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Differential distribution of GABA A receptor subunits in soma and processes of cerebellar granule cells: Effects of maturation and a GABA agonist
Author(s) -
Elster Lisbeth,
Hansen Gert H.,
Belhage Bo,
Fritschy Jean M.,
Möhler Hanns,
Schousboe Arne
Publication year - 1995
Publication title -
international journal of developmental neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.761
H-Index - 88
eISSN - 1873-474X
pISSN - 0736-5748
DOI - 10.1016/0736-5748(95)00024-b
Subject(s) - gabaa receptor , receptor , population , agonist , biology , microbiology and biotechnology , immunogold labelling , cerebellum , gabab receptor , protein subunit , gabaa rho receptor , granule cell , neuroscience , chemistry , endocrinology , medicine , biophysics , biochemistry , ultrastructure , anatomy , central nervous system , dentate gyrus , demography , sociology , gene
Quantitative analysis of the density of 1 and β 2/3 GABA A receptor subunits was performed at the electron microscope level after indirect pre‐embedding immunogold labeling with subunit‐specific antibodies of rat cerebellar granule cell cultures grown for 4 or 8 days and in the presence or absence of the GABA A receptor agonist 4,5,6,7‐tetrahydroisoxazolo[5,4 c ]pyridin‐3‐ol (THIP). THIP (150 μM) induced a 2‐fold increase in the number of α 1 and β 2/3 subunits in both cell bodies and processes in 4‐day‐old cultures. Extending the culture period to 8 days led to a polarization of the receptor expression, since the increase in the number of subunits selectively was observed in the processes. Moreover, a general subcellular differentiation of the receptor population was observed in all culture conditions, since the ratio between the two subunits (β 2/3 ;α 1 ) was four times higher in cell bodies compared to processes. A detailed analysis of the less mature (4‐day‐old) cultures revealed the existence of two populations of neurons exhibiting differences in the average number of receptors. During maturation neurons with few receptors developed into cells with a higher density of receptors resulting in a single population of the latter neurons, a process enhanced by exposure to THIP. This may indicate that receptor development is a discontinuous process with individual neurons following different temporal patterns. In double‐labeling experiments, a spatially close association of the α 1 and β 2/3 subunits could be seen, but the subunits were more frequently found separated from each other. In spite of the fact that exposure of the neurons to THIP increased the total number of receptor subunits, its presence apparently prevented formation of receptors with this subunit composition. Interestingly, receptor subunit clusters, consisting of α 1 alone, were more frequently observed than composite ( 1 and β 2/3 ) clusters. This substantiates the view that receptors not having α 1 and β 2/3 subunits in the same complex may exist.