PERMEATION AND GATING OF ALPHA-1 GLYCINE-GATED CHANNELS EXPRESSED AT LOW AND HIGH-DENSITY IN XENOPUS OOCYTE

When a high density of alpha 1-subunit glycine receptor (GlyR) is expr essed in Xenopus oocytes, two populations of channels can be distingui shed according to their apparent affinity for glycine which differs 5- to 6-fold, To compare the open pore diameter of these channels, the r elative permeability of formate with respect to chloride (P-formate/P- Cl) was determined in bionic conditions, For the low-affinity GlyR P-f ormate/P-Cl was comparable to that reported for glycine-gated channels in cultured spinal cord and hippocampal neurons, In contrast, the hig h-affinity GlyR had a 56% larger P-formate/P-Cl, In addition, the open probability of the channels was differentially sensitive to voltage, These results show that the high expression of al GlyR resulted in two populations of GlyR which differed not only in the affinity to agonis ts but also in permeation and gating mechanisms. (C) 1997 Federation o f European Biochemical Societies.