Intracellular pH, the amount of acid inside neurons (brain cells) changes during normal cellular activity and with conditions such as stroke. Left unregulated, these changes can alter brain cell function and contribute to their death following a stroke. Consequently, cells have developed mechanisms to maintain their intracellular pH within normal limits. The hippocampus, a part of the brain associated with learning and memory, contains some cells that are very susceptible and some that are very resistant to stroke-related cell death. Research has identified three mechanisms that regulate pH in hippocampal brain cells, but recent evidence suggests that these mechanisms are inhibited during a stroke. May Cheng is investigating whether there is a fourth mechanism, a voltage-gated proton conductance, that regulates pH by discharging detrimental acid from these cells. Identifying this additional mechanism could lead to new strategies to prevent or limit brain cell death following a stroke.