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Differential control of GABA release at synapses from distinct interneurons in rat hippocampus
Author(s) -
Poncer J. C.,
McKinney R. A.,
Gáhwiler B. H.,
Thompson S. M.
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00123.x
Subject(s) - interneuron , neuroscience , inhibitory postsynaptic potential , gabab receptor , hippocampal formation , agonist , chemistry , biology , receptor , biochemistry
1 Paired recordings from monosynaptically connected CA3 interneurons and pyramidal cells of rat hippocampal slice cultures were used to compare the modulation of GABA release at synapses from distinct interneurons. 2 The group II metabotropic glutamate receptor (mGluR) agonist (2 S ,2′ R ,3′ R) ‐2‐(2′,3′‐dicarboxylcyclopropyl) glycine (DCG‐IV, 5 μ m ) reduced the amplitude of IPSPs originating from stratum radiatum but not stratum oriens interneurons. In contrast, the GABA B receptor agonist (‐)baclofen (10 μ m ) reduced the amplitude of unitary IPSPs elicited by all interneurons. 3 IPSPs mediated by stratum oriens interneurons were unaffected by the N‐type calcium channel blocker ω‐conotoxin MVIIA (1 μ m ) but were suppressed by the P/Q‐type blocker ω‐agatoxin IVA (200 n m ). In contrast, IPSPs mediated by stratum radiatum interneurons were abolished by ω‐conotoxin MVIIA. 4 Transmission dynamics were different at synapses from the two groups of interneurons. IPSPs mediated by stratum oriens interneurons showed marked paired‐pulse depression (PPD) at intervals of 50–400 ms. IPSPs mediated by stratum radiatum interneurons showed paired‐pulse facilitation (PPF) at 50 ms and PPD at longer intervals. 5 The amplitude of unitary IPSPs from all interneurons was unaffected by the GABA B receptor antagonist CGP52432 (2 μ m ) as was PPD at both 50 and 400 ms intervals. However, CGP52432 did reduce PPD of extracellularly evoked IPSPs. 6 Our results show that two groups of inhibitory synapses impinging onto CA3 pyramidal cells can be distinguished according to their dynamic and modulatory properties.