Memantine administration stimulates serine-phosphorylation of GSK3 in mouse brain. (A) Memantine (50 mg/kg; 1, 2 and 3 h) was administered to mice and protein extracts from the cerebral cortex were immunoblotted with antibodies for phospho-Ser21-GSK3α, phospho-Ser9-GSK3β, and total GSK3α/β. (B) Memantine (50 mg/kg; 2 h) was administered to mice and protein extracts from the hippocampus and striatum were immunoblotted with antibodies for phospho-Ser21-GSK3α and phospho-Ser9-GSK3β. The number of mice tested 1, 2, and 3 h after memantine administration were 3, 4, and 2, respectively.