Figure 5. Embryonic maturation of GABA_AR-related effects on membrane potential.

A1 and B1, perforated patch clamp recordings showing currents evoked by brief application of isoguvacine, from different holding potentials, at E13.5 (A1) and E16.5 (B1). Current versus voltage plots (same neurons shown in A1 and B1) allowing calculation of GABA_AR equilibrium potential: −33 mV at E13.5 (A2) and −50 mV at E16.5 (B2) (measured by linear regression analysis, r² > 0.96 in both cases). C, evolution of corrected V_rest (white circles), spike threshold (grey triangles) and E_Cl (black circles) in motoneurons during embryonic development. From E13.5 to E15.5, spike threshold and E_Cl are not significantly different (non-parametric unpaired t test), whereas from E16.5 to birth, E_Cl is significantly lower than spike threshold (**P < 0.01; ***P < 0.0001). Values are means ±s.e.m. (n values indicated in Table 2).