Premium
Localization of the GABA B receptor 1a/b subunit relative to glutamatergic synapses in the dorsal cochlear nucleus of the rat
Author(s) -
Luján Rafael,
Shigemoto Ryuichi,
Kulik Akos,
Juiz José M.
Publication year - 2004
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/cne.20160
Subject(s) - dorsal cochlear nucleus , immunogold labelling , biology , immunocytochemistry , dendritic spine , gabaergic , postsynaptic potential , inhibitory postsynaptic potential , neuroscience , glutamatergic , cochlear nucleus , nucleus , microbiology and biotechnology , glutamate receptor , anatomy , receptor , ultrastructure , biochemistry , endocrinology , hippocampal formation
Metabotropic γ‐aminobutyric acid receptors (GABA B ) are involved in pre‐ and postsynaptic inhibitory effects upon auditory neurons and have been implicated in different aspects of acoustic information processing. To understand better the mechanisms by which GABA B receptors mediate their inhibitory effects, we used pre‐embedding immunocytochemical techniques combined with quantification of immunogold particles to reveal the precise subcellular distribution of the GABA B1 subunit in the rat dorsal cochlear nucleus. At the light microscopic level, GABA B1 was detected in all divisions of the cochlear complex. The most intense immunoreactivity for GABA B1 was found in the dorsal cochlear nucleus, whereas immunoreactivity in the anteroventral and posteroventral cochlear nuclei was very low. In the dorsal cochlear nucleus, a punctate labeling was observed in the superficial (molecular and fusiform cell) layers. At the electron microscopic level, GABA B1 was found at both post‐ and presynaptic locations. Postsynaptically, GABA B1 was localized mainly in the dendritic spines of presumed fusiform cells. Quantitative immunogold immunocytochemistry revealed that the highest concentration of GABA B1 in the plasma membrane was in dendritic spines, followed by dendritic shafts and somata. Thus, the most intense immunoreactivity for GABA B1 was observed in dendritic spines with a high density of immunogold particles at extrasynaptic sites, peaking around 300 nm from glutamatergic synapses. This is in contrast to GABAergic synapses, in which GABA B1 was only occasionally found. Presynaptically, receptor immunoreactivity was detected primarily in axospinous endings, probably from granule cells, in both the active zone and extrasynaptic sites. The localization of GABA B1 relative to synaptic sites in the DCN suggests a role for the receptor in the regulation of dendritic excitability and excitatory inputs. J. Comp. Neurol. 475:36–46, 2004. © 2004 Wiley‐Liss, Inc.