Mini MCAT passage: In vitro membrane potential studies

A scientist is using neurons cultured from the fetal cells of rodents to evaluate the effects of opening and closing ion channels. In his experiments, he opens and closes various known ion channels and evaluates the resulting cell membrane potential.

The scientist also investigates a newly discovered ion channel, ion channel X. The scientist records the resulting membrane potential under different extracellular conditions, when channel X is in an open or closed state, as shown in the table below.