Expression of VRAC currents in CA1 pyramidal neurons in hippocampal slices.

A, Shows a hypoosmotic medium -activated -chloride conductance (HAC) from a pyramidal neuron. After initial recording in the isoosmotic medium (iso, dashed line) as control, the perfusion was switched to the hypoosmotic medium (hypo, −50 mOsm) for 60 min. The neuronal Na+, Ca2+ and K+ channel conductances were pharmacologically inhibited (see Methods). The cell was held at −40 mV in the resting condition, and a pair of alternate voltage pulses at ±40 mV was delivered to the cell every 15 second. Each test pulse in the pair was 1 second long and was separated from each other by 300 ms at −40 mV resting voltage (see the shadowed inset in A for protocol). Because each series of paired alternate pulses was delivered every 15 s, the time scale bar shown under A includes all the unrecorded time periods, or the duration of alternate pulses induced currents are not proportional to the applied time scale. A progressive increase of chloride conductance was recorded over a 60 min of hypo exposure. B. A whole-cell chloride conductance recording with 30 min of hypo exposure. The HAC slowly inactivated after switching the perfusion to the iso. In the same recording, a voltage step protocol was delivered to the cell at the times indicated as “a”, “b” and “c” that represent the chloride currents at control, HAC and recovery, respectively. The I-V curves in C were at times of “a” and “b” and constructed by plotting the steady-state currents against the applied voltages, ranging from −100 mV to +100 mV in a 20 mV increments (see shadowed inset in B). In all the I-V curves in C, the chloride conductance was outwardly rectifying and reversed at around −40 mV.