- 1. Biogenic Amine Hypothesis: Lithium may exert its therapeutic effect by modifying membrane excitability via an ionic mechanism. Intriguing, yet inconsistent
- evidence that Li+ competes for Ca2+ binding sites
2. Electrolyte Hypothesis: Biogenic Amine Hypothesis Li act with monomine. Lithium’s actions may be related to its ability to modulate serotonin and/or norepinephrine function
3. 2nd Messenger System Hypothesis: “Lithium alters the transduction of the neurotransmitter-initiated signal by modifying the function of second messengers". Lithium may reduce the post-synaptic actions of 5-HT and NE on second messenger systems.