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Glycine receptors and GABA A receptor α1 and γ2 subunits during the development of mouse hypoglossal nucleus
Author(s) -
Muller Emilie,
Triller Antoine,
Legendre Pascal
Publication year - 2004
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1111/j.1460-9568.2004.03785.x
Subject(s) - gephyrin , glycine receptor , inhibitory postsynaptic potential , colocalization , synapse , receptor , biology , gabaa receptor , glycine , microbiology and biotechnology , protein subunit , chemistry , neuroscience , biochemistry , amino acid , gene
In the hypoglossal nucleus, GABA and glycine mediate inhibition at separate or mixed synapses containing glycine receptors (GlyRs) and/or GABA A receptors (GABA A Rs). The functional development of mixed inhibitory synapses depends on the brain area studied, but their relative proportion to total synapses generally decreases with time. We have determined the sequential process of inhibitory synapse maturation in the hypoglossal nucleus in vivo . Immunocytochemistry and confocal microscopy were used for codetection of VIAAT, the common presynaptic vesicular transporter of glycine and GABA, GlyRs, GABA A R α1 and γ2 subunits, and gephyrin, the scaffold protein implicated in the synaptic localization of inhibitory receptors. In E17 embryos, GlyRs were already clustered while GABA A R α1 and γ2 subunit immunoreactivity (IR) displayed both diffuse and clustered patterns. Quantitative analysis at this stage revealed that the majority of GlyR clusters were apposed to VIAAT‐IR accumulation and that 30% of them colocalized with γ2GABA A R clusters. This proportion increased with age to 50% at P30. GlyR clusters that did not colocalize with γ2GABA A R clusters were associated with GABA A R γ2 diffuse IR. Interestingly, the percentage of GlyR clusters surrounded by GABA A R γ2 diffuse IR decreased with age, while GlyR clusters colocalized with γ2GABA A R clusters increased. The developmental coclustered pattern of gephyrin and GABA A R α1 and γ2 subunits paralleled the coclustered pattern of GlyRs and GABA A R α1 and γ2 subunits. Our results indicate that the proportion of GlyR‐GABA A R coclusters increases until adulthood. A developmental sequence of the postsynaptic events is proposed in which diffuse extrasynaptic GABA A Rs accumulate at inhibitory synapses to form postsynaptic clusters, most of them being colocalized with GlyR clusters in the adult.