Neuroprotective and neurogenesis agent for treating bipolar II disorder: add-on memantine to mood stabilizer works

Bipolar disorder, characterized by a dysregulation of mood, impulsivity, risky behavior and interpersonal problems, is a recurrent and often becomes chronic psychiatric illness. However, bipolar subtypes are not often recognized in psychiatric settings, especially bipolar II subtype, until Akiskal and Angst made clear definition to bipolar I (BP-I) and bipolar II (BP-II) disorder in 1999. More and more studies, not only on family inheritance, diagnosis, but also on disease process have been reported that BP-I and BP-II are two different disorders with distinct pathological mechanisms. In general, patients with BP-II express less symptoms and have shorter hypomania stages than BP-I. According to a longitudinal research, patients with BP-II have poor recovery than do BP-I patients. Memantine used to be recognized as a noncompetitive N-methyl-d-aspartate receptor antagonist. However, it was found to have neuroprotective and neurogenesis effect in several neurodegenerative diseases in the past years. We found that memantine could inhibit brain inflammatory response through its action on neuroglial cells and provide neurotrophic effect. The above evidences of benefit on auto-immune system with memantine would support that memantine as add-on therapy to valproate might be more effective than valproate alone on improvement of the neuron degeneration in bipolar disorders. Review articles indicate that not only the mood stabilizers provide with good neuroprotection, but the memantine also have conspicuous anti-autoimmune and neurogenesis effect. Therefore, we propose that drugs with neuroprotective effect and neurotrophic effect may treat neurodegenerative diseases including BP-II. The combination treatment of mood stabilizers memantine may not only augment and improve the remedy for bipolar disorders, but also repair the damaged neurons and neurogenesis through activation of astroglial cell and release of neurotrophic factors.