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Inhibitory transmission in locus coeruleus neurons expressing GABAA receptor epsilon subunit has a number of unique properties.

Abstract：

:Fast inhibitory synaptic transmission in the brain relies on ionotropic GABA(A) receptors (GABA(A)R). Eighteen genes code for GABA(A)R subunits, but little is known about the epsilon subunit. Our aim was to identify the synaptic transmission properties displayed by native receptors incorporating epsilon. Immunogold localization detected epsilon at synaptic sites on locus coeruleus (LC) neurons. In situ hybridization revealed prominent signals from epsilon, and mRNAs, some low beta1 and beta3 signals, and no gamma signal. Using in vivo extracellular and in vitro patch-clamp recordings in LC, we established that neuron firing rates, GABA-activated currents, and mIPSC charge were insensitive to the benzodiazepine flunitrazepam (FLU), in agreement with the characteristics of recombinant receptors including an epsilon subunit. Surprisingly, LC provided binding sites for benzodiazepines, and GABA-induced currents were potentiated by diazepam (DZP) in the micromolar range. A number of GABA(A)R ligands significantly potentiated GABA-induced currents, and zinc ions were only active at concentrations above 1 muM, further indicating that receptors were not composed of only alpha and beta subunits, but included an epsilon subunit. In contrast to recombinant receptors including an epsilon subunit, GABA(A)R in LC showed no agonist-independent opening. Finally, we determined that mIPSCs, as well as ensemble currents induced by ultra-fast GABA application, exhibited surprisingly slow rise times. Our work thus defines the signature of native GABA(A)R with a subunit composition including epsilon: differential sensitivity to FLU and DZP and slow rise time of currents. We further propose that alpha(3,) beta(1/3,) and epsilon subunits compose GABA(A)R in LC.

journal_name

J Neurophysiol

journal_title

Journal of neurophysiology

authors

Belujon P,Baufreton J,Grandoso L,Boué-Grabot E,Batten TF,Ugedo L,Garret M,Taupignon AI

doi

10.1152/jn.00227.2009

subject

Has Abstract

pub_date

2009-10-01 00:00:00

pages

2312-25

issue

eissn

0022-3077

issn

1522-1598

pii

00227.2009

journal_volume

102

pub_type

杂志文章

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Inhibitory transmission in locus coeruleus neurons expressing GABAA receptor epsilon subunit has a number of unique properties.