GABA mediates presynaptic inhibition at glycinergic synapses in a rat auditory brainstem nucleus
Lim, Rebecca; Alvarez, Francisco; Walmsley, Bruce
Description
1. Many inhibitory nerve terminals in the mammalian anteroventral cochlear nucleus (AVCN) contain both glycine and GABA, but the reason for the co-localization of these two inhibitory neurotransmitters in the AVCN is unknown. We have investigated the roles of glycine and GABA at synapses on bushy cells in the rat AVCN, using receptor immunohistochemistry and electrophysiology. 2. Our immunohistochemical results show prominent punctate labelling of postsynaptic clusters of glycine receptors and...[Show more]
dc.contributor.author | Lim, Rebecca | |
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dc.contributor.author | Alvarez, Francisco | |
dc.contributor.author | Walmsley, Bruce | |
dc.date.accessioned | 2015-12-13T23:16:13Z | |
dc.identifier.issn | 0022-3751 | |
dc.identifier.uri | http://hdl.handle.net/1885/89291 | |
dc.description.abstract | 1. Many inhibitory nerve terminals in the mammalian anteroventral cochlear nucleus (AVCN) contain both glycine and GABA, but the reason for the co-localization of these two inhibitory neurotransmitters in the AVCN is unknown. We have investigated the roles of glycine and GABA at synapses on bushy cells in the rat AVCN, using receptor immunohistochemistry and electrophysiology. 2. Our immunohistochemical results show prominent punctate labelling of postsynaptic clusters of glycine receptors and of the receptor clustering protein gephyrin over the surface of bushy cells. In contrast, weak diffuse membrane immunolabelling of GABA(A) receptors was observed. 3. Whole-cell recordings from bushy cells in AVCN slices demonstrated that evoked inhibitory postsynaptic currents (IPSCs) were predominantly (81%) glycinergic, based on the decrease in amplitude of the IPSCs in bicuculline (10 μM). This observation was supported by the effect of strychnine (1 μM), which was to decrease the evoked IPSC (to 10% of control IPSC amplitude) and to produce a greater than 90% block of spontaneous miniature IPSCs. 4. These results suggest a minor role for postsynaptic GABA(A) receptors in bushy cells, despite a high proportion of GABA-containing terminals on these cells. Therefore, a role for metabotropic GABA(B) receptors was investigated. Activation of GABA(B) receptors with baclofen revealed a significant attenuation of evoked glycinergic IPSCs. The effect of baclofen was presynaptic, as indicated by a lack of change in the mean amplitude of spontaneous IPSCs. 5. Significantly, the decrease in the amplitude of evoked glycinergic IPSCs observed following repetitive nerve stimulation was reduced in the presence of the GABA(B) antagonist, CGP 35348. This indicates that synaptically released GABA can activate presynaptic GABA(B) receptors to reduce transmitter release at glycinergic synapses. Our results suggest specific pre- versus postsynaptic physiological roles for GABA and glycine in the AVCN. | |
dc.publisher | Cambridge University Press | |
dc.source | Journal of Physiology | |
dc.subject | Keywords: 3 aminopropyl(diethoxymethyl)phosphinic acid; 4 aminobutyric acid; 4 aminobutyric acid A receptor; 4 aminobutyric acid B receptor; baclofen; gephyrin; glycine; glycine receptor; neurotransmitter; strychnine; animal tissue; article; brain stem; cochlear nu | |
dc.title | GABA mediates presynaptic inhibition at glycinergic synapses in a rat auditory brainstem nucleus | |
dc.type | Journal article | |
local.description.notes | Imported from ARIES | |
local.description.refereed | Yes | |
local.identifier.citationvolume | 525 | |
dc.date.issued | 2000 | |
local.identifier.absfor | 060105 - Cell Neurochemistry | |
local.identifier.ariespublication | MigratedxPub19261 | |
local.type.status | Published Version | |
local.contributor.affiliation | Lim, Rebecca, College of Medicine, Biology and Environment, ANU | |
local.contributor.affiliation | Alvarez, Francisco, Wright State University | |
local.contributor.affiliation | Walmsley, Bruce, College of Medicine, Biology and Environment, ANU | |
local.description.embargo | 2037-12-31 | |
local.bibliographicCitation.startpage | 447 | |
local.bibliographicCitation.lastpage | 459 | |
dc.date.updated | 2015-12-12T08:47:08Z | |
local.identifier.scopusID | 2-s2.0-0034212866 | |
Collections | ANU Research Publications |
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