Abstract
OBJECTIVE: Lithium is used as first line in treating bipolar patients to stabilize their mood. However, the exact mechanism of lithium is not yet established. One of the proposed mechanisms is that lithium depolarizes the hyperpolarized neuronal membrane of bipolar patients bringing it back to the normal potential. On the other hand, the only way that lithium causes significant therapeutic depolarization is to have a membrane conductance that must be at least an order of magnitude higher than that for sodium but this is not achieved since both; lithium and sodium have the same conductance because the membrane channels are selective for them approximately by the same degree. So, this study aimed to explain how lithium could achieve higher conductance than sodium. METHODS: The idea of quantum tunneling through closed channels was used in a way to calculate the tunneling probability and the quantum conductance for lithium ions. RESULTS: It was found that lithium could achieve higher conductance than sodium because it has a smaller mass than sodium making lithium to have higher probability of tunneling and consequently higher conductance through channels and membrane. CONCLUSION: Lithium tunneling model provides a reasonable explanation for the therapeutic depolarization effect of lithium. This model is experimentally testable to prove the tunneling effect of ions through the closed channels and to show the variations of quantum conductance between ions according to their mass.