期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1999
卷号：96
期号：3
页码：1118-1122
DOI：10.1073/pnas.96.3.1118
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Mossy fiber synapses form the major excitatory input into the autoassociative network of pyramidal cells in the CA3 area of the hippocampus. Here we demonstrate that at the mossy fiber synapses, glutamate and {gamma}-aminobutyric acid (GABA) act as autaptic and heterosynaptic presynaptic inhibitory transmitters through metabotropic glutamate receptors (mGluRs) and GABAB receptors, respectively. Both GABAB receptors and mGluRs are activated through spillover from adjacent synapses. We demonstrate that glutamate spillover caused by brief tetanic activation of mossy fiber terminals remains intact at physiological temperatures. The activation of GABAB receptors increased the threshold for mossy fiber long-term potentiation (LTP), whereas activation of mGluRs did not have such an effect. We speculate that this heterosynaptic depression provides the mossy fiber synapses with a mechanism to efficiently shape input patterns into CA3, increasing the sparseness of the mossy fiber signal and enhancing the capacity and performance of the CA3 associative network. The increase in LTP threshold through activation of presynaptic inhibitory receptors imparts a piesynoptic associative nature to mossy fiber LTP.
