Fig. 2.

Developmental control of subunit composition indicated by changes in spermine sensitivity.A, B, Families of AMPA receptor-mediated currents at potentials from −75 to +60 mV in 15 mV increments in patches from E11 and E18 neurons. All patches were in the continuous presence of 1 mm intracellular spermine and 60 μm extracellular CTZ. Slowed deactivation inA was inconsistently observed. C, Current– voltage relationship showing, that at positive potentials, there is less inward rectification in E11 (open circles) than in E18 (filled circles) neurons. Currents were normalized to the current amplitude at −60 mV. D, Rectification index, as defined by the ratio of conductance (G) at +30 mV relative to conductance at −60 mV for both E11 (n = 4) and E18 (n = 5) neurons. I–V relationships in patches from E18 neurons (gray bar) are slightly outwardly rectifying (rectification index >1) in the absence of intracellular spermine (n = 3). * indicates rectification ratio significantly less at E18 than E11 (p < 0.001). E11 and spermine-free control data also differed significantly (p < 0.01).