SUBUNIT COMPOSITION AT THE SINGLE-CELL LEVEL EXPLAINS FUNCTIONAL-PROPERTIES OF A GLUTAMATE-GATED CHANNEL

The diversity of known glutamate-gated channels has been markedly incr eased by the discovery of multiple subunits and their spliced and edit ed variants. These subunits can potentially form different oligomeric complexes with diverging properties. A crucial question is therefore t o determine the actual subunit composition of naturally occurring glut amate receptors. We have coupled patch-clamp recordings and reverse tr anscription followed by PCR amplification to correlate the presence of mRNAs for each subunit and the functional properties of native glutam ate receptors at the single-cell level. In a homogeneous population of functionally identified hippocampal neurons (type II) in culture bear ing a glutamate receptor of the AMPA subtype with a high calcium perme ability, we found that, among the multiple subunits, only two, the flo p forms of CluR1 and CluR4, were expressed. In particular, GluR2 was n ever detected. This composition explains the,uncommon properties of AM PA receptors in type II neurons.