Figure 4.

MSN membrane properties are not significantly affected after GABA_AR blockade. A–C, Measurement of the input resistance (Ri) before and after bicuculline (20 μm) or PTX (50 μm). Ri was measured with a hyperpolarized pulse (5 pA, 100 ms duration) applied to MSN recorded with regular or high-chloride (136 mm) cesium (Cs⁺)-based intracellular solution (A,B) or during an evoked corticostriatal EPSP. A hyperpolarized pulse (5 mV during 50 ms) was applied to the MSN 5 ms after a cortical stimulation (C). Ri, reflecting the cellular conductance state, did not display significant variation in control or PTX/bicuculline conditions. D, Impedance amplitude profile (ZAP) and resonance value (Q) tested at different holding membrane potentials (−90, −80, and −70 mV) with regular solution did not show any significant variation in control or PTX. There was a slight change when recorded with high-chloride Cs⁺-based intracellular solution. D₁, Illustrative ZAP protocol applied to one MSN in control and with PTX. This protocol consisted of a sinusoidal current of 25 pA amplitude with an increasing frequency from 1 to 100 Hz lasting for 30 s. Below, sample traces of voltage response to the protocol before (black) and after (red) PTX bath application. D₂, Impedance computed as the ratio of the fast Fourier transforms of voltage and current at different membrane potentials (−70, −80, and −90 mV). Inset: Q value at a membrane potential of −80 mV before and after PTX bath application. D₃, MSN impedance at −80 mV using a high chloride and Cs⁺-based internal solution. Inset: resonance at −80 mV before and after PTX bath application. E, F, Kinetics of EPSCs such as rise time or amplitude (E) and EPSP decay time (F) were not significantly affected by PTX or bicuculline treatment.