Beato_2007_J.Physiol_580_497

An essential step in understanding fast synaptic transmission is to establish the activation mechanism of synaptic receptors. The purpose of this work was to extend our detailed single-channel kinetic characterization of alpha1beta glycine channels from rat recombinant receptors to native channels from juvenile (postnatal day 12-16) rat spinal cord slices. In cell-attached patches from ventral horn neurones, 1 mM glycine elicited clusters of channel openings to a single conductance level (41 +/- 1 pS, n = 12). This is similar to that of recombinant heteromers. However, fewer than 1 in 100 cell-attached patches from spinal neurones contained glycine channels. Outside-out patches gave a much higher success rate, but glycine channels recorded in this configuration appeared different, in that clusters opened to three conductance levels (28 +/- 2, 38 +/- 1 and 46 +/- 1 pS, n = 7, one level per cluster, all levels being detected in each patch). Furthermore, open period properties were different for the different conductances. As a consequence of this, the only recordings suitable for kinetic analysis were the cell-attached ones. Low channel density precluded recording at glycine concentrations other than 1 mM, but the 1 mm data allowed us to estimate the fully bound gating constants by global model fitting of the 'flip' mechanism of Burzomato and co-workers. Our results suggest that glycine receptors on ventral horn neurones in the juvenile rat are heteromers and have fast gating, similar to that of recombinant alpha1beta receptors.