The Journal of Neuroscience, 0000, 20:RC94:1-5
RAPID COMMUNICATION
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
Olivier
Caillard,
Yehezkel
Ben-Ari, and
Jean-Luc
Gaïarsa
Institut de Neurobiologie de la Méditerranée (INMED),
Institut National de la Santé et de la Recherche
Médicale U29, B.P. 13, 13273 Marseille Cedex 09, France
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 GABAA
receptor-mediated postsynaptic responses
(LTDGABA-A). LTDGABA-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 LTDGABA-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 LTDGABA-A.
Altogether, these results suggest that ryanodine acts as a
Ca2+-dependent blocker of CICR stores and that the
induction of LTDGABA-A required the activation of both
presynaptic and postsynaptic CICR stores.
Key words:
synaptic plasticity; development; GABA; glutamate; calcium stores; hippocampus
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