Figure 7. P18 NMDA-EPSCs are insensitive to [Zn²⁺]_o and ifenprodil and show reduced sensitivity to block by [Mg²⁺]_o.

A, two example traces of NMDAR-EPSC recorded at +45 mV under control conditions and during perfusion of 0.5 μm Zn²⁺ (upper, grey trace) or ifenprodil (lower, grey trace). Bar graph summarises this pharmacology under the indicated conditions in P18 mice. The NMDAR-EPSC is insensitive to 0.2–0.5 μm Zn²⁺, ifenprodil (10 μm, Ifen) and the Zn²⁺ chelator TPEN (10 μm) but is blocked by d-AP-5 (50 μm). n= number of cells, indicated on the bars. B, voltage-dependent block by extracellular Mg²⁺ at P11 (upper I–V curve) and P18 (lower I–V curve). Both I–V curves show NMDAR-EPSCs with 1 mm[Mg²⁺]_o (filled squares, averaged data from mouse and rat, n= 5), and for 0.1 mm (filled circles, mouse, n= 3) or nominally Mg²⁺ free (assuming 35 μm contaminating Mg²⁺, open squares, mouse, n= 4). Insets show appropriate example traces at a holding potential of −65 mV for the indicated [Mg²⁺]_o. Continuous lines show data fits by eqn (1) with identical parameters at both ages, except for K_o. V_r= 6 mV, G= 5 μS (normalised), V_o= 15 mV; P11: K_o= 7.5 mm, P18: K_o= 14 mm. Data are means ±s.e.m. Significance was tested using ANOVA, *P < 0.05.