AMPA RECEPTOR SUBUNITS EXPRESSED BY SINGLE ASTROCYTES IN THE JUVENILEMOUSE HIPPOCAMPUS

The subunit composition of native AR IPA receptor (AMPA-R) channels wa s recently described in several neuronal cell types but less informati on is available on glial cells. Evidence from recombinant receptor stu dies suggests that the expression of distinct subunits determines the specific functional properties of the receptor channel. In the present study, we combined the patch clamp technique with the reverse transcr iption-polymerase chain reaction (RT PCR) to correlate the expression of gene transcripts with functional properties of AMPA-R in single ide ntified glial cells of the hippocampus. The cells were freshly isolate d from the stratum radiatum of the CA1 subregion. We focused on cells expressing AMPA-R with an intermediate Ca2+ permeability which were id entified as immature astrocytes due to their morphological, immunocyto chemical and electrophysiological characteristics. After recording, th e cells were harvested and RT-PCR was performed with the same individu al cell to investigate the composition of their AMPA-R transcripts. Ou r results suggest the expression of a heteromeric subunit architecture . In all cells, the GluR2 subunit was present, which is known to confe r a low Ca2+ permeability to the receptor complex. Most frequently, we met co-expression of GluR2 and GluR4. This study demonstrates that as trocytes in the hippocampus express a distinct AMPA-R subunit composit ion which differs from neurons. The glial receptors might be involved in the modulation of gene expression as well as the regulation of prol iferation and differentiation.