GABAB restrains release from singly-evoked GABA terminals

Y. H. Jin, Michael Andresen

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Neurotransmitter release regulation is highly heterogeneous across the brain. The fundamental units of release, individual boutons, are difficult to access and poorly understood. Here we directly activated single boutons on mechanically isolated nucleus tractus solitarius (NTS) neurons to record unitary synaptic events under voltage clamp. By scanning the cell surface with a stimulating pipette, we located unique sites that generated evoked excitatory postsynaptic currents (eEPSCs) or evoked inhibitory postsynaptic currents (eIPSCs) events. Stimulus-response relations had abrupt thresholds for all-or-none synaptic events consistent with unitary responses. Thus, irrespective of shock intensity, focal stimulation selectively evoked either eEPSCs or eIPSCs from single retained synaptic boutons and never recruited other synapses. Evoked EPSCs were rarely encountered. Our studies, thus, focused primarily on the more common GABA release. At most locations, shocks often failed to release GABA even at low frequencies (0.075 Hz), and eIPSCs succeeded only on average 2.7±0.7 successful IPSCs per 10 shocks. Activation of eIPSCs decreased spontaneous IPSCs in the same neurons. The GABAA receptor antagonist gabazine (3 μM) reversibly blocked eIPSCs as did tetrodotoxin (TTX) (300 nM). The initial low rate of successful eIPSCs decreased further in a use-dependent manner at 0.5 Hz stimulation-depressing 70% in 2 min. The selective GABAB receptor antagonist 3-[[(3,4-Dichlorophenyl)methyl]amino]propyl] diethoxymethyl)phosphinic acid (CGP 52432) (5 μM) had three actions: tripling the initial release rate, slowing the use-dependent decline without changing amplitudes, and blocking the shock-related decrease in spontaneous IPSCs. The results suggest strong, surprisingly long-lasting, negative feedback by GABAB receptors within single GABA terminals that determine release probability even in isolated terminals.

Original languageEnglish (US)
Pages (from-to)54-62
Number of pages9
JournalNeuroscience
Volume193
DOIs
StatePublished - Oct 13 2011

Fingerprint

Inhibitory Postsynaptic Potentials
gamma-Aminobutyric Acid
Shock
Excitatory Postsynaptic Potentials
GABA-A Receptor Antagonists
Neurons
Solitary Nucleus
Tetrodotoxin
Presynaptic Terminals
Synapses
Neurotransmitter Agents
Brain

Keywords

  • Metabotropic
  • Release probability
  • Single bouton
  • Synaptic failures

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

GABAB restrains release from singly-evoked GABA terminals. / Jin, Y. H.; Andresen, Michael.

In: Neuroscience, Vol. 193, 13.10.2011, p. 54-62.

Research output: Contribution to journalArticle

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