Developmental change of GABAA receptor-mediated current in rat hippocampus
Section snippets
Slice preparation
Hippocampal slices were prepared from Wister rats aged 2–4 days (neonates) or 18–38 days (adults). All experimental protocols were performed in accordance with the guidelines for animal research of the Physiological Society of Japan. All efforts were made to minimize animal suffering and to reduce the number of animals used. Following diethyl ether anesthesia, the animals were decapitated and the brains were removed and cooled in artificial cerebrospinal fluid (ACSF, composition in mM: NaCl
Effect of zolpidem and diazepam on the spontaneous inhibitory postsynaptic current
The spontaneous IPSCs (sIPSCs) were recorded in CA3 pyramidal neurons of hippocampal slices in the presence of excitatory amino acid receptor blockers CNQX (10 μM) and d-APV (50 μM) or d/l-APV (100 μM). Addition of 5 μM bicuculline to perfusing solution blocked all of the sIPSCs under these experimental conditions, indicating that the currents were mediated by GABAA receptor. The GABAergic sIPSCs recorded from neonatal neurons decayed significantly more slowly than that recorded from adult neurons (
Discussion
The present study demonstrates that both spontaneous and evoked IPSCs in hippocampal CA3 region undergo postnatal change in pharmacological and kinetic properties. The decay time-constant was slower in neonatal hippocampus, consistent with a previous report on GABAAergic miniature IPSC in dentate granule cells.11 Prolongation of decay time and low sensitivity to zolpidem of the neonatal GABAergic currents are probably explicable by subunit substitution of GABAA receptors. In heterologous
Acknowledgements
This work was supported in part by Grant-in-Aid (07279105) for Scientific Research on Priority Areas on “Functional Development of Neural Circuits”, the Ministry of Education, Science, Sports and Culture of Japan, and also by Research for the Future Project 96L00310 program from the Japan Society for the Promotion of Science.
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