Kinetics of GABA B autoreceptor-mediated suppression of GABA release in rat insular cortex

Masayuki Kobayashi, Hiroki Takei, Kiyofumi Yamamoto, Hiroshige Hatanaka, Noriaki Koshikawa

Research output: Contribution to journalArticlepeer-review

37 Citations (Scopus)


Release of GABA is controlled by presynaptic GABA receptor type B (GABA B) autoreceptors at GABAergic terminals. However, there is no direct evidence that GABA B autoreceptors are activated by GABA release from their own terminals, and precise profiles of GABA B autoreceptor-mediated suppression of GABA release remain unknown. To explore these issues, we performed multiple whole-cell, patch-clamp recordings from layer V rat insular cortex. Both unitary inhibitory and excitatory postsynaptic currents (uIPSCs and uEPSCs, respectively) were recorded by applying a five-train depolarizing pulse injection at 20 Hz. In connections from both fast-spiking (FS) and non-FS interneurons to pyramidal cells, the GABA B receptor antagonist CGP 52432 had little effect on the initial uIPSC amplitude. However, uIPSCs, responding to later pulses, were effectively facilitated. This CGP 52432-induced facilitation was prominent in the fourth uIPSCs, which were evoked 150 ms after the first uIPSC. The facilitation of uIPSCs was accompanied by an increase in the pairedpulse ratio. In addition, analysis of the coefficient of variation suggests the involvement of presynaptic mechanisms in CGP 52432-induced uIPSC facilitation. Paired-pulse stimulation (interstimulus interval = 150 ms) of presynaptic FS cells revealed that the second uIPSC was also facilitated by CGP 52432, which had little effect on the amplitude and interevent interval of miniature IPSCs. In contrast, uEPSCs, responding to all five stimulations of a presynaptic pyramidal cell, were less affected by CGP 52432. These results suggest that a single presynaptic action potential is sufficient to activate GABA B autoreceptors and to suppress GABA release in the cerebral cortex.

Original languageEnglish
Pages (from-to)1431-1442
Number of pages12
JournalJournal of Neurophysiology
Issue number5
Publication statusPublished - Mar 2012


  • IPSC
  • Metabotropic receptor
  • Neocortex
  • Presynaptic
  • Release probability


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