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Is GABA neurotransmission enhanced in auditory thalamus relative to inferior colliculus?
- Source :
-
Journal of neurophysiology [J Neurophysiol] 2014 Jan; Vol. 111 (2), pp. 229-38. Date of Electronic Publication: 2013 Oct 23. - Publication Year :
- 2014
-
Abstract
- Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the central auditory system. Sensory thalamic structures show high levels of non-desensitizing extrasynaptic GABAA receptors (GABAARs) and a reduction in the redundancy of coded information. The present study compared the inhibitory potency of GABA acting at GABAARs between the inferior colliculus (IC) and the medial geniculate body (MGB) using quantitative in vivo, in vitro, and ex vivo experimental approaches. In vivo single unit studies compared the ability of half maximal inhibitory concentrations of GABA to inhibit sound-evoked temporal responses, and found that GABA was two to three times (P < 0.01) more potent at suppressing MGB single unit responses than IC unit responses. In vitro whole cell patch-clamp slice recordings were used to demonstrate that gaboxadol, a δ-subunit selective GABAAR agonist, was significantly more potent at evoking tonic inhibitory currents from MGB neurons than IC neurons (P < 0.01). These electrophysiological findings were supported by an in vitro receptor binding assay which used the picrotoxin analog [(3)H]TBOB to assess binding in the GABAAR chloride channel. MGB GABAARs had significantly greater total open chloride channel capacity relative to GABAARs in IC (P < 0.05) as shown by increased total [(3)H]TBOB binding. Finally, a comparative ex vivo measurement compared endogenous GABA levels and suggested a trend towards higher GABA concentrations in MGB than in IC. Collectively, these studies suggest that, per unit GABA, high affinity extrasynaptic and synaptic GABAARs confer a significant inhibitory GABAAR advantage to MGB neurons relative to IC neurons. This increased GABA sensitivity likely underpins the vital filtering role of auditory thalamus.
- Subjects :
- Animals
Chlorides metabolism
GABA-A Receptor Agonists pharmacology
GABAergic Neurons metabolism
Geniculate Bodies cytology
Geniculate Bodies metabolism
Inferior Colliculi cytology
Inferior Colliculi metabolism
Isoxazoles pharmacology
Male
Rats
Rats, Inbred F344
Rats, Long-Evans
Receptors, GABA-A metabolism
Synapses metabolism
Synapses physiology
GABAergic Neurons physiology
Geniculate Bodies physiology
Inferior Colliculi physiology
Synaptic Potentials
gamma-Aminobutyric Acid metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 1522-1598
- Volume :
- 111
- Issue :
- 2
- Database :
- MEDLINE
- Journal :
- Journal of neurophysiology
- Publication Type :
- Academic Journal
- Accession number :
- 24155003
- Full Text :
- https://doi.org/10.1152/jn.00556.2013