Corrêa Sônia A L, Munton Richard, Nishimune Atsushi, Fitzjohn Stephen, Henley Jeremy M
MRC Centre for Synaptic Plasticity, Department of Anatomy, School of Medical Sciences, University of Bristol, University Walk, Bristol BS 1TD, UK.
Neuropharmacology. 2004 Sep;47(4):475-84. doi: 10.1016/j.neuropharm.2004.04.021.
Metabotropic gamma-aminobutyric acid receptors (GABA(B)Rs) play a critical role in inhibitory synaptic transmission in the hippocampus but the ontogeny of their subunit synthesis and synaptic localisation has not been determined. Here we report the distributions and developmental profiles of GABA(B1) and GABA(B2) subunits in cultured rat embryonic hippocampal neurons. Limited levels of GABA(B1) and GABA(B2) immunoreactivity were present at 3 days in vitro (DIV). At 7 DIV, when baclofen-evoked inwardly rectifying K(+) channel-mediated responses first appear in the cells, there was a more widespread expression within the soma and proximal dendrites. Levels of the K(+) channel GIRK 1 were relatively constant at all time points suggesting channel availability does not limit the appearance of functional GABA(B)Rs. At 14 DIV the staining displayed a punctate dendritic distribution and near maximal GABA(B)R-mediated electrophysiological responses were obtained. About half of the puncta for each GABA(B)R subunit in dendrites co-localised with the synaptic marker SV2a suggesting that these subunits are at or very near to synapses. Interestingly, at all ages strong GABA(B)R immunoreactivity was also present in the nuclei of neurons. These results provide an important developmental baseline for future studies aimed at investigating, for example, the trafficking and functional regulation of these receptors.
代谢型γ-氨基丁酸受体（GABA(B)Rs）在海马体的抑制性突触传递中起关键作用，但其亚基合成和突触定位的个体发生尚未确定。在此，我们报告了培养的大鼠胚胎海马神经元中GABA(B1)和GABA(B2)亚基的分布及发育情况。体外培养3天（DIV）时，GABA(B1)和GABA(B2)免疫反应性水平有限。在7 DIV时，当巴氯芬诱发的内向整流钾（K(+)）通道介导的反应首次出现在细胞中时，在胞体和近端树突中有更广泛的表达。钾通道GIRK 1的水平在所有时间点相对恒定，表明通道可用性并不限制功能性GABA(B)Rs的出现。在14 DIV时，染色显示出点状的树突分布，并获得了接近最大的GABA(B)R介导的电生理反应。树突中每个GABA(B)R亚基的约一半点状结构与突触标记物SV2a共定位，表明这些亚基位于突触处或非常接近突触。有趣的是，在所有年龄段，神经元细胞核中也存在强烈的GABA(B)R免疫反应性。这些结果为未来旨在研究例如这些受体的运输和功能调节的研究提供了重要的发育基线。
