The extent of GluR5 editing sharply increases from embryonic day 16 through the first postnatal week, correlating well with the time course of the decrease in Ca²⁺permeability. A, Unedited GluR5 decreases over the first postnatal week. After reverse transcription-PCR, isolated GluR5 transcripts were digested by the endonuclease BbvI, separated on polyacrylamide–TBE gels, and stained with ethidium bromide for visualization. The presence of two bottom bands at 139 and 94 bp represents the unedited GluR5 digested by BbvI. The remaining band on thetop at 233 bp represents the amount of edited GluR5.B, The summary of the GluR5-editing assay. The extent of GluR5 editing at the Q/R site is measured by comparing the intensity of the top bands of the − column (noBbvI added) with that of the + column(BbvI added). For each age point, at least three preparations of DRGs were used, except for the adult. Theasterisk indicates a significant difference (based on Student's t test) between E19 and P0 (p < 0.05). The error bars indicate the SEM. There is a progressive increase in the extent of editing until it is essentially complete at P7.