Figure 7.

Recovery from Cl⁻ loading is limited in RT neurons. A, Schematics of protocol for Cl⁻ loading experiments. Neurons were voltage-clamped at −30 mV for 500 ms and then ramped from −100 to −10 mV over a duration of 500 ms (left). This protocol lasted one second and was repeated 100 times per cell (right). After 10 s of baseline recording, Cl⁻ was loaded by applying 10 puffs of muscimol (20 ms, 100 μm), once every 3 s, while the neuron was held at −30 mV. B, Gramicidin perforated patch recordings of RT and VB neurons during measurement of Cl⁻ loading and recovery. E_GABA was measured by finding the point in the voltage ramp where the membrane current responses from before (a) and during (b) muscimol application intersected (marked by dotted line). Cl⁻ recovery was measured by tracking the change in E_GABA following the last application of muscimol (a vs c). Single-exponential functions were fit to the shifting E_GABA occurring in RT (C) and VB (D) neurons to determine time constants for Cl⁻ loading and recovery. E, The change in E_GABA (ΔE_GABA) was measured between the start of Cl⁻ loading and the final reading during Cl⁻ recovery (C, inset). This measurement indicates that chloride loading occurs rapidly in RT neurons. F, The basal Cl⁻ recovery rate (τ_rec) was slower in RT than in VB neurons. The τ_rec in RT neurons was unaffected by a 10 min application of VU0463271 (G, 10 μm), but became slower in VB neurons (H). I, A 2 h incubation in ChABC (0.4 U/ml, 37°C) did not alter the τ_rec of either RT or VB neurons. *p < 0.05, **p < 0.01, ***p < 0.001.