, these results suggest that ryanodine acts as a Ca2+-dependent blocker of CICR stores and that the induction of LTD(GABA-A) required the activation of both presynaptic and postsynaptic CICR stores.
Caillard
O
O
Institut de Neurobiologie de la Méditerranée, B.P. 13, 13273 Marseille Cedex 09, France. ocailla@gwdg.de
Ben-Ari
Y
Y
Gaïarsa
J L
JL
D000818:Animals; D000831:Animals, Newborn; D002118:Calcium / Q000378:metabolism*; D004396:Coloring Agents / Q000494:pharmacology; D004558:Electric Stimulation; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006493:Heparin / Q000494:pharmacology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D066298:In Vitro Techniques; D016202:N-Methylaspartate / Q000378:metabolism; D009433:Neural Inhibition / Q000187:drug effects / Q000502:physiology*; D009473:Neuronal Plasticity / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D018408:Patch-Clamp Techniques; D017729:Presynaptic Terminals / Q000378:metabolism; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D011963:Receptors, GABA-A / Q000378:metabolism; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism*; D013995:Time; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D004396:Coloring Agents; D011963:Receptors, GABA-A; D012430:Ruthenium Red; D012433:Ryanodine; D005680:gamma-Aminobutyric Acid; D016202:N-Methylaspartate; D006493:Heparin; D002118:Calcium