Figure 6.

Stargazin does not affect rectification of GluR4 in the absence of polyamines. (a)​ I-V relationships for homomeric GluR4 receptors with and without stargazin in the absence of spermine. Na₂ATP (20 mM) was included in the patch pipette to chelate endogenous polyamines. The I-V relationships are normalized to the current obtained at −80 mV and show identical outward rectification in the presence and absence of stargazin (n = 5 each; symbols as in b). Vertical error bars denote s.e.m. and fitted lines are fifth-order polynomials. Inset shows a family of GluR4 currents (−80 to +80 mV) in response to application of 10 mM glutamate (indicated by the step). (b) Plots of normalized conductance against voltage for the data shown in a. Fitted lines are drawn according to G = G_min + (G₀ − G_min )exp(V_m /V_c), where G₀ is the conductance at 0 mV, G_min is the minimal conductance (normalized value of 1), and V_c is a constant. Without stargazin, G₀ was 1.14 and V_c 33.5 mV. With stargazin, the respective values were 1.09 and 29.4 mV.